add cron fork (#31)

cron/.gitignore

@@ -0,0 +1,22 @@
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe

cron/.travis.yml

@@ -0,0 +1 @@
+language: go

cron/LICENSE

@@ -0,0 +1,21 @@
+Copyright (C) 2012 Rob Figueiredo
+All Rights Reserved.
+
+MIT LICENSE
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

cron/README.md

@@ -0,0 +1,23 @@
+# Cron
+
+This package is a fork of [`github.com/robfig/cron/v3@v3.0.0`](https://github.com/robfig/cron/) which adds support for mocking the time using [`github.com/benbjohnson/clock`](https://github.com/benbjohnson/clock)
+
+See [LICENSE](./LICENSE) for the license of the original package.
+
+<!--
+TODO : Remove this package if this PR gets merged https://github.com/robfig/cron/pull/327
+-->
+
+## Using Cron with Mock Clock
+
+```go
+import "github.com/benbjohnson/clock"
+
+clk := clock.NewMock()
+c := cron.New(cron.WithClock(clk))
+c.AddFunc("@every 1h", func() {
+ fmt.Println("Every hour")
+})
+c.Start()
+clk.Add(1 * time.Hour)
+```

cron/chain.go

@@ -0,0 +1,120 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import (
+	"fmt"
+	"runtime"
+	"sync"
+	"time"
+
+	"github.com/benbjohnson/clock"
+)
+
+// JobWrapper decorates the given Job with some behavior.
+type JobWrapper func(Job) Job
+
+// Chain is a sequence of JobWrappers that decorates submitted jobs with
+// cross-cutting behaviors like logging or synchronization.
+type Chain struct {
+	wrappers []JobWrapper
+}
+
+// NewChain returns a Chain consisting of the given JobWrappers.
+func NewChain(c ...JobWrapper) Chain {
+	return Chain{c}
+}
+
+// Then decorates the given job with all JobWrappers in the chain.
+//
+// This:
+//
+//	NewChain(m1, m2, m3).Then(job)
+//
+// is equivalent to:
+//
+//	m1(m2(m3(job)))
+func (c Chain) Then(j Job) Job {
+	for i := range c.wrappers {
+		j = c.wrappers[len(c.wrappers)-i-1](j)
+	}
+	return j
+}
+
+// Recover panics in wrapped jobs and log them with the provided logger.
+func Recover(logger Logger) JobWrapper {
+	return func(j Job) Job {
+		return FuncJob(func() {
+			defer func() {
+				if r := recover(); r != nil {
+					const size = 64 << 10
+					buf := make([]byte, size)
+					buf = buf[:runtime.Stack(buf, false)]
+					err, ok := r.(error)
+					if !ok {
+						err = fmt.Errorf("%v", r)
+					}
+					logger.Error(err, "panic", "stack", "...\n"+string(buf))
+				}
+			}()
+			j.Run()
+		})
+	}
+}
+
+// DelayIfStillRunning serializes jobs, delaying subsequent runs until the
+// previous one is complete. Jobs running after a delay of more than a minute
+// have the delay logged at Info.
+func DelayIfStillRunning(logger Logger) JobWrapper {
+	return DelayIfStillRunningWithClock(logger, clock.New())
+}
+
+// DelayIfStillRunningWithClock behaves identically to DelayIfStillRunning but
+// uses the provided Clock for measuring the delay, for use in testing.
+func DelayIfStillRunningWithClock(logger Logger, clk clock.Clock) JobWrapper {
+	return func(j Job) Job {
+		var mu sync.Mutex
+		return FuncJob(func() {
+			start := clk.Now()
+			mu.Lock()
+			defer mu.Unlock()
+			if dur := clk.Since(start); dur > time.Minute {
+				logger.Info("delay", "duration", dur)
+			}
+			j.Run()
+		})
+	}
+}
+
+// SkipIfStillRunning skips an invocation of the Job if a previous invocation is
+// still running. It logs skips to the given logger at Info level.
+func SkipIfStillRunning(logger Logger) JobWrapper {
+	return func(j Job) Job {
+		ch := make(chan struct{}, 1)
+		ch <- struct{}{}
+		return FuncJob(func() {
+			select {
+			case v := <-ch:
+				j.Run()
+				ch <- v
+			default:
+				logger.Info("skip")
+			}
+		})
+	}
+}

cron/chain_test.go

@@ -0,0 +1,255 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import (
+	"io/ioutil"
+	"log"
+	"reflect"
+	"sync"
+	"testing"
+	"time"
+)
+
+func appendingJob(slice *[]int, value int) Job {
+	var m sync.Mutex
+	return FuncJob(func() {
+		m.Lock()
+		*slice = append(*slice, value)
+		m.Unlock()
+	})
+}
+
+func appendingWrapper(slice *[]int, value int) JobWrapper {
+	return func(j Job) Job {
+		return FuncJob(func() {
+			appendingJob(slice, value).Run()
+			j.Run()
+		})
+	}
+}
+
+func TestChain(t *testing.T) {
+	var nums []int
+	var (
+		append1 = appendingWrapper(&nums, 1)
+		append2 = appendingWrapper(&nums, 2)
+		append3 = appendingWrapper(&nums, 3)
+		append4 = appendingJob(&nums, 4)
+	)
+	NewChain(append1, append2, append3).Then(append4).Run()
+	if !reflect.DeepEqual(nums, []int{1, 2, 3, 4}) {
+		t.Error("unexpected order of calls:", nums)
+	}
+}
+
+func TestChainRecover(t *testing.T) {
+	panickingJob := FuncJob(func() {
+		panic("panickingJob panics")
+	})
+
+	t.Run("panic exits job by default", func(t *testing.T) {
+		defer func() {
+			if err := recover(); err == nil {
+				t.Errorf("panic expected, but none received")
+			}
+		}()
+		NewChain().Then(panickingJob).
+			Run()
+	})
+
+	t.Run("Recovering JobWrapper recovers", func(t *testing.T) {
+		NewChain(Recover(PrintfLogger(log.New(ioutil.Discard, "", 0)))).
+			Then(panickingJob).
+			Run()
+	})
+
+	t.Run("composed with the *IfStillRunning wrappers", func(t *testing.T) {
+		NewChain(Recover(PrintfLogger(log.New(ioutil.Discard, "", 0)))).
+			Then(panickingJob).
+			Run()
+	})
+}
+
+type countJob struct {
+	m       sync.Mutex
+	started int
+	done    int
+	delay   time.Duration
+}
+
+func (j *countJob) Run() {
+	j.m.Lock()
+	j.started++
+	j.m.Unlock()
+	time.Sleep(j.delay)
+	j.m.Lock()
+	j.done++
+	j.m.Unlock()
+}
+
+func (j *countJob) Started() int {
+	defer j.m.Unlock()
+	j.m.Lock()
+	return j.started
+}
+
+func (j *countJob) Done() int {
+	defer j.m.Unlock()
+	j.m.Lock()
+	return j.done
+}
+
+func TestChainDelayIfStillRunning(t *testing.T) {
+	t.Run("runs immediately", func(t *testing.T) {
+		var j countJob
+		wrappedJob := NewChain(DelayIfStillRunning(DiscardLogger)).Then(&j)
+		go wrappedJob.Run()
+		time.Sleep(2 * time.Millisecond) // Give the job 2ms to complete.
+		if c := j.Done(); c != 1 {
+			t.Errorf("expected job run once, immediately, got %d", c)
+		}
+	})
+
+	t.Run("second run immediate if first done", func(t *testing.T) {
+		var j countJob
+		wrappedJob := NewChain(DelayIfStillRunning(DiscardLogger)).Then(&j)
+		go func() {
+			go wrappedJob.Run()
+			time.Sleep(time.Millisecond)
+			go wrappedJob.Run()
+		}()
+		time.Sleep(3 * time.Millisecond) // Give both jobs 3ms to complete.
+		if c := j.Done(); c != 2 {
+			t.Errorf("expected job run twice, immediately, got %d", c)
+		}
+	})
+
+	t.Run("second run delayed if first not done", func(t *testing.T) {
+		var j countJob
+		j.delay = 10 * time.Millisecond
+		wrappedJob := NewChain(DelayIfStillRunning(DiscardLogger)).Then(&j)
+		go func() {
+			go wrappedJob.Run()
+			time.Sleep(time.Millisecond)
+			go wrappedJob.Run()
+		}()
+
+		// After 5ms, the first job is still in progress, and the second job was
+		// run but should be waiting for it to finish.
+		time.Sleep(5 * time.Millisecond)
+		started, done := j.Started(), j.Done()
+		if started != 1 || done != 0 {
+			t.Error("expected first job started, but not finished, got", started, done)
+		}
+
+		// Verify that the second job completes.
+		time.Sleep(25 * time.Millisecond)
+		started, done = j.Started(), j.Done()
+		if started != 2 || done != 2 {
+			t.Error("expected both jobs done, got", started, done)
+		}
+	})
+}
+
+func TestChainSkipIfStillRunning(t *testing.T) {
+	t.Run("runs immediately", func(t *testing.T) {
+		var j countJob
+		wrappedJob := NewChain(SkipIfStillRunning(DiscardLogger)).Then(&j)
+		go wrappedJob.Run()
+		time.Sleep(2 * time.Millisecond) // Give the job 2ms to complete.
+		if c := j.Done(); c != 1 {
+			t.Errorf("expected job run once, immediately, got %d", c)
+		}
+	})
+
+	t.Run("second run immediate if first done", func(t *testing.T) {
+		var j countJob
+		wrappedJob := NewChain(SkipIfStillRunning(DiscardLogger)).Then(&j)
+		go func() {
+			go wrappedJob.Run()
+			time.Sleep(time.Millisecond)
+			go wrappedJob.Run()
+		}()
+		time.Sleep(3 * time.Millisecond) // Give both jobs 3ms to complete.
+		if c := j.Done(); c != 2 {
+			t.Errorf("expected job run twice, immediately, got %d", c)
+		}
+	})
+
+	t.Run("second run skipped if first not done", func(t *testing.T) {
+		var j countJob
+		j.delay = 10 * time.Millisecond
+		wrappedJob := NewChain(SkipIfStillRunning(DiscardLogger)).Then(&j)
+		go func() {
+			go wrappedJob.Run()
+			time.Sleep(time.Millisecond)
+			go wrappedJob.Run()
+		}()
+
+		// After 5ms, the first job is still in progress, and the second job was
+		// aleady skipped.
+		time.Sleep(5 * time.Millisecond)
+		started, done := j.Started(), j.Done()
+		if started != 1 || done != 0 {
+			t.Error("expected first job started, but not finished, got", started, done)
+		}
+
+		// Verify that the first job completes and second does not run.
+		time.Sleep(25 * time.Millisecond)
+		started, done = j.Started(), j.Done()
+		if started != 1 || done != 1 {
+			t.Error("expected second job skipped, got", started, done)
+		}
+	})
+
+	t.Run("skip 10 jobs on rapid fire", func(t *testing.T) {
+		var j countJob
+		j.delay = 10 * time.Millisecond
+		wrappedJob := NewChain(SkipIfStillRunning(DiscardLogger)).Then(&j)
+		for i := 0; i < 11; i++ {
+			go wrappedJob.Run()
+		}
+		time.Sleep(200 * time.Millisecond)
+		done := j.Done()
+		if done != 1 {
+			t.Error("expected 1 jobs executed, 10 jobs dropped, got", done)
+		}
+	})
+
+	t.Run("different jobs independent", func(t *testing.T) {
+		var j1, j2 countJob
+		j1.delay = 10 * time.Millisecond
+		j2.delay = 10 * time.Millisecond
+		chain := NewChain(SkipIfStillRunning(DiscardLogger))
+		wrappedJob1 := chain.Then(&j1)
+		wrappedJob2 := chain.Then(&j2)
+		for i := 0; i < 11; i++ {
+			go wrappedJob1.Run()
+			go wrappedJob2.Run()
+		}
+		time.Sleep(100 * time.Millisecond)
+		var (
+			done1 = j1.Done()
+			done2 = j2.Done()
+		)
+		if done1 != 1 || done2 != 1 {
+			t.Error("expected both jobs executed once, got", done1, "and", done2)
+		}
+	})
+}

cron/constantdelay.go

@@ -0,0 +1,44 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import "time"
+
+// ConstantDelaySchedule represents a simple recurring duty cycle, e.g. "Every 5 minutes".
+// It does not support jobs more frequent than once a second.
+type ConstantDelaySchedule struct {
+	Delay time.Duration
+}
+
+// Every returns a crontab Schedule that activates once every duration.
+// Delays of less than a second are not supported (will round up to 1 second).
+// Any fields less than a Second are truncated.
+func Every(duration time.Duration) ConstantDelaySchedule {
+	if duration < time.Second {
+		duration = time.Second
+	}
+	return ConstantDelaySchedule{
+		Delay: duration - time.Duration(duration.Nanoseconds())%time.Second,
+	}
+}
+
+// Next returns the next time this should be run.
+// This rounds so that the next activation time will be on the second.
+func (schedule ConstantDelaySchedule) Next(t time.Time) time.Time {
+	return t.Add(schedule.Delay - time.Duration(t.Nanosecond())*time.Nanosecond)
+}

cron/constantdelay_test.go

@@ -0,0 +1,71 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import (
+	"testing"
+	"time"
+)
+
+func TestConstantDelayNext(t *testing.T) {
+	tests := []struct {
+		time     string
+		delay    time.Duration
+		expected string
+	}{
+		// Simple cases
+		{"Mon Jul 9 14:45 2012", 15*time.Minute + 50*time.Nanosecond, "Mon Jul 9 15:00 2012"},
+		{"Mon Jul 9 14:59 2012", 15 * time.Minute, "Mon Jul 9 15:14 2012"},
+		{"Mon Jul 9 14:59:59 2012", 15 * time.Minute, "Mon Jul 9 15:14:59 2012"},
+
+		// Wrap around hours
+		{"Mon Jul 9 15:45 2012", 35 * time.Minute, "Mon Jul 9 16:20 2012"},
+
+		// Wrap around days
+		{"Mon Jul 9 23:46 2012", 14 * time.Minute, "Tue Jul 10 00:00 2012"},
+		{"Mon Jul 9 23:45 2012", 35 * time.Minute, "Tue Jul 10 00:20 2012"},
+		{"Mon Jul 9 23:35:51 2012", 44*time.Minute + 24*time.Second, "Tue Jul 10 00:20:15 2012"},
+		{"Mon Jul 9 23:35:51 2012", 25*time.Hour + 44*time.Minute + 24*time.Second, "Thu Jul 11 01:20:15 2012"},
+
+		// Wrap around months
+		{"Mon Jul 9 23:35 2012", 91*24*time.Hour + 25*time.Minute, "Thu Oct 9 00:00 2012"},
+
+		// Wrap around minute, hour, day, month, and year
+		{"Mon Dec 31 23:59:45 2012", 15 * time.Second, "Tue Jan 1 00:00:00 2013"},
+
+		// Round to nearest second on the delay
+		{"Mon Jul 9 14:45 2012", 15*time.Minute + 50*time.Nanosecond, "Mon Jul 9 15:00 2012"},
+
+		// Round up to 1 second if the duration is less.
+		{"Mon Jul 9 14:45:00 2012", 15 * time.Millisecond, "Mon Jul 9 14:45:01 2012"},
+
+		// Round to nearest second when calculating the next time.
+		{"Mon Jul 9 14:45:00.005 2012", 15 * time.Minute, "Mon Jul 9 15:00 2012"},
+
+		// Round to nearest second for both.
+		{"Mon Jul 9 14:45:00.005 2012", 15*time.Minute + 50*time.Nanosecond, "Mon Jul 9 15:00 2012"},
+	}
+
+	for _, c := range tests {
+		actual := Every(c.delay).Next(getTime(c.time))
+		expected := getTime(c.expected)
+		if actual != expected {
+			t.Errorf("%s, \"%s\": (expected) %v != %v (actual)", c.time, c.delay, expected, actual)
+		}
+	}
+}

cron/cron.go

@@ -0,0 +1,376 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import (
+	"context"
+	"sort"
+	"sync"
+	"time"
+
+	"github.com/benbjohnson/clock"
+)
+
+// Cron keeps track of any number of entries, invoking the associated func as
+// specified by the schedule. It may be started, stopped, and the entries may
+// be inspected while running.
+type Cron struct {
+	entries   []*Entry
+	chain     Chain
+	stop      chan struct{}
+	add       chan *Entry
+	remove    chan EntryID
+	snapshot  chan chan []Entry
+	running   bool
+	logger    Logger
+	runningMu sync.Mutex
+	location  *time.Location
+	parser    ScheduleParser
+	nextID    EntryID
+	jobWaiter sync.WaitGroup
+	clk       clock.Clock
+}
+
+// ScheduleParser is an interface for schedule spec parsers that return a Schedule
+type ScheduleParser interface {
+	Parse(spec string) (Schedule, error)
+}
+
+// Job is an interface for submitted cron jobs.
+type Job interface {
+	Run()
+}
+
+// Schedule describes a job's duty cycle.
+type Schedule interface {
+	// Next returns the next activation time, later than the given time.
+	// Next is invoked initially, and then each time the job is run.
+	Next(time.Time) time.Time
+}
+
+// EntryID identifies an entry within a Cron instance
+type EntryID int
+
+// Entry consists of a schedule and the func to execute on that schedule.
+type Entry struct {
+	// ID is the cron-assigned ID of this entry, which may be used to look up a
+	// snapshot or remove it.
+	ID EntryID
+
+	// Schedule on which this job should be run.
+	Schedule Schedule
+
+	// Next time the job will run, or the zero time if Cron has not been
+	// started or this entry's schedule is unsatisfiable
+	Next time.Time
+
+	// Prev is the last time this job was run, or the zero time if never.
+	Prev time.Time
+
+	// WrappedJob is the thing to run when the Schedule is activated.
+	WrappedJob Job
+
+	// Job is the thing that was submitted to cron.
+	// It is kept around so that user code that needs to get at the job later,
+	// e.g. via Entries() can do so.
+	Job Job
+}
+
+// Valid returns true if this is not the zero entry.
+func (e Entry) Valid() bool { return e.ID != 0 }
+
+// byTime is a wrapper for sorting the entry array by time
+// (with zero time at the end).
+type byTime []*Entry
+
+func (s byTime) Len() int      { return len(s) }
+func (s byTime) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+func (s byTime) Less(i, j int) bool {
+	// Two zero times should return false.
+	// Otherwise, zero is "greater" than any other time.
+	// (To sort it at the end of the list.)
+	if s[i].Next.IsZero() {
+		return false
+	}
+	if s[j].Next.IsZero() {
+		return true
+	}
+	return s[i].Next.Before(s[j].Next)
+}
+
+// New returns a new Cron job runner, modified by the given options.
+//
+// Available Settings
+//
+//	Time Zone
+//	  Description: The time zone in which schedules are interpreted
+//	  Default:     time.Local
+//
+//	Parser
+//	  Description: Parser converts cron spec strings into cron.Schedules.
+//	  Default:     Accepts this spec: https://en.wikipedia.org/wiki/Cron
+//
+//	Chain
+//	  Description: Wrap submitted jobs to customize behavior.
+//	  Default:     A chain that recovers panics and logs them to stderr.
+//
+// See "cron.With*" to modify the default behavior.
+func New(opts ...Option) *Cron {
+	c := &Cron{
+		entries:   nil,
+		chain:     NewChain(),
+		add:       make(chan *Entry),
+		stop:      make(chan struct{}),
+		snapshot:  make(chan chan []Entry),
+		remove:    make(chan EntryID),
+		running:   false,
+		runningMu: sync.Mutex{},
+		logger:    DefaultLogger,
+		location:  time.Local,
+		parser:    standardParser,
+		clk:       clock.New(),
+	}
+	for _, opt := range opts {
+		opt(c)
+	}
+	return c
+}
+
+// FuncJob is a wrapper that turns a func() into a cron.Job
+type FuncJob func()
+
+func (f FuncJob) Run() { f() }
+
+// AddFunc adds a func to the Cron to be run on the given schedule.
+// The spec is parsed using the time zone of this Cron instance as the default.
+// An opaque ID is returned that can be used to later remove it.
+func (c *Cron) AddFunc(spec string, cmd func()) (EntryID, error) {
+	return c.AddJob(spec, FuncJob(cmd))
+}
+
+// AddJob adds a Job to the Cron to be run on the given schedule.
+// The spec is parsed using the time zone of this Cron instance as the default.
+// An opaque ID is returned that can be used to later remove it.
+func (c *Cron) AddJob(spec string, cmd Job) (EntryID, error) {
+	schedule, err := c.parser.Parse(spec)
+	if err != nil {
+		return 0, err
+	}
+	return c.Schedule(schedule, cmd), nil
+}
+
+// Schedule adds a Job to the Cron to be run on the given schedule.
+// The job is wrapped with the configured Chain.
+func (c *Cron) Schedule(schedule Schedule, cmd Job) EntryID {
+	c.runningMu.Lock()
+	defer c.runningMu.Unlock()
+	c.nextID++
+	entry := &Entry{
+		ID:         c.nextID,
+		Schedule:   schedule,
+		WrappedJob: c.chain.Then(cmd),
+		Job:        cmd,
+	}
+	if !c.running {
+		c.entries = append(c.entries, entry)
+	} else {
+		c.add <- entry
+	}
+	return entry.ID
+}
+
+// Entries returns a snapshot of the cron entries.
+func (c *Cron) Entries() []Entry {
+	c.runningMu.Lock()
+	defer c.runningMu.Unlock()
+	if c.running {
+		replyChan := make(chan []Entry, 1)
+		c.snapshot <- replyChan
+		return <-replyChan
+	}
+	return c.entrySnapshot()
+}
+
+// Location gets the time zone location
+func (c *Cron) Location() *time.Location {
+	return c.location
+}
+
+// Entry returns a snapshot of the given entry, or nil if it couldn't be found.
+func (c *Cron) Entry(id EntryID) Entry {
+	for _, entry := range c.Entries() {
+		if id == entry.ID {
+			return entry
+		}
+	}
+	return Entry{}
+}
+
+// Remove an entry from being run in the future.
+func (c *Cron) Remove(id EntryID) {
+	c.runningMu.Lock()
+	defer c.runningMu.Unlock()
+	if c.running {
+		c.remove <- id
+	} else {
+		c.removeEntry(id)
+	}
+}
+
+// Start the cron scheduler in its own goroutine, or no-op if already started.
+func (c *Cron) Start() {
+	c.runningMu.Lock()
+	defer c.runningMu.Unlock()
+	if c.running {
+		return
+	}
+	c.running = true
+	go c.run()
+}
+
+// Run the cron scheduler, or no-op if already running.
+func (c *Cron) Run() {
+	c.runningMu.Lock()
+	if c.running {
+		c.runningMu.Unlock()
+		return
+	}
+	c.running = true
+	c.runningMu.Unlock()
+	c.run()
+}
+
+// run the scheduler.. this is private just due to the need to synchronize
+// access to the 'running' state variable.
+func (c *Cron) run() {
+	c.logger.Info("start")
+
+	// Figure out the next activation times for each entry.
+	now := c.now()
+	for _, entry := range c.entries {
+		entry.Next = entry.Schedule.Next(now)
+		c.logger.Info("schedule", "now", now, "entry", entry.ID, "next", entry.Next)
+	}
+
+	for {
+		// Determine the next entry to run.
+		sort.Sort(byTime(c.entries))
+
+		var timer *clock.Timer
+		if len(c.entries) == 0 || c.entries[0].Next.IsZero() {
+			// If there are no entries yet, just sleep - it still handles new entries
+			// and stop requests.
+			timer = c.clk.Timer(100000 * time.Hour)
+		} else {
+			timer = c.clk.Timer(c.entries[0].Next.Sub(now))
+		}
+
+		for {
+			select {
+			case now = <-timer.C:
+				now = now.In(c.location)
+				c.logger.Info("wake", "now", now)
+
+				// Run every entry whose next time was less than now
+				for _, e := range c.entries {
+					if e.Next.After(now) || e.Next.IsZero() {
+						break
+					}
+					c.startJob(e.WrappedJob)
+					e.Prev = e.Next
+					e.Next = e.Schedule.Next(now)
+					c.logger.Info("run", "now", now, "entry", e.ID, "next", e.Next)
+				}
+
+			case newEntry := <-c.add:
+				timer.Stop()
+				now = c.now()
+				newEntry.Next = newEntry.Schedule.Next(now)
+				c.entries = append(c.entries, newEntry)
+				c.logger.Info("added", "now", now, "entry", newEntry.ID, "next", newEntry.Next)
+
+			case replyChan := <-c.snapshot:
+				replyChan <- c.entrySnapshot()
+				continue
+
+			case <-c.stop:
+				timer.Stop()
+				c.logger.Info("stop")
+				return
+
+			case id := <-c.remove:
+				timer.Stop()
+				now = c.now()
+				c.removeEntry(id)
+				c.logger.Info("removed", "entry", id)
+			}
+
+			break
+		}
+	}
+}
+
+// startJob runs the given job in a new goroutine.
+func (c *Cron) startJob(j Job) {
+	c.jobWaiter.Add(1)
+	go func() {
+		defer c.jobWaiter.Done()
+		j.Run()
+	}()
+}
+
+// now returns current time in c location
+func (c *Cron) now() time.Time {
+	return c.clk.Now().In(c.location)
+}
+
+// Stop stops the cron scheduler if it is running; otherwise it does nothing.
+// A context is returned so the caller can wait for running jobs to complete.
+func (c *Cron) Stop() context.Context {
+	c.runningMu.Lock()
+	defer c.runningMu.Unlock()
+	if c.running {
+		c.stop <- struct{}{}
+		c.running = false
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		c.jobWaiter.Wait()
+		cancel()
+	}()
+	return ctx
+}
+
+// entrySnapshot returns a copy of the current cron entry list.
+func (c *Cron) entrySnapshot() []Entry {
+	entries := make([]Entry, len(c.entries))
+	for i, e := range c.entries {
+		entries[i] = *e
+	}
+	return entries
+}
+
+func (c *Cron) removeEntry(id EntryID) {
+	var entries []*Entry
+	for _, e := range c.entries {
+		if e.ID != id {
+			entries = append(entries, e)
+		}
+	}
+	c.entries = entries
+}

cron/cron_test.go

@@ -0,0 +1,739 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/benbjohnson/clock"
+)
+
+// Many tests schedule a job for every second, and then wait at most a second
+// for it to run.  This amount is just slightly larger than 1 second to
+// compensate for a few milliseconds of runtime.
+const OneSecond = 1*time.Second + 50*time.Millisecond
+
+type syncWriter struct {
+	wr bytes.Buffer
+	m  sync.Mutex
+}
+
+func (sw *syncWriter) Write(data []byte) (n int, err error) {
+	sw.m.Lock()
+	n, err = sw.wr.Write(data)
+	sw.m.Unlock()
+	return
+}
+
+func (sw *syncWriter) String() string {
+	sw.m.Lock()
+	defer sw.m.Unlock()
+	return sw.wr.String()
+}
+
+func newBufLogger(sw *syncWriter) Logger {
+	return PrintfLogger(log.New(sw, "", log.LstdFlags))
+}
+
+func TestFuncPanicRecovery(t *testing.T) {
+	var buf syncWriter
+	cron := New(WithParser(secondParser),
+		WithChain(Recover(newBufLogger(&buf))))
+	cron.Start()
+	defer cron.Stop()
+	cron.AddFunc("* * * * * ?", func() {
+		panic("YOLO")
+	})
+
+	select {
+	case <-time.After(OneSecond):
+		if !strings.Contains(buf.String(), "YOLO") {
+			t.Error("expected a panic to be logged, got none")
+		}
+		return
+	}
+}
+
+type DummyJob struct{}
+
+func (d DummyJob) Run() {
+	panic("YOLO")
+}
+
+func TestJobPanicRecovery(t *testing.T) {
+	var job DummyJob
+
+	var buf syncWriter
+	cron := New(WithParser(secondParser),
+		WithChain(Recover(newBufLogger(&buf))))
+	cron.Start()
+	defer cron.Stop()
+	cron.AddJob("* * * * * ?", job)
+
+	select {
+	case <-time.After(OneSecond):
+		if !strings.Contains(buf.String(), "YOLO") {
+			t.Error("expected a panic to be logged, got none")
+		}
+		return
+	}
+}
+
+// Start and stop cron with no entries.
+func TestNoEntries(t *testing.T) {
+	cron := newWithSeconds()
+	cron.Start()
+
+	select {
+	case <-time.After(OneSecond):
+		t.Fatal("expected cron will be stopped immediately")
+	case <-stop(cron):
+	}
+}
+
+// Start, stop, then add an entry. Verify entry doesn't run.
+func TestStopCausesJobsToNotRun(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.Start()
+	cron.Stop()
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+
+	select {
+	case <-time.After(OneSecond):
+		// No job ran!
+	case <-wait(wg):
+		t.Fatal("expected stopped cron does not run any job")
+	}
+}
+
+// Add a job, start cron, expect it runs.
+func TestAddBeforeRunning(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+	cron.Start()
+	defer cron.Stop()
+
+	// Give cron 2 seconds to run our job (which is always activated).
+	select {
+	case <-time.After(OneSecond):
+		t.Fatal("expected job runs")
+	case <-wait(wg):
+	}
+}
+
+// Start cron, add a job, expect it runs.
+func TestAddWhileRunning(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.Start()
+	defer cron.Stop()
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+
+	select {
+	case <-time.After(OneSecond):
+		t.Fatal("expected job runs")
+	case <-wait(wg):
+	}
+}
+
+// Test for #34. Adding a job after calling start results in multiple job invocations
+func TestAddWhileRunningWithDelay(t *testing.T) {
+	cron := newWithSeconds()
+	cron.Start()
+	defer cron.Stop()
+	time.Sleep(5 * time.Second)
+	var calls int64
+	cron.AddFunc("* * * * * *", func() { atomic.AddInt64(&calls, 1) })
+
+	<-time.After(OneSecond)
+	if atomic.LoadInt64(&calls) != 1 {
+		t.Errorf("called %d times, expected 1\n", calls)
+	}
+}
+
+// Add a job, remove a job, start cron, expect nothing runs.
+func TestRemoveBeforeRunning(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	id, _ := cron.AddFunc("* * * * * ?", func() { wg.Done() })
+	cron.Remove(id)
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond):
+		// Success, shouldn't run
+	case <-wait(wg):
+		t.FailNow()
+	}
+}
+
+// Start cron, add a job, remove it, expect it doesn't run.
+func TestRemoveWhileRunning(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.Start()
+	defer cron.Stop()
+	id, _ := cron.AddFunc("* * * * * ?", func() { wg.Done() })
+	cron.Remove(id)
+
+	select {
+	case <-time.After(OneSecond):
+	case <-wait(wg):
+		t.FailNow()
+	}
+}
+
+// Test timing with Entries.
+func TestSnapshotEntries(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := New()
+	cron.AddFunc("@every 2s", func() { wg.Done() })
+	cron.Start()
+	defer cron.Stop()
+
+	// Cron should fire in 2 seconds. After 1 second, call Entries.
+	select {
+	case <-time.After(OneSecond):
+		cron.Entries()
+	}
+
+	// Even though Entries was called, the cron should fire at the 2 second mark.
+	select {
+	case <-time.After(OneSecond):
+		t.Error("expected job runs at 2 second mark")
+	case <-wait(wg):
+	}
+}
+
+// Test that the entries are correctly sorted.
+// Add a bunch of long-in-the-future entries, and an immediate entry, and ensure
+// that the immediate entry runs immediately.
+// Also: Test that multiple jobs run in the same instant.
+func TestMultipleEntries(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(2)
+
+	cron := newWithSeconds()
+	cron.AddFunc("0 0 0 1 1 ?", func() {})
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+	id1, _ := cron.AddFunc("* * * * * ?", func() { t.Fatal() })
+	id2, _ := cron.AddFunc("* * * * * ?", func() { t.Fatal() })
+	cron.AddFunc("0 0 0 31 12 ?", func() {})
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+
+	cron.Remove(id1)
+	cron.Start()
+	cron.Remove(id2)
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond):
+		t.Error("expected job run in proper order")
+	case <-wait(wg):
+	}
+}
+
+// Test running the same job twice.
+func TestRunningJobTwice(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(2)
+
+	cron := newWithSeconds()
+	cron.AddFunc("0 0 0 1 1 ?", func() {})
+	cron.AddFunc("0 0 0 31 12 ?", func() {})
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(2 * OneSecond):
+		t.Error("expected job fires 2 times")
+	case <-wait(wg):
+	}
+}
+
+func TestRunningMultipleSchedules(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(2)
+
+	cron := newWithSeconds()
+	cron.AddFunc("0 0 0 1 1 ?", func() {})
+	cron.AddFunc("0 0 0 31 12 ?", func() {})
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+	cron.Schedule(Every(time.Minute), FuncJob(func() {}))
+	cron.Schedule(Every(time.Second), FuncJob(func() { wg.Done() }))
+	cron.Schedule(Every(time.Hour), FuncJob(func() {}))
+
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(2 * OneSecond):
+		t.Error("expected job fires 2 times")
+	case <-wait(wg):
+	}
+}
+
+// Test that the cron is run in the local time zone (as opposed to UTC).
+func TestLocalTimezone(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(2)
+
+	now := time.Now()
+	// FIX: Issue #205
+	// This calculation doesn't work in seconds 58 or 59.
+	// Take the easy way out and sleep.
+	if now.Second() >= 58 {
+		time.Sleep(2 * time.Second)
+		now = time.Now()
+	}
+	spec := fmt.Sprintf("%d,%d %d %d %d %d ?",
+		now.Second()+1, now.Second()+2, now.Minute(), now.Hour(), now.Day(), now.Month())
+
+	cron := newWithSeconds()
+	cron.AddFunc(spec, func() { wg.Done() })
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond * 2):
+		t.Error("expected job fires 2 times")
+	case <-wait(wg):
+	}
+}
+
+// Test that the cron is run in the given time zone (as opposed to local).
+func TestNonLocalTimezone(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(2)
+
+	loc, err := time.LoadLocation("Atlantic/Cape_Verde")
+	if err != nil {
+		fmt.Printf("Failed to load time zone Atlantic/Cape_Verde: %+v", err)
+		t.Fail()
+	}
+
+	now := time.Now().In(loc)
+	// FIX: Issue #205
+	// This calculation doesn't work in seconds 58 or 59.
+	// Take the easy way out and sleep.
+	if now.Second() >= 58 {
+		time.Sleep(2 * time.Second)
+		now = time.Now().In(loc)
+	}
+	spec := fmt.Sprintf("%d,%d %d %d %d %d ?",
+		now.Second()+1, now.Second()+2, now.Minute(), now.Hour(), now.Day(), now.Month())
+
+	cron := New(WithLocation(loc), WithParser(secondParser))
+	cron.AddFunc(spec, func() { wg.Done() })
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond * 2):
+		t.Error("expected job fires 2 times")
+	case <-wait(wg):
+	}
+}
+
+// Test that calling stop before start silently returns without
+// blocking the stop channel.
+func TestStopWithoutStart(t *testing.T) {
+	cron := New()
+	cron.Stop()
+}
+
+type testJob struct {
+	wg   *sync.WaitGroup
+	name string
+}
+
+func (t testJob) Run() {
+	t.wg.Done()
+}
+
+// Test that adding an invalid job spec returns an error
+func TestInvalidJobSpec(t *testing.T) {
+	cron := New()
+	_, err := cron.AddJob("this will not parse", nil)
+	if err == nil {
+		t.Errorf("expected an error with invalid spec, got nil")
+	}
+}
+
+// Test blocking run method behaves as Start()
+func TestBlockingRun(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.AddFunc("* * * * * ?", func() { wg.Done() })
+
+	unblockChan := make(chan struct{})
+
+	go func() {
+		cron.Run()
+		close(unblockChan)
+	}()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond):
+		t.Error("expected job fires")
+	case <-unblockChan:
+		t.Error("expected that Run() blocks")
+	case <-wait(wg):
+	}
+}
+
+// Test that double-running is a no-op
+func TestStartNoop(t *testing.T) {
+	tickChan := make(chan struct{}, 2)
+
+	cron := newWithSeconds()
+	cron.AddFunc("* * * * * ?", func() {
+		tickChan <- struct{}{}
+	})
+
+	cron.Start()
+	defer cron.Stop()
+
+	// Wait for the first firing to ensure the runner is going
+	<-tickChan
+
+	cron.Start()
+
+	<-tickChan
+
+	// Fail if this job fires again in a short period, indicating a double-run
+	select {
+	case <-time.After(time.Millisecond):
+	case <-tickChan:
+		t.Error("expected job fires exactly twice")
+	}
+}
+
+// Simple test using Runnables.
+func TestJob(t *testing.T) {
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+
+	cron := newWithSeconds()
+	cron.AddJob("0 0 0 30 Feb ?", testJob{wg, "job0"})
+	cron.AddJob("0 0 0 1 1 ?", testJob{wg, "job1"})
+	job2, _ := cron.AddJob("* * * * * ?", testJob{wg, "job2"})
+	cron.AddJob("1 0 0 1 1 ?", testJob{wg, "job3"})
+	cron.Schedule(Every(5*time.Second+5*time.Nanosecond), testJob{wg, "job4"})
+	job5 := cron.Schedule(Every(5*time.Minute), testJob{wg, "job5"})
+
+	// Test getting an Entry pre-Start.
+	if actualName := cron.Entry(job2).Job.(testJob).name; actualName != "job2" {
+		t.Error("wrong job retrieved:", actualName)
+	}
+	if actualName := cron.Entry(job5).Job.(testJob).name; actualName != "job5" {
+		t.Error("wrong job retrieved:", actualName)
+	}
+
+	cron.Start()
+	defer cron.Stop()
+
+	select {
+	case <-time.After(OneSecond):
+		t.FailNow()
+	case <-wait(wg):
+	}
+
+	// Ensure the entries are in the right order.
+	expecteds := []string{"job2", "job4", "job5", "job1", "job3", "job0"}
+
+	var actuals []string
+	for _, entry := range cron.Entries() {
+		actuals = append(actuals, entry.Job.(testJob).name)
+	}
+
+	for i, expected := range expecteds {
+		if actuals[i] != expected {
+			t.Fatalf("Jobs not in the right order.  (expected) %s != %s (actual)", expecteds, actuals)
+		}
+	}
+
+	// Test getting Entries.
+	if actualName := cron.Entry(job2).Job.(testJob).name; actualName != "job2" {
+		t.Error("wrong job retrieved:", actualName)
+	}
+	if actualName := cron.Entry(job5).Job.(testJob).name; actualName != "job5" {
+		t.Error("wrong job retrieved:", actualName)
+	}
+}
+
+// Issue #206
+// Ensure that the next run of a job after removing an entry is accurate.
+func TestScheduleAfterRemoval(t *testing.T) {
+	var wg1 sync.WaitGroup
+	var wg2 sync.WaitGroup
+	wg1.Add(1)
+	wg2.Add(1)
+
+	// The first time this job is run, set a timer and remove the other job
+	// 750ms later. Correct behavior would be to still run the job again in
+	// 250ms, but the bug would cause it to run instead 1s later.
+
+	var calls int
+	var mu sync.Mutex
+
+	cron := newWithSeconds()
+	hourJob := cron.Schedule(Every(time.Hour), FuncJob(func() {}))
+	cron.Schedule(Every(time.Second), FuncJob(func() {
+		mu.Lock()
+		defer mu.Unlock()
+		switch calls {
+		case 0:
+			wg1.Done()
+			calls++
+		case 1:
+			time.Sleep(750 * time.Millisecond)
+			cron.Remove(hourJob)
+			calls++
+		case 2:
+			calls++
+			wg2.Done()
+		case 3:
+			panic("unexpected 3rd call")
+		}
+	}))
+
+	cron.Start()
+	defer cron.Stop()
+
+	// the first run might be any length of time 0 - 1s, since the schedule
+	// rounds to the second. wait for the first run to true up.
+	wg1.Wait()
+
+	select {
+	case <-time.After(2 * OneSecond):
+		t.Error("expected job fires 2 times")
+	case <-wait(&wg2):
+	}
+}
+
+type ZeroSchedule struct{}
+
+func (*ZeroSchedule) Next(time.Time) time.Time {
+	return time.Time{}
+}
+
+// Tests that job without time does not run
+func TestJobWithZeroTimeDoesNotRun(t *testing.T) {
+	cron := newWithSeconds()
+	var calls int64
+	cron.AddFunc("* * * * * *", func() { atomic.AddInt64(&calls, 1) })
+	cron.Schedule(new(ZeroSchedule), FuncJob(func() { t.Error("expected zero task will not run") }))
+	cron.Start()
+	defer cron.Stop()
+	<-time.After(OneSecond)
+	if atomic.LoadInt64(&calls) != 1 {
+		t.Errorf("called %d times, expected 1\n", calls)
+	}
+}
+
+func TestStopAndWait(t *testing.T) {
+	t.Run("nothing running, returns immediately", func(t *testing.T) {
+		cron := newWithSeconds()
+		cron.Start()
+		ctx := cron.Stop()
+		select {
+		case <-ctx.Done():
+		case <-time.After(time.Millisecond):
+			t.Error("context was not done immediately")
+		}
+	})
+
+	t.Run("repeated calls to Stop", func(t *testing.T) {
+		cron := newWithSeconds()
+		cron.Start()
+		_ = cron.Stop()
+		time.Sleep(time.Millisecond)
+		ctx := cron.Stop()
+		select {
+		case <-ctx.Done():
+		case <-time.After(time.Millisecond):
+			t.Error("context was not done immediately")
+		}
+	})
+
+	t.Run("a couple fast jobs added, still returns immediately", func(t *testing.T) {
+		cron := newWithSeconds()
+		cron.AddFunc("* * * * * *", func() {})
+		cron.Start()
+		cron.AddFunc("* * * * * *", func() {})
+		cron.AddFunc("* * * * * *", func() {})
+		cron.AddFunc("* * * * * *", func() {})
+		time.Sleep(time.Second)
+		ctx := cron.Stop()
+		select {
+		case <-ctx.Done():
+		case <-time.After(time.Millisecond):
+			t.Error("context was not done immediately")
+		}
+	})
+
+	t.Run("a couple fast jobs and a slow job added, waits for slow job", func(t *testing.T) {
+		cron := newWithSeconds()
+		cron.AddFunc("* * * * * *", func() {})
+		cron.Start()
+		cron.AddFunc("* * * * * *", func() { time.Sleep(2 * time.Second) })
+		cron.AddFunc("* * * * * *", func() {})
+		time.Sleep(time.Second)
+
+		ctx := cron.Stop()
+
+		// Verify that it is not done for at least 750ms
+		select {
+		case <-ctx.Done():
+			t.Error("context was done too quickly immediately")
+		case <-time.After(750 * time.Millisecond):
+			// expected, because the job sleeping for 1 second is still running
+		}
+
+		// Verify that it IS done in the next 500ms (giving 250ms buffer)
+		select {
+		case <-ctx.Done():
+			// expected
+		case <-time.After(1500 * time.Millisecond):
+			t.Error("context not done after job should have completed")
+		}
+	})
+
+	t.Run("repeated calls to stop, waiting for completion and after", func(t *testing.T) {
+		cron := newWithSeconds()
+		cron.AddFunc("* * * * * *", func() {})
+		cron.AddFunc("* * * * * *", func() { time.Sleep(2 * time.Second) })
+		cron.Start()
+		cron.AddFunc("* * * * * *", func() {})
+		time.Sleep(time.Second)
+		ctx := cron.Stop()
+		ctx2 := cron.Stop()
+
+		// Verify that it is not done for at least 1500ms
+		select {
+		case <-ctx.Done():
+			t.Error("context was done too quickly immediately")
+		case <-ctx2.Done():
+			t.Error("context2 was done too quickly immediately")
+		case <-time.After(1500 * time.Millisecond):
+			// expected, because the job sleeping for 2 seconds is still running
+		}
+
+		// Verify that it IS done in the next 1s (giving 500ms buffer)
+		select {
+		case <-ctx.Done():
+			// expected
+		case <-time.After(time.Second):
+			t.Error("context not done after job should have completed")
+		}
+
+		// Verify that ctx2 is also done.
+		select {
+		case <-ctx2.Done():
+			// expected
+		case <-time.After(time.Millisecond):
+			t.Error("context2 not done even though context1 is")
+		}
+
+		// Verify that a new context retrieved from stop is immediately done.
+		ctx3 := cron.Stop()
+		select {
+		case <-ctx3.Done():
+			// expected
+		case <-time.After(time.Millisecond):
+			t.Error("context not done even when cron Stop is completed")
+		}
+	})
+}
+
+func TestMockClock(t *testing.T) {
+	clk := clock.NewMock()
+	clk.Set(time.Now())
+	cron := New(WithClock(clk))
+	counter := 0
+	cron.AddFunc("@every 1s", func() {
+		counter += 1
+	})
+	cron.Start()
+	defer cron.Stop()
+	for i := 0; i <= 10; i++ {
+		clk.Add(1 * time.Second)
+	}
+	time.Sleep(100 * time.Millisecond)
+	if counter != 10 {
+		t.Errorf("expected 10 calls, got %d", counter)
+	}
+}
+
+func TestMultiThreadedStartAndStop(t *testing.T) {
+	cron := New()
+	go cron.Run()
+	time.Sleep(2 * time.Millisecond)
+	cron.Stop()
+}
+
+func wait(wg *sync.WaitGroup) chan bool {
+	ch := make(chan bool)
+	go func() {
+		wg.Wait()
+		ch <- true
+	}()
+	return ch
+}
+
+func stop(cron *Cron) chan bool {
+	ch := make(chan bool)
+	go func() {
+		cron.Stop()
+		ch <- true
+	}()
+	return ch
+}
+
+// newWithSeconds returns a Cron with the seconds field enabled.
+func newWithSeconds() *Cron {
+	return New(WithParser(secondParser), WithChain())
+}

cron/doc.go

@@ -0,0 +1,243 @@
+//nolint
+/*
+This package is a fork of "github.com/robfig/cron/v3" that implements cron spec parser and job runner with support for mocking the time.
+
+# Usage
+
+Import it in your program as:
+
+	import "github.com/dapr/kit/cron"
+
+It requires Go 1.11 or later due to usage of Go Modules.
+
+# Usage
+
+Callers may register Funcs to be invoked on a given schedule.  Cron will run
+them in their own goroutines.
+
+	c := cron.New()
+	c.AddFunc("30 * * * *", func() { fmt.Println("Every hour on the half hour") })
+	c.AddFunc("30 3-6,20-23 * * *", func() { fmt.Println(".. in the range 3-6am, 8-11pm") })
+	c.AddFunc("CRON_TZ=Asia/Tokyo 30 04 * * *", func() { fmt.Println("Runs at 04:30 Tokyo time every day") })
+	c.AddFunc("@hourly",      func() { fmt.Println("Every hour, starting an hour from now") })
+	c.AddFunc("@every 1h30m", func() { fmt.Println("Every hour thirty, starting an hour thirty from now") })
+	c.Start()
+	..
+	// Funcs are invoked in their own goroutine, asynchronously.
+	...
+	// Funcs may also be added to a running Cron
+	c.AddFunc("@daily", func() { fmt.Println("Every day") })
+	..
+	// Inspect the cron job entries' next and previous run times.
+	inspect(c.Entries())
+	..
+	c.Stop()  // Stop the scheduler (does not stop any jobs already running).
+
+# Time mocking
+
+import "github.com/benbjohnson/clock"
+
+clk := clock.NewMock()
+
+c := cron.New(cron.WithClock(clk))
+
+	c.AddFunc("@every 1h", func() {
+		fmt.Println("Every hour")
+	})
+
+c.Start()
+
+clk.Add(1 * time.Hour)
+
+# CRON Expression Format
+
+A cron expression represents a set of times, using 5 space-separated fields.
+
+	Field name   | Mandatory? | Allowed values  | Allowed special characters
+	----------   | ---------- | --------------  | --------------------------
+	Minutes      | Yes        | 0-59            | * / , -
+	Hours        | Yes        | 0-23            | * / , -
+	Day of month | Yes        | 1-31            | * / , - ?
+	Month        | Yes        | 1-12 or JAN-DEC | * / , -
+	Day of week  | Yes        | 0-6 or SUN-SAT  | * / , - ?
+
+Month and Day-of-week field values are case insensitive.  "SUN", "Sun", and
+"sun" are equally accepted.
+
+The specific interpretation of the format is based on the Cron Wikipedia page:
+https://en.wikipedia.org/wiki/Cron
+
+# Alternative Formats
+
+Alternative Cron expression formats support other fields like seconds. You can
+implement that by creating a custom Parser as follows.
+
+	cron.New(
+		cron.WithParser(
+			cron.NewParser(
+				cron.SecondOptional | cron.Minute | cron.Hour | cron.Dom | cron.Month | cron.Dow | cron.Descriptor)))
+
+Since adding Seconds is the most common modification to the standard cron spec,
+cron provides a builtin function to do that, which is equivalent to the custom
+parser you saw earlier, except that its seconds field is REQUIRED:
+
+	cron.New(cron.WithSeconds())
+
+That emulates Quartz, the most popular alternative Cron schedule format:
+http://www.quartz-scheduler.org/documentation/quartz-2.x/tutorials/crontrigger.html
+
+# Special Characters
+
+Asterisk ( * )
+
+The asterisk indicates that the cron expression will match for all values of the
+field; e.g., using an asterisk in the 5th field (month) would indicate every
+month.
+
+Slash ( / )
+
+Slashes are used to describe increments of ranges. For example 3-59/15 in the
+1st field (minutes) would indicate the 3rd minute of the hour and every 15
+minutes thereafter. The form "*\/..." is equivalent to the form "first-last/...",
+that is, an increment over the largest possible range of the field.  The form
+"N/..." is accepted as meaning "N-MAX/...", that is, starting at N, use the
+increment until the end of that specific range.  It does not wrap around.
+
+Comma ( , )
+
+Commas are used to separate items of a list. For example, using "MON,WED,FRI" in
+the 5th field (day of week) would mean Mondays, Wednesdays and Fridays.
+
+Hyphen ( - )
+
+Hyphens are used to define ranges. For example, 9-17 would indicate every
+hour between 9am and 5pm inclusive.
+
+Question mark ( ? )
+
+Question mark may be used instead of '*' for leaving either day-of-month or
+day-of-week blank.
+
+# Predefined schedules
+
+You may use one of several pre-defined schedules in place of a cron expression.
+
+	Entry                  | Description                                | Equivalent To
+	-----                  | -----------                                | -------------
+	@yearly (or @annually) | Run once a year, midnight, Jan. 1st        | 0 0 1 1 *
+	@monthly               | Run once a month, midnight, first of month | 0 0 1 * *
+	@weekly                | Run once a week, midnight between Sat/Sun  | 0 0 * * 0
+	@daily (or @midnight)  | Run once a day, midnight                   | 0 0 * * *
+	@hourly                | Run once an hour, beginning of hour        | 0 * * * *
+
+# Intervals
+
+You may also schedule a job to execute at fixed intervals, starting at the time it's added
+or cron is run. This is supported by formatting the cron spec like this:
+
+	@every <duration>
+
+where "duration" is a string accepted by time.ParseDuration
+(http://golang.org/pkg/time/#ParseDuration).
+
+For example, "@every 1h30m10s" would indicate a schedule that activates after
+1 hour, 30 minutes, 10 seconds, and then every interval after that.
+
+Note: The interval does not take the job runtime into account.  For example,
+if a job takes 3 minutes to run, and it is scheduled to run every 5 minutes,
+it will have only 2 minutes of idle time between each run.
+
+# Time zones
+
+By default, all interpretation and scheduling is done in the machine's local
+time zone (time.Local). You can specify a different time zone on construction:
+
+	cron.New(
+	    cron.WithLocation(time.UTC))
+
+Individual cron schedules may also override the time zone they are to be
+interpreted in by providing an additional space-separated field at the beginning
+of the cron spec, of the form "CRON_TZ=Asia/Tokyo".
+
+For example:
+
+	# Runs at 6am in time.Local
+	cron.New().AddFunc("0 6 * * ?", ...)
+
+	# Runs at 6am in America/New_York
+	nyc, _ := time.LoadLocation("America/New_York")
+	c := cron.New(cron.WithLocation(nyc))
+	c.AddFunc("0 6 * * ?", ...)
+
+	# Runs at 6am in Asia/Tokyo
+	cron.New().AddFunc("CRON_TZ=Asia/Tokyo 0 6 * * ?", ...)
+
+	# Runs at 6am in Asia/Tokyo
+	c := cron.New(cron.WithLocation(nyc))
+	c.SetLocation("America/New_York")
+	c.AddFunc("CRON_TZ=Asia/Tokyo 0 6 * * ?", ...)
+
+The prefix "TZ=(TIME ZONE)" is also supported for legacy compatibility.
+
+Be aware that jobs scheduled during daylight-savings leap-ahead transitions will
+not be run!
+
+# Job Wrappers
+
+A Cron runner may be configured with a chain of job wrappers to add
+cross-cutting functionality to all submitted jobs. For example, they may be used
+to achieve the following effects:
+
+  - Recover any panics from jobs (activated by default)
+  - Delay a job's execution if the previous run hasn't completed yet
+  - Skip a job's execution if the previous run hasn't completed yet
+  - Log each job's invocations
+
+Install wrappers for all jobs added to a cron using the `cron.WithChain` option:
+
+	cron.New(cron.WithChain(
+		cron.SkipIfStillRunning(logger),
+	))
+
+Install wrappers for individual jobs by explicitly wrapping them:
+
+	job = cron.NewChain(
+		cron.SkipIfStillRunning(logger),
+	).Then(job)
+
+# Thread safety
+
+Since the Cron service runs concurrently with the calling code, some amount of
+care must be taken to ensure proper synchronization.
+
+All cron methods are designed to be correctly synchronized as long as the caller
+ensures that invocations have a clear happens-before ordering between them.
+
+# Logging
+
+Cron defines a Logger interface that is a subset of the one defined in
+github.com/go-logr/logr. It has two logging levels (Info and Error), and
+parameters are key/value pairs. This makes it possible for cron logging to plug
+into structured logging systems. An adapter, [Verbose]PrintfLogger, is provided
+to wrap the standard library *log.Logger.
+
+For additional insight into Cron operations, verbose logging may be activated
+which will record job runs, scheduling decisions, and added or removed jobs.
+Activate it with a one-off logger as follows:
+
+	cron.New(
+		cron.WithLogger(
+			cron.VerbosePrintfLogger(log.New(os.Stdout, "cron: ", log.LstdFlags))))
+
+# Implementation
+
+Cron entries are stored in an array, sorted by their next activation time.  Cron
+sleeps until the next job is due to be run.
+
+Upon waking:
+  - it runs each entry that is active on that second
+  - it calculates the next run times for the jobs that were run
+  - it re-sorts the array of entries by next activation time.
+  - it goes to sleep until the soonest job.
+*/
+package cron

cron/logger.go

@@ -0,0 +1,103 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+	"strings"
+	"time"
+)
+
+// DefaultLogger is used by Cron if none is specified.
+var DefaultLogger Logger = PrintfLogger(log.New(os.Stdout, "cron: ", log.LstdFlags))
+
+// DiscardLogger can be used by callers to discard all log messages.
+var DiscardLogger Logger = PrintfLogger(log.New(ioutil.Discard, "", 0))
+
+// Logger is the interface used in this package for logging, so that any backend
+// can be plugged in. It is a subset of the github.com/go-logr/logr interface.
+type Logger interface {
+	// Info logs routine messages about cron's operation.
+	Info(msg string, keysAndValues ...interface{})
+	// Error logs an error condition.
+	Error(err error, msg string, keysAndValues ...interface{})
+}
+
+// PrintfLogger wraps a Printf-based logger (such as the standard library "log")
+// into an implementation of the Logger interface which logs errors only.
+func PrintfLogger(l interface{ Printf(string, ...interface{}) }) Logger {
+	return printfLogger{l, false}
+}
+
+// VerbosePrintfLogger wraps a Printf-based logger (such as the standard library
+// "log") into an implementation of the Logger interface which logs everything.
+func VerbosePrintfLogger(l interface{ Printf(string, ...interface{}) }) Logger {
+	return printfLogger{l, true}
+}
+
+type printfLogger struct {
+	logger  interface{ Printf(string, ...interface{}) }
+	logInfo bool
+}
+
+func (pl printfLogger) Info(msg string, keysAndValues ...interface{}) {
+	if pl.logInfo {
+		keysAndValues = formatTimes(keysAndValues)
+		pl.logger.Printf(
+			formatString(len(keysAndValues)),
+			append([]interface{}{msg}, keysAndValues...)...)
+	}
+}
+
+func (pl printfLogger) Error(err error, msg string, keysAndValues ...interface{}) {
+	keysAndValues = formatTimes(keysAndValues)
+	pl.logger.Printf(
+		formatString(len(keysAndValues)+2),
+		append([]interface{}{msg, "error", err}, keysAndValues...)...)
+}
+
+// formatString returns a logfmt-like format string for the number of
+// key/values.
+func formatString(numKeysAndValues int) string {
+	var sb strings.Builder
+	sb.WriteString("%s")
+	if numKeysAndValues > 0 {
+		sb.WriteString(", ")
+	}
+	for i := 0; i < numKeysAndValues/2; i++ {
+		if i > 0 {
+			sb.WriteString(", ")
+		}
+		sb.WriteString("%v=%v")
+	}
+	return sb.String()
+}
+
+// formatTimes formats any time.Time values as RFC3339.
+func formatTimes(keysAndValues []interface{}) []interface{} {
+	var formattedArgs []interface{}
+	for _, arg := range keysAndValues {
+		if t, ok := arg.(time.Time); ok {
+			arg = t.Format(time.RFC3339)
+		}
+		formattedArgs = append(formattedArgs, arg)
+	}
+	return formattedArgs
+}

cron/option.go

@@ -0,0 +1,71 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import (
+	"time"
+
+	"github.com/benbjohnson/clock"
+)
+
+// Option represents a modification to the default behavior of a Cron.
+type Option func(*Cron)
+
+// WithLocation overrides the timezone of the cron instance.
+func WithLocation(loc *time.Location) Option {
+	return func(c *Cron) {
+		c.location = loc
+	}
+}
+
+// WithSeconds overrides the parser used for interpreting job schedules to
+// include a seconds field as the first one.
+func WithSeconds() Option {
+	return WithParser(NewParser(
+		Second | Minute | Hour | Dom | Month | Dow | Descriptor,
+	))
+}
+
+// WithParser overrides the parser used for interpreting job schedules.
+func WithParser(p ScheduleParser) Option {
+	return func(c *Cron) {
+		c.parser = p
+	}
+}
+
+// WithChain specifies Job wrappers to apply to all jobs added to this cron.
+// Refer to the Chain* functions in this package for provided wrappers.
+func WithChain(wrappers ...JobWrapper) Option {
+	return func(c *Cron) {
+		c.chain = NewChain(wrappers...)
+	}
+}
+
+// WithLogger uses the provided logger.
+func WithLogger(logger Logger) Option {
+	return func(c *Cron) {
+		c.logger = logger
+	}
+}
+
+// WithClock uses the provided clock to track time.
+func WithClock(clk clock.Clock) Option {
+	return func(c *Cron) {
+		c.clk = clk
+	}
+}

cron/option_test.go

@@ -0,0 +1,59 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import (
+	"log"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestWithLocation(t *testing.T) {
+	c := New(WithLocation(time.UTC))
+	if c.location != time.UTC {
+		t.Errorf("expected UTC, got %v", c.location)
+	}
+}
+
+func TestWithParser(t *testing.T) {
+	parser := NewParser(Dow)
+	c := New(WithParser(parser))
+	if c.parser != parser {
+		t.Error("expected provided parser")
+	}
+}
+
+func TestWithVerboseLogger(t *testing.T) {
+	var buf syncWriter
+	logger := log.New(&buf, "", log.LstdFlags)
+	c := New(WithLogger(VerbosePrintfLogger(logger)))
+	if c.logger.(printfLogger).logger != logger {
+		t.Error("expected provided logger")
+	}
+
+	c.AddFunc("@every 1s", func() {})
+	c.Start()
+	time.Sleep(OneSecond)
+	c.Stop()
+	out := buf.String()
+	if !strings.Contains(out, "schedule,") ||
+		!strings.Contains(out, "run,") {
+		t.Error("expected to see some actions, got:", out)
+	}
+}

cron/parser.go

@@ -0,0 +1,451 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// Configuration options for creating a parser. Most options specify which
+// fields should be included, while others enable features. If a field is not
+// included the parser will assume a default value. These options do not change
+// the order fields are parse in.
+type ParseOption int
+
+const (
+	Second         ParseOption = 1 << iota // Seconds field, default 0
+	SecondOptional                         // Optional seconds field, default 0
+	Minute                                 // Minutes field, default 0
+	Hour                                   // Hours field, default 0
+	Dom                                    // Day of month field, default *
+	Month                                  // Month field, default *
+	Dow                                    // Day of week field, default *
+	DowOptional                            // Optional day of week field, default *
+	Descriptor                             // Allow descriptors such as @monthly, @weekly, etc.
+)
+
+var places = []ParseOption{
+	Second,
+	Minute,
+	Hour,
+	Dom,
+	Month,
+	Dow,
+}
+
+var defaults = []string{
+	"0",
+	"0",
+	"0",
+	"*",
+	"*",
+	"*",
+}
+
+// A custom Parser that can be configured.
+type Parser struct {
+	options ParseOption
+}
+
+// NewParser creates a Parser with custom options.
+//
+// It panics if more than one Optional is given, since it would be impossible to
+// correctly infer which optional is provided or missing in general.
+//
+// Examples
+//
+//	// Standard parser without descriptors
+//	specParser := NewParser(Minute | Hour | Dom | Month | Dow)
+//	sched, err := specParser.Parse("0 0 15 */3 *")
+//
+//	// Same as above, just excludes time fields
+//	specParser := NewParser(Dom | Month | Dow)
+//	sched, err := specParser.Parse("15 */3 *")
+//
+//	// Same as above, just makes Dow optional
+//	specParser := NewParser(Dom | Month | DowOptional)
+//	sched, err := specParser.Parse("15 */3")
+func NewParser(options ParseOption) Parser {
+	optionals := 0
+	if options&DowOptional > 0 {
+		optionals++
+	}
+	if options&SecondOptional > 0 {
+		optionals++
+	}
+	if optionals > 1 {
+		panic("multiple optionals may not be configured")
+	}
+	return Parser{options}
+}
+
+// Parse returns a new crontab schedule representing the given spec.
+// It returns a descriptive error if the spec is not valid.
+// It accepts crontab specs and features configured by NewParser.
+func (p Parser) Parse(spec string) (Schedule, error) {
+	if len(spec) == 0 {
+		return nil, fmt.Errorf("empty spec string")
+	}
+
+	// Extract timezone if present
+	loc := time.Local
+	if strings.HasPrefix(spec, "TZ=") || strings.HasPrefix(spec, "CRON_TZ=") {
+		var err error
+		i := strings.Index(spec, " ")
+		eq := strings.Index(spec, "=")
+		if loc, err = time.LoadLocation(spec[eq+1 : i]); err != nil {
+			return nil, fmt.Errorf("provided bad location %s: %v", spec[eq+1:i], err)
+		}
+		spec = strings.TrimSpace(spec[i:])
+	}
+
+	// Handle named schedules (descriptors), if configured
+	if strings.HasPrefix(spec, "@") {
+		if p.options&Descriptor == 0 {
+			return nil, fmt.Errorf("parser does not accept descriptors: %v", spec)
+		}
+		return parseDescriptor(spec, loc)
+	}
+
+	// Split on whitespace.
+	fields := strings.Fields(spec)
+
+	// Validate & fill in any omitted or optional fields
+	var err error
+	fields, err = normalizeFields(fields, p.options)
+	if err != nil {
+		return nil, err
+	}
+
+	field := func(field string, r bounds) uint64 {
+		if err != nil {
+			return 0
+		}
+		var bits uint64
+		bits, err = getField(field, r)
+		return bits
+	}
+
+	var (
+		second     = field(fields[0], seconds)
+		minute     = field(fields[1], minutes)
+		hour       = field(fields[2], hours)
+		dayofmonth = field(fields[3], dom)
+		month      = field(fields[4], months)
+		dayofweek  = field(fields[5], dow)
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	return &SpecSchedule{
+		Second:   second,
+		Minute:   minute,
+		Hour:     hour,
+		Dom:      dayofmonth,
+		Month:    month,
+		Dow:      dayofweek,
+		Location: loc,
+	}, nil
+}
+
+// normalizeFields takes a subset set of the time fields and returns the full set
+// with defaults (zeroes) populated for unset fields.
+//
+// As part of performing this function, it also validates that the provided
+// fields are compatible with the configured options.
+func normalizeFields(fields []string, options ParseOption) ([]string, error) {
+	// Validate optionals & add their field to options
+	optionals := 0
+	if options&SecondOptional > 0 {
+		options |= Second
+		optionals++
+	}
+	if options&DowOptional > 0 {
+		options |= Dow
+		optionals++
+	}
+	if optionals > 1 {
+		return nil, fmt.Errorf("multiple optionals may not be configured")
+	}
+
+	// Figure out how many fields we need
+	max := 0
+	for _, place := range places {
+		if options&place > 0 {
+			max++
+		}
+	}
+	min := max - optionals
+
+	// Validate number of fields
+	if count := len(fields); count < min || count > max {
+		if min == max {
+			return nil, fmt.Errorf("expected exactly %d fields, found %d: %s", min, count, fields)
+		}
+		return nil, fmt.Errorf("expected %d to %d fields, found %d: %s", min, max, count, fields)
+	}
+
+	// Populate the optional field if not provided
+	if min < max && len(fields) == min {
+		switch {
+		case options&DowOptional > 0:
+			fields = append(fields, defaults[5]) // TODO: improve access to default
+		case options&SecondOptional > 0:
+			fields = append([]string{defaults[0]}, fields...)
+		default:
+			return nil, fmt.Errorf("unknown optional field")
+		}
+	}
+
+	// Populate all fields not part of options with their defaults
+	n := 0
+	expandedFields := make([]string, len(places))
+	copy(expandedFields, defaults)
+	for i, place := range places {
+		if options&place > 0 {
+			expandedFields[i] = fields[n]
+			n++
+		}
+	}
+	return expandedFields, nil
+}
+
+var standardParser = NewParser(
+	Minute | Hour | Dom | Month | Dow | Descriptor,
+)
+
+// ParseStandard returns a new crontab schedule representing the given
+// standardSpec (https://en.wikipedia.org/wiki/Cron). It requires 5 entries
+// representing: minute, hour, day of month, month and day of week, in that
+// order. It returns a descriptive error if the spec is not valid.
+//
+// It accepts
+//   - Standard crontab specs, e.g. "* * * * ?"
+//   - Descriptors, e.g. "@midnight", "@every 1h30m"
+func ParseStandard(standardSpec string) (Schedule, error) {
+	return standardParser.Parse(standardSpec)
+}
+
+// getField returns an Int with the bits set representing all of the times that
+// the field represents or error parsing field value.  A "field" is a comma-separated
+// list of "ranges".
+func getField(field string, r bounds) (uint64, error) {
+	var bits uint64
+	ranges := strings.FieldsFunc(field, func(r rune) bool { return r == ',' })
+	for _, expr := range ranges {
+		bit, err := getRange(expr, r)
+		if err != nil {
+			return bits, err
+		}
+		bits |= bit
+	}
+	return bits, nil
+}
+
+// getRange returns the bits indicated by the given expression:
+//
+//	number | number "-" number [ "/" number ]
+//
+// or error parsing range.
+func getRange(expr string, r bounds) (uint64, error) {
+	var (
+		start, end, step uint
+		rangeAndStep     = strings.Split(expr, "/")
+		lowAndHigh       = strings.Split(rangeAndStep[0], "-")
+		singleDigit      = len(lowAndHigh) == 1
+		err              error
+	)
+
+	var extra uint64
+	if lowAndHigh[0] == "*" || lowAndHigh[0] == "?" {
+		start = r.min
+		end = r.max
+		extra = starBit
+	} else {
+		start, err = parseIntOrName(lowAndHigh[0], r.names)
+		if err != nil {
+			return 0, err
+		}
+		switch len(lowAndHigh) {
+		case 1:
+			end = start
+		case 2:
+			end, err = parseIntOrName(lowAndHigh[1], r.names)
+			if err != nil {
+				return 0, err
+			}
+		default:
+			return 0, fmt.Errorf("too many hyphens: %s", expr)
+		}
+	}
+
+	switch len(rangeAndStep) {
+	case 1:
+		step = 1
+	case 2:
+		step, err = mustParseInt(rangeAndStep[1])
+		if err != nil {
+			return 0, err
+		}
+
+		// Special handling: "N/step" means "N-max/step".
+		if singleDigit {
+			end = r.max
+		}
+		if step > 1 {
+			extra = 0
+		}
+	default:
+		return 0, fmt.Errorf("too many slashes: %s", expr)
+	}
+
+	if start < r.min {
+		return 0, fmt.Errorf("beginning of range (%d) below minimum (%d): %s", start, r.min, expr)
+	}
+	if end > r.max {
+		return 0, fmt.Errorf("end of range (%d) above maximum (%d): %s", end, r.max, expr)
+	}
+	if start > end {
+		return 0, fmt.Errorf("beginning of range (%d) beyond end of range (%d): %s", start, end, expr)
+	}
+	if step == 0 {
+		return 0, fmt.Errorf("step of range should be a positive number: %s", expr)
+	}
+
+	return getBits(start, end, step) | extra, nil
+}
+
+// parseIntOrName returns the (possibly-named) integer contained in expr.
+func parseIntOrName(expr string, names map[string]uint) (uint, error) {
+	if names != nil {
+		if namedInt, ok := names[strings.ToLower(expr)]; ok {
+			return namedInt, nil
+		}
+	}
+	return mustParseInt(expr)
+}
+
+// mustParseInt parses the given expression as an int or returns an error.
+func mustParseInt(expr string) (uint, error) {
+	num, err := strconv.Atoi(expr)
+	if err != nil {
+		return 0, fmt.Errorf("failed to parse int from %s: %s", expr, err)
+	}
+	if num < 0 {
+		return 0, fmt.Errorf("negative number (%d) not allowed: %s", num, expr)
+	}
+
+	return uint(num), nil
+}
+
+// getBits sets all bits in the range [min, max], modulo the given step size.
+func getBits(min, max, step uint) uint64 {
+	var bits uint64
+
+	// If step is 1, use shifts.
+	if step == 1 {
+		return ^(math.MaxUint64 << (max + 1)) & (math.MaxUint64 << min)
+	}
+
+	// Else, use a simple loop.
+	for i := min; i <= max; i += step {
+		bits |= 1 << i
+	}
+	return bits
+}
+
+// all returns all bits within the given bounds.  (plus the star bit)
+func all(r bounds) uint64 {
+	return getBits(r.min, r.max, 1) | starBit
+}
+
+// parseDescriptor returns a predefined schedule for the expression, or error if none matches.
+func parseDescriptor(descriptor string, loc *time.Location) (Schedule, error) {
+	switch descriptor {
+	case "@yearly", "@annually":
+		return &SpecSchedule{
+			Second:   1 << seconds.min,
+			Minute:   1 << minutes.min,
+			Hour:     1 << hours.min,
+			Dom:      1 << dom.min,
+			Month:    1 << months.min,
+			Dow:      all(dow),
+			Location: loc,
+		}, nil
+
+	case "@monthly":
+		return &SpecSchedule{
+			Second:   1 << seconds.min,
+			Minute:   1 << minutes.min,
+			Hour:     1 << hours.min,
+			Dom:      1 << dom.min,
+			Month:    all(months),
+			Dow:      all(dow),
+			Location: loc,
+		}, nil
+
+	case "@weekly":
+		return &SpecSchedule{
+			Second:   1 << seconds.min,
+			Minute:   1 << minutes.min,
+			Hour:     1 << hours.min,
+			Dom:      all(dom),
+			Month:    all(months),
+			Dow:      1 << dow.min,
+			Location: loc,
+		}, nil
+
+	case "@daily", "@midnight":
+		return &SpecSchedule{
+			Second:   1 << seconds.min,
+			Minute:   1 << minutes.min,
+			Hour:     1 << hours.min,
+			Dom:      all(dom),
+			Month:    all(months),
+			Dow:      all(dow),
+			Location: loc,
+		}, nil
+
+	case "@hourly":
+		return &SpecSchedule{
+			Second:   1 << seconds.min,
+			Minute:   1 << minutes.min,
+			Hour:     all(hours),
+			Dom:      all(dom),
+			Month:    all(months),
+			Dow:      all(dow),
+			Location: loc,
+		}, nil
+	}
+
+	const every = "@every "
+	if strings.HasPrefix(descriptor, every) {
+		duration, err := time.ParseDuration(descriptor[len(every):])
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse duration %s: %s", descriptor, err)
+		}
+		return Every(duration), nil
+	}
+
+	return nil, fmt.Errorf("unrecognized descriptor: %s", descriptor)
+}

cron/parser_test.go

@@ -0,0 +1,400 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+var secondParser = NewParser(Second | Minute | Hour | Dom | Month | DowOptional | Descriptor)
+
+func TestRange(t *testing.T) {
+	zero := uint64(0)
+	ranges := []struct {
+		expr     string
+		min, max uint
+		expected uint64
+		err      string
+	}{
+		{"5", 0, 7, 1 << 5, ""},
+		{"0", 0, 7, 1 << 0, ""},
+		{"7", 0, 7, 1 << 7, ""},
+
+		{"5-5", 0, 7, 1 << 5, ""},
+		{"5-6", 0, 7, 1<<5 | 1<<6, ""},
+		{"5-7", 0, 7, 1<<5 | 1<<6 | 1<<7, ""},
+
+		{"5-6/2", 0, 7, 1 << 5, ""},
+		{"5-7/2", 0, 7, 1<<5 | 1<<7, ""},
+		{"5-7/1", 0, 7, 1<<5 | 1<<6 | 1<<7, ""},
+
+		{"*", 1, 3, 1<<1 | 1<<2 | 1<<3 | starBit, ""},
+		{"*/2", 1, 3, 1<<1 | 1<<3, ""},
+
+		{"5--5", 0, 0, zero, "too many hyphens"},
+		{"jan-x", 0, 0, zero, "failed to parse int from"},
+		{"2-x", 1, 5, zero, "failed to parse int from"},
+		{"*/-12", 0, 0, zero, "negative number"},
+		{"*//2", 0, 0, zero, "too many slashes"},
+		{"1", 3, 5, zero, "below minimum"},
+		{"6", 3, 5, zero, "above maximum"},
+		{"5-3", 3, 5, zero, "beyond end of range"},
+		{"*/0", 0, 0, zero, "should be a positive number"},
+	}
+
+	for _, c := range ranges {
+		actual, err := getRange(c.expr, bounds{c.min, c.max, nil})
+		if len(c.err) != 0 && (err == nil || !strings.Contains(err.Error(), c.err)) {
+			t.Errorf("%s => expected %v, got %v", c.expr, c.err, err)
+		}
+		if len(c.err) == 0 && err != nil {
+			t.Errorf("%s => unexpected error %v", c.expr, err)
+		}
+		if actual != c.expected {
+			t.Errorf("%s => expected %d, got %d", c.expr, c.expected, actual)
+		}
+	}
+}
+
+func TestField(t *testing.T) {
+	fields := []struct {
+		expr     string
+		min, max uint
+		expected uint64
+	}{
+		{"5", 1, 7, 1 << 5},
+		{"5,6", 1, 7, 1<<5 | 1<<6},
+		{"5,6,7", 1, 7, 1<<5 | 1<<6 | 1<<7},
+		{"1,5-7/2,3", 1, 7, 1<<1 | 1<<5 | 1<<7 | 1<<3},
+	}
+
+	for _, c := range fields {
+		actual, _ := getField(c.expr, bounds{c.min, c.max, nil})
+		if actual != c.expected {
+			t.Errorf("%s => expected %d, got %d", c.expr, c.expected, actual)
+		}
+	}
+}
+
+func TestAll(t *testing.T) {
+	allBits := []struct {
+		r        bounds
+		expected uint64
+	}{
+		{minutes, 0xfffffffffffffff}, // 0-59: 60 ones
+		{hours, 0xffffff},            // 0-23: 24 ones
+		{dom, 0xfffffffe},            // 1-31: 31 ones, 1 zero
+		{months, 0x1ffe},             // 1-12: 12 ones, 1 zero
+		{dow, 0x7f},                  // 0-6: 7 ones
+	}
+
+	for _, c := range allBits {
+		actual := all(c.r) // all() adds the starBit, so compensate for that..
+		if c.expected|starBit != actual {
+			t.Errorf("%d-%d/%d => expected %b, got %b",
+				c.r.min, c.r.max, 1, c.expected|starBit, actual)
+		}
+	}
+}
+
+func TestBits(t *testing.T) {
+	bits := []struct {
+		min, max, step uint
+		expected       uint64
+	}{
+		{0, 0, 1, 0x1},
+		{1, 1, 1, 0x2},
+		{1, 5, 2, 0x2a}, // 101010
+		{1, 4, 2, 0xa},  // 1010
+	}
+
+	for _, c := range bits {
+		actual := getBits(c.min, c.max, c.step)
+		if c.expected != actual {
+			t.Errorf("%d-%d/%d => expected %b, got %b",
+				c.min, c.max, c.step, c.expected, actual)
+		}
+	}
+}
+
+func TestParseScheduleErrors(t *testing.T) {
+	tests := []struct{ expr, err string }{
+		{"* 5 j * * *", "failed to parse int from"},
+		{"@every Xm", "failed to parse duration"},
+		{"@unrecognized", "unrecognized descriptor"},
+		{"* * * *", "expected 5 to 6 fields"},
+		{"", "empty spec string"},
+	}
+	for _, c := range tests {
+		actual, err := secondParser.Parse(c.expr)
+		if err == nil || !strings.Contains(err.Error(), c.err) {
+			t.Errorf("%s => expected %v, got %v", c.expr, c.err, err)
+		}
+		if actual != nil {
+			t.Errorf("expected nil schedule on error, got %v", actual)
+		}
+	}
+}
+
+func TestParseSchedule(t *testing.T) {
+	tokyo, _ := time.LoadLocation("Asia/Tokyo")
+	entries := []struct {
+		parser   Parser
+		expr     string
+		expected Schedule
+	}{
+		{secondParser, "0 5 * * * *", every5min(time.Local)},
+		{standardParser, "5 * * * *", every5min(time.Local)},
+		{secondParser, "CRON_TZ=UTC  0 5 * * * *", every5min(time.UTC)},
+		{standardParser, "CRON_TZ=UTC  5 * * * *", every5min(time.UTC)},
+		{secondParser, "CRON_TZ=Asia/Tokyo 0 5 * * * *", every5min(tokyo)},
+		{secondParser, "@every 5m", ConstantDelaySchedule{5 * time.Minute}},
+		{secondParser, "@midnight", midnight(time.Local)},
+		{secondParser, "TZ=UTC  @midnight", midnight(time.UTC)},
+		{secondParser, "TZ=Asia/Tokyo @midnight", midnight(tokyo)},
+		{secondParser, "@yearly", annual(time.Local)},
+		{secondParser, "@annually", annual(time.Local)},
+		{
+			parser: secondParser,
+			expr:   "* 5 * * * *",
+			expected: &SpecSchedule{
+				Second:   all(seconds),
+				Minute:   1 << 5,
+				Hour:     all(hours),
+				Dom:      all(dom),
+				Month:    all(months),
+				Dow:      all(dow),
+				Location: time.Local,
+			},
+		},
+	}
+
+	for _, c := range entries {
+		actual, err := c.parser.Parse(c.expr)
+		if err != nil {
+			t.Errorf("%s => unexpected error %v", c.expr, err)
+		}
+		if !reflect.DeepEqual(actual, c.expected) {
+			t.Errorf("%s => expected %b, got %b", c.expr, c.expected, actual)
+		}
+	}
+}
+
+func TestOptionalSecondSchedule(t *testing.T) {
+	parser := NewParser(SecondOptional | Minute | Hour | Dom | Month | Dow | Descriptor)
+	entries := []struct {
+		expr     string
+		expected Schedule
+	}{
+		{"0 5 * * * *", every5min(time.Local)},
+		{"5 5 * * * *", every5min5s(time.Local)},
+		{"5 * * * *", every5min(time.Local)},
+	}
+
+	for _, c := range entries {
+		actual, err := parser.Parse(c.expr)
+		if err != nil {
+			t.Errorf("%s => unexpected error %v", c.expr, err)
+		}
+		if !reflect.DeepEqual(actual, c.expected) {
+			t.Errorf("%s => expected %b, got %b", c.expr, c.expected, actual)
+		}
+	}
+}
+
+func TestNormalizeFields(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    []string
+		options  ParseOption
+		expected []string
+	}{
+		{
+			"AllFields_NoOptional",
+			[]string{"0", "5", "*", "*", "*", "*"},
+			Second | Minute | Hour | Dom | Month | Dow | Descriptor,
+			[]string{"0", "5", "*", "*", "*", "*"},
+		},
+		{
+			"AllFields_SecondOptional_Provided",
+			[]string{"0", "5", "*", "*", "*", "*"},
+			SecondOptional | Minute | Hour | Dom | Month | Dow | Descriptor,
+			[]string{"0", "5", "*", "*", "*", "*"},
+		},
+		{
+			"AllFields_SecondOptional_NotProvided",
+			[]string{"5", "*", "*", "*", "*"},
+			SecondOptional | Minute | Hour | Dom | Month | Dow | Descriptor,
+			[]string{"0", "5", "*", "*", "*", "*"},
+		},
+		{
+			"SubsetFields_NoOptional",
+			[]string{"5", "15", "*"},
+			Hour | Dom | Month,
+			[]string{"0", "0", "5", "15", "*", "*"},
+		},
+		{
+			"SubsetFields_DowOptional_Provided",
+			[]string{"5", "15", "*", "4"},
+			Hour | Dom | Month | DowOptional,
+			[]string{"0", "0", "5", "15", "*", "4"},
+		},
+		{
+			"SubsetFields_DowOptional_NotProvided",
+			[]string{"5", "15", "*"},
+			Hour | Dom | Month | DowOptional,
+			[]string{"0", "0", "5", "15", "*", "*"},
+		},
+		{
+			"SubsetFields_SecondOptional_NotProvided",
+			[]string{"5", "15", "*"},
+			SecondOptional | Hour | Dom | Month,
+			[]string{"0", "0", "5", "15", "*", "*"},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			actual, err := normalizeFields(test.input, test.options)
+			if err != nil {
+				t.Errorf("unexpected error: %v", err)
+			}
+			if !reflect.DeepEqual(actual, test.expected) {
+				t.Errorf("expected %v, got %v", test.expected, actual)
+			}
+		})
+	}
+}
+
+func TestNormalizeFields_Errors(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   []string
+		options ParseOption
+		err     string
+	}{
+		{
+			"TwoOptionals",
+			[]string{"0", "5", "*", "*", "*", "*"},
+			SecondOptional | Minute | Hour | Dom | Month | DowOptional,
+			"",
+		},
+		{
+			"TooManyFields",
+			[]string{"0", "5", "*", "*"},
+			SecondOptional | Minute | Hour,
+			"",
+		},
+		{
+			"NoFields",
+			[]string{},
+			SecondOptional | Minute | Hour,
+			"",
+		},
+		{
+			"TooFewFields",
+			[]string{"*"},
+			SecondOptional | Minute | Hour,
+			"",
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			actual, err := normalizeFields(test.input, test.options)
+			if err == nil {
+				t.Errorf("expected an error, got none. results: %v", actual)
+			}
+			if !strings.Contains(err.Error(), test.err) {
+				t.Errorf("expected error %q, got %q", test.err, err.Error())
+			}
+		})
+	}
+}
+
+func TestStandardSpecSchedule(t *testing.T) {
+	entries := []struct {
+		expr     string
+		expected Schedule
+		err      string
+	}{
+		{
+			expr:     "5 * * * *",
+			expected: &SpecSchedule{1 << seconds.min, 1 << 5, all(hours), all(dom), all(months), all(dow), time.Local},
+		},
+		{
+			expr:     "@every 5m",
+			expected: ConstantDelaySchedule{time.Duration(5) * time.Minute},
+		},
+		{
+			expr: "5 j * * *",
+			err:  "failed to parse int from",
+		},
+		{
+			expr: "* * * *",
+			err:  "expected exactly 5 fields",
+		},
+	}
+
+	for _, c := range entries {
+		actual, err := ParseStandard(c.expr)
+		if len(c.err) != 0 && (err == nil || !strings.Contains(err.Error(), c.err)) {
+			t.Errorf("%s => expected %v, got %v", c.expr, c.err, err)
+		}
+		if len(c.err) == 0 && err != nil {
+			t.Errorf("%s => unexpected error %v", c.expr, err)
+		}
+		if !reflect.DeepEqual(actual, c.expected) {
+			t.Errorf("%s => expected %b, got %b", c.expr, c.expected, actual)
+		}
+	}
+}
+
+func TestNoDescriptorParser(t *testing.T) {
+	parser := NewParser(Minute | Hour)
+	_, err := parser.Parse("@every 1m")
+	if err == nil {
+		t.Error("expected an error, got none")
+	}
+}
+
+func every5min(loc *time.Location) *SpecSchedule {
+	return &SpecSchedule{1 << 0, 1 << 5, all(hours), all(dom), all(months), all(dow), loc}
+}
+
+func every5min5s(loc *time.Location) *SpecSchedule {
+	return &SpecSchedule{1 << 5, 1 << 5, all(hours), all(dom), all(months), all(dow), loc}
+}
+
+func midnight(loc *time.Location) *SpecSchedule {
+	return &SpecSchedule{1, 1, 1, all(dom), all(months), all(dow), loc}
+}
+
+func annual(loc *time.Location) *SpecSchedule {
+	return &SpecSchedule{
+		Second:   1 << seconds.min,
+		Minute:   1 << minutes.min,
+		Hour:     1 << hours.min,
+		Dom:      1 << dom.min,
+		Month:    1 << months.min,
+		Dow:      all(dow),
+		Location: loc,
+	}
+}

cron/spec.go

@@ -0,0 +1,205 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import "time"
+
+// SpecSchedule specifies a duty cycle (to the second granularity), based on a
+// traditional crontab specification. It is computed initially and stored as bit sets.
+type SpecSchedule struct {
+	Second, Minute, Hour, Dom, Month, Dow uint64
+
+	// Override location for this schedule.
+	Location *time.Location
+}
+
+// bounds provides a range of acceptable values (plus a map of name to value).
+type bounds struct {
+	min, max uint
+	names    map[string]uint
+}
+
+// The bounds for each field.
+var (
+	seconds = bounds{0, 59, nil}
+	minutes = bounds{0, 59, nil}
+	hours   = bounds{0, 23, nil}
+	dom     = bounds{1, 31, nil}
+	months  = bounds{1, 12, map[string]uint{
+		"jan": 1,
+		"feb": 2,
+		"mar": 3,
+		"apr": 4,
+		"may": 5,
+		"jun": 6,
+		"jul": 7,
+		"aug": 8,
+		"sep": 9,
+		"oct": 10,
+		"nov": 11,
+		"dec": 12,
+	}}
+	dow = bounds{0, 6, map[string]uint{
+		"sun": 0,
+		"mon": 1,
+		"tue": 2,
+		"wed": 3,
+		"thu": 4,
+		"fri": 5,
+		"sat": 6,
+	}}
+)
+
+const (
+	// Set the top bit if a star was included in the expression.
+	starBit = 1 << 63
+)
+
+// Next returns the next time this schedule is activated, greater than the given
+// time.  If no time can be found to satisfy the schedule, return the zero time.
+func (s *SpecSchedule) Next(t time.Time) time.Time {
+	// General approach
+	//
+	// For Month, Day, Hour, Minute, Second:
+	// Check if the time value matches.  If yes, continue to the next field.
+	// If the field doesn't match the schedule, then increment the field until it matches.
+	// While incrementing the field, a wrap-around brings it back to the beginning
+	// of the field list (since it is necessary to re-verify previous field
+	// values)
+
+	// Convert the given time into the schedule's timezone, if one is specified.
+	// Save the original timezone so we can convert back after we find a time.
+	// Note that schedules without a time zone specified (time.Local) are treated
+	// as local to the time provided.
+	origLocation := t.Location()
+	loc := s.Location
+	if loc == time.Local {
+		loc = t.Location()
+	}
+	if s.Location != time.Local {
+		t = t.In(s.Location)
+	}
+
+	// Start at the earliest possible time (the upcoming second).
+	t = t.Add(1*time.Second - time.Duration(t.Nanosecond())*time.Nanosecond)
+
+	// This flag indicates whether a field has been incremented.
+	added := false
+
+	// If no time is found within five years, return zero.
+	yearLimit := t.Year() + 5
+
+WRAP:
+	if t.Year() > yearLimit {
+		return time.Time{}
+	}
+
+	// Find the first applicable month.
+	// If it's this month, then do nothing.
+	for 1<<uint(t.Month())&s.Month == 0 {
+		// If we have to add a month, reset the other parts to 0.
+		if !added {
+			added = true
+			// Otherwise, set the date at the beginning (since the current time is irrelevant).
+			t = time.Date(t.Year(), t.Month(), 1, 0, 0, 0, 0, loc)
+		}
+		t = t.AddDate(0, 1, 0)
+
+		// Wrapped around.
+		if t.Month() == time.January {
+			goto WRAP
+		}
+	}
+
+	// Now get a day in that month.
+	//
+	// NOTE: This causes issues for daylight savings regimes where midnight does
+	// not exist.  For example: Sao Paulo has DST that transforms midnight on
+	// 11/3 into 1am. Handle that by noticing when the Hour ends up != 0.
+	for !dayMatches(s, t) {
+		if !added {
+			added = true
+			t = time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, loc)
+		}
+		t = t.AddDate(0, 0, 1)
+		// Notice if the hour is no longer midnight due to DST.
+		// Add an hour if it's 23, subtract an hour if it's 1.
+		if t.Hour() != 0 {
+			if t.Hour() > 12 {
+				t = t.Add(time.Duration(24-t.Hour()) * time.Hour)
+			} else {
+				t = t.Add(time.Duration(-t.Hour()) * time.Hour)
+			}
+		}
+
+		if t.Day() == 1 {
+			goto WRAP
+		}
+	}
+
+	for 1<<uint(t.Hour())&s.Hour == 0 {
+		if !added {
+			added = true
+			t = time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), 0, 0, 0, loc)
+		}
+		t = t.Add(1 * time.Hour)
+
+		if t.Hour() == 0 {
+			goto WRAP
+		}
+	}
+
+	for 1<<uint(t.Minute())&s.Minute == 0 {
+		if !added {
+			added = true
+			t = t.Truncate(time.Minute)
+		}
+		t = t.Add(1 * time.Minute)
+
+		if t.Minute() == 0 {
+			goto WRAP
+		}
+	}
+
+	for 1<<uint(t.Second())&s.Second == 0 {
+		if !added {
+			added = true
+			t = t.Truncate(time.Second)
+		}
+		t = t.Add(1 * time.Second)
+
+		if t.Second() == 0 {
+			goto WRAP
+		}
+	}
+
+	return t.In(origLocation)
+}
+
+// dayMatches returns true if the schedule's day-of-week and day-of-month
+// restrictions are satisfied by the given time.
+func dayMatches(s *SpecSchedule, t time.Time) bool {
+	var (
+		domMatch bool = 1<<uint(t.Day())&s.Dom > 0
+		dowMatch bool = 1<<uint(t.Weekday())&s.Dow > 0
+	)
+	if s.Dom&starBit > 0 || s.Dow&starBit > 0 {
+		return domMatch && dowMatch
+	}
+	return domMatch || dowMatch
+}

cron/spec_test.go

@@ -0,0 +1,317 @@
+/*
+Copyright 2022 The Dapr Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+This package has been forked from https://github.com/robfig/cron available under the MIT license.
+You can check the original license at:
+		https://github.com/robfig/cron/blob/master/LICENSE
+*/
+
+//nolint
+package cron
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestActivation(t *testing.T) {
+	tests := []struct {
+		time, spec string
+		expected   bool
+	}{
+		// Every fifteen minutes.
+		{"Mon Jul 9 15:00 2012", "0/15 * * * *", true},
+		{"Mon Jul 9 15:45 2012", "0/15 * * * *", true},
+		{"Mon Jul 9 15:40 2012", "0/15 * * * *", false},
+
+		// Every fifteen minutes, starting at 5 minutes.
+		{"Mon Jul 9 15:05 2012", "5/15 * * * *", true},
+		{"Mon Jul 9 15:20 2012", "5/15 * * * *", true},
+		{"Mon Jul 9 15:50 2012", "5/15 * * * *", true},
+
+		// Named months
+		{"Sun Jul 15 15:00 2012", "0/15 * * Jul *", true},
+		{"Sun Jul 15 15:00 2012", "0/15 * * Jun *", false},
+
+		// Everything set.
+		{"Sun Jul 15 08:30 2012", "30 08 ? Jul Sun", true},
+		{"Sun Jul 15 08:30 2012", "30 08 15 Jul ?", true},
+		{"Mon Jul 16 08:30 2012", "30 08 ? Jul Sun", false},
+		{"Mon Jul 16 08:30 2012", "30 08 15 Jul ?", false},
+
+		// Predefined schedules
+		{"Mon Jul 9 15:00 2012", "@hourly", true},
+		{"Mon Jul 9 15:04 2012", "@hourly", false},
+		{"Mon Jul 9 15:00 2012", "@daily", false},
+		{"Mon Jul 9 00:00 2012", "@daily", true},
+		{"Mon Jul 9 00:00 2012", "@weekly", false},
+		{"Sun Jul 8 00:00 2012", "@weekly", true},
+		{"Sun Jul 8 01:00 2012", "@weekly", false},
+		{"Sun Jul 8 00:00 2012", "@monthly", false},
+		{"Sun Jul 1 00:00 2012", "@monthly", true},
+
+		// Test interaction of DOW and DOM.
+		// If both are restricted, then only one needs to match.
+		{"Sun Jul 15 00:00 2012", "* * 1,15 * Sun", true},
+		{"Fri Jun 15 00:00 2012", "* * 1,15 * Sun", true},
+		{"Wed Aug 1 00:00 2012", "* * 1,15 * Sun", true},
+		{"Sun Jul 15 00:00 2012", "* * */10 * Sun", true}, // verifies #70
+
+		// However, if one has a star, then both need to match.
+		{"Sun Jul 15 00:00 2012", "* * * * Mon", false},
+		{"Mon Jul 9 00:00 2012", "* * 1,15 * *", false},
+		{"Sun Jul 15 00:00 2012", "* * 1,15 * *", true},
+		{"Sun Jul 15 00:00 2012", "* * */2 * Sun", true},
+	}
+
+	for _, test := range tests {
+		sched, err := ParseStandard(test.spec)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		actual := sched.Next(getTime(test.time).Add(-1 * time.Second))
+		expected := getTime(test.time)
+		if test.expected && expected != actual || !test.expected && expected == actual {
+			t.Errorf("Fail evaluating %s on %s: (expected) %s != %s (actual)",
+				test.spec, test.time, expected, actual)
+		}
+	}
+}
+
+func TestNext(t *testing.T) {
+	runs := []struct {
+		time, spec string
+		expected   string
+	}{
+		// Simple cases
+		{"Mon Jul 9 14:45 2012", "0 0/15 * * * *", "Mon Jul 9 15:00 2012"},
+		{"Mon Jul 9 14:59 2012", "0 0/15 * * * *", "Mon Jul 9 15:00 2012"},
+		{"Mon Jul 9 14:59:59 2012", "0 0/15 * * * *", "Mon Jul 9 15:00 2012"},
+
+		// Wrap around hours
+		{"Mon Jul 9 15:45 2012", "0 20-35/15 * * * *", "Mon Jul 9 16:20 2012"},
+
+		// Wrap around days
+		{"Mon Jul 9 23:46 2012", "0 */15 * * * *", "Tue Jul 10 00:00 2012"},
+		{"Mon Jul 9 23:45 2012", "0 20-35/15 * * * *", "Tue Jul 10 00:20 2012"},
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 * * * *", "Tue Jul 10 00:20:15 2012"},
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 1/2 * * *", "Tue Jul 10 01:20:15 2012"},
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 10-12 * * *", "Tue Jul 10 10:20:15 2012"},
+
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 1/2 */2 * *", "Thu Jul 11 01:20:15 2012"},
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 * 9-20 * *", "Wed Jul 10 00:20:15 2012"},
+		{"Mon Jul 9 23:35:51 2012", "15/35 20-35/15 * 9-20 Jul *", "Wed Jul 10 00:20:15 2012"},
+
+		// Wrap around months
+		{"Mon Jul 9 23:35 2012", "0 0 0 9 Apr-Oct ?", "Thu Aug 9 00:00 2012"},
+		{"Mon Jul 9 23:35 2012", "0 0 0 */5 Apr,Aug,Oct Mon", "Tue Aug 1 00:00 2012"},
+		{"Mon Jul 9 23:35 2012", "0 0 0 */5 Oct Mon", "Mon Oct 1 00:00 2012"},
+
+		// Wrap around years
+		{"Mon Jul 9 23:35 2012", "0 0 0 * Feb Mon", "Mon Feb 4 00:00 2013"},
+		{"Mon Jul 9 23:35 2012", "0 0 0 * Feb Mon/2", "Fri Feb 1 00:00 2013"},
+
+		// Wrap around minute, hour, day, month, and year
+		{"Mon Dec 31 23:59:45 2012", "0 * * * * *", "Tue Jan 1 00:00:00 2013"},
+
+		// Leap year
+		{"Mon Jul 9 23:35 2012", "0 0 0 29 Feb ?", "Mon Feb 29 00:00 2016"},
+
+		// Daylight savings time 2am EST (-5) -> 3am EDT (-4)
+		{"2012-03-11T00:00:00-0500", "TZ=America/New_York 0 30 2 11 Mar ?", "2013-03-11T02:30:00-0400"},
+
+		// hourly job
+		{"2012-03-11T00:00:00-0500", "TZ=America/New_York 0 0 * * * ?", "2012-03-11T01:00:00-0500"},
+		{"2012-03-11T01:00:00-0500", "TZ=America/New_York 0 0 * * * ?", "2012-03-11T03:00:00-0400"},
+		{"2012-03-11T03:00:00-0400", "TZ=America/New_York 0 0 * * * ?", "2012-03-11T04:00:00-0400"},
+		{"2012-03-11T04:00:00-0400", "TZ=America/New_York 0 0 * * * ?", "2012-03-11T05:00:00-0400"},
+
+		// hourly job using CRON_TZ
+		{"2012-03-11T00:00:00-0500", "CRON_TZ=America/New_York 0 0 * * * ?", "2012-03-11T01:00:00-0500"},
+		{"2012-03-11T01:00:00-0500", "CRON_TZ=America/New_York 0 0 * * * ?", "2012-03-11T03:00:00-0400"},
+		{"2012-03-11T03:00:00-0400", "CRON_TZ=America/New_York 0 0 * * * ?", "2012-03-11T04:00:00-0400"},
+		{"2012-03-11T04:00:00-0400", "CRON_TZ=America/New_York 0 0 * * * ?", "2012-03-11T05:00:00-0400"},
+
+		// 1am nightly job
+		{"2012-03-11T00:00:00-0500", "TZ=America/New_York 0 0 1 * * ?", "2012-03-11T01:00:00-0500"},
+		{"2012-03-11T01:00:00-0500", "TZ=America/New_York 0 0 1 * * ?", "2012-03-12T01:00:00-0400"},
+
+		// 2am nightly job (skipped)
+		{"2012-03-11T00:00:00-0500", "TZ=America/New_York 0 0 2 * * ?", "2012-03-12T02:00:00-0400"},
+
+		// Daylight savings time 2am EDT (-4) => 1am EST (-5)
+		{"2012-11-04T00:00:00-0400", "TZ=America/New_York 0 30 2 04 Nov ?", "2012-11-04T02:30:00-0500"},
+		{"2012-11-04T01:45:00-0400", "TZ=America/New_York 0 30 1 04 Nov ?", "2012-11-04T01:30:00-0500"},
+
+		// hourly job
+		{"2012-11-04T00:00:00-0400", "TZ=America/New_York 0 0 * * * ?", "2012-11-04T01:00:00-0400"},
+		{"2012-11-04T01:00:00-0400", "TZ=America/New_York 0 0 * * * ?", "2012-11-04T01:00:00-0500"},
+		{"2012-11-04T01:00:00-0500", "TZ=America/New_York 0 0 * * * ?", "2012-11-04T02:00:00-0500"},
+
+		// 1am nightly job (runs twice)
+		{"2012-11-04T00:00:00-0400", "TZ=America/New_York 0 0 1 * * ?", "2012-11-04T01:00:00-0400"},
+		{"2012-11-04T01:00:00-0400", "TZ=America/New_York 0 0 1 * * ?", "2012-11-04T01:00:00-0500"},
+		{"2012-11-04T01:00:00-0500", "TZ=America/New_York 0 0 1 * * ?", "2012-11-05T01:00:00-0500"},
+
+		// 2am nightly job
+		{"2012-11-04T00:00:00-0400", "TZ=America/New_York 0 0 2 * * ?", "2012-11-04T02:00:00-0500"},
+		{"2012-11-04T02:00:00-0500", "TZ=America/New_York 0 0 2 * * ?", "2012-11-05T02:00:00-0500"},
+
+		// 3am nightly job
+		{"2012-11-04T00:00:00-0400", "TZ=America/New_York 0 0 3 * * ?", "2012-11-04T03:00:00-0500"},
+		{"2012-11-04T03:00:00-0500", "TZ=America/New_York 0 0 3 * * ?", "2012-11-05T03:00:00-0500"},
+
+		// hourly job
+		{"TZ=America/New_York 2012-11-04T00:00:00-0400", "0 0 * * * ?", "2012-11-04T01:00:00-0400"},
+		{"TZ=America/New_York 2012-11-04T01:00:00-0400", "0 0 * * * ?", "2012-11-04T01:00:00-0500"},
+		{"TZ=America/New_York 2012-11-04T01:00:00-0500", "0 0 * * * ?", "2012-11-04T02:00:00-0500"},
+
+		// 1am nightly job (runs twice)
+		{"TZ=America/New_York 2012-11-04T00:00:00-0400", "0 0 1 * * ?", "2012-11-04T01:00:00-0400"},
+		{"TZ=America/New_York 2012-11-04T01:00:00-0400", "0 0 1 * * ?", "2012-11-04T01:00:00-0500"},
+		{"TZ=America/New_York 2012-11-04T01:00:00-0500", "0 0 1 * * ?", "2012-11-05T01:00:00-0500"},
+
+		// 2am nightly job
+		{"TZ=America/New_York 2012-11-04T00:00:00-0400", "0 0 2 * * ?", "2012-11-04T02:00:00-0500"},
+		{"TZ=America/New_York 2012-11-04T02:00:00-0500", "0 0 2 * * ?", "2012-11-05T02:00:00-0500"},
+
+		// 3am nightly job
+		{"TZ=America/New_York 2012-11-04T00:00:00-0400", "0 0 3 * * ?", "2012-11-04T03:00:00-0500"},
+		{"TZ=America/New_York 2012-11-04T03:00:00-0500", "0 0 3 * * ?", "2012-11-05T03:00:00-0500"},
+
+		// Unsatisfiable
+		{"Mon Jul 9 23:35 2012", "0 0 0 30 Feb ?", ""},
+		{"Mon Jul 9 23:35 2012", "0 0 0 31 Apr ?", ""},
+
+		// Monthly job
+		{"TZ=America/New_York 2012-11-04T00:00:00-0400", "0 0 3 3 * ?", "2012-12-03T03:00:00-0500"},
+
+		// Test the scenario of DST resulting in midnight not being a valid time.
+		// https://github.com/robfig/cron/issues/157
+		{"2018-10-17T05:00:00-0400", "TZ=America/Sao_Paulo 0 0 9 10 * ?", "2018-11-10T06:00:00-0500"},
+		{"2018-02-14T05:00:00-0500", "TZ=America/Sao_Paulo 0 0 9 22 * ?", "2018-02-22T07:00:00-0500"},
+	}
+
+	for _, c := range runs {
+		sched, err := secondParser.Parse(c.spec)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		actual := sched.Next(getTime(c.time))
+		expected := getTime(c.expected)
+		if !actual.Equal(expected) {
+			t.Errorf("%s, \"%s\": (expected) %v != %v (actual)", c.time, c.spec, expected, actual)
+		}
+	}
+}
+
+func TestErrors(t *testing.T) {
+	invalidSpecs := []string{
+		"xyz",
+		"60 0 * * *",
+		"0 60 * * *",
+		"0 0 * * XYZ",
+	}
+	for _, spec := range invalidSpecs {
+		_, err := ParseStandard(spec)
+		if err == nil {
+			t.Error("expected an error parsing: ", spec)
+		}
+	}
+}
+
+func getTime(value string) time.Time {
+	if value == "" {
+		return time.Time{}
+	}
+
+	location := time.Local
+	if strings.HasPrefix(value, "TZ=") {
+		parts := strings.Fields(value)
+		loc, err := time.LoadLocation(parts[0][len("TZ="):])
+		if err != nil {
+			panic("could not parse location:" + err.Error())
+		}
+		location = loc
+		value = parts[1]
+	}
+
+	layouts := []string{
+		"Mon Jan 2 15:04 2006",
+		"Mon Jan 2 15:04:05 2006",
+	}
+	for _, layout := range layouts {
+		if t, err := time.ParseInLocation(layout, value, location); err == nil {
+			return t
+		}
+	}
+	if t, err := time.ParseInLocation("2006-01-02T15:04:05-0700", value, location); err == nil {
+		return t
+	}
+	panic("could not parse time value " + value)
+}
+
+func TestNextWithTz(t *testing.T) {
+	runs := []struct {
+		time, spec string
+		expected   string
+	}{
+		// Failing tests
+		{"2016-01-03T13:09:03+0530", "14 14 * * *", "2016-01-03T14:14:00+0530"},
+		{"2016-01-03T04:09:03+0530", "14 14 * * ?", "2016-01-03T14:14:00+0530"},
+
+		// Passing tests
+		{"2016-01-03T14:09:03+0530", "14 14 * * *", "2016-01-03T14:14:00+0530"},
+		{"2016-01-03T14:00:00+0530", "14 14 * * ?", "2016-01-03T14:14:00+0530"},
+	}
+	for _, c := range runs {
+		sched, err := ParseStandard(c.spec)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		actual := sched.Next(getTimeTZ(c.time))
+		expected := getTimeTZ(c.expected)
+		if !actual.Equal(expected) {
+			t.Errorf("%s, \"%s\": (expected) %v != %v (actual)", c.time, c.spec, expected, actual)
+		}
+	}
+}
+
+func getTimeTZ(value string) time.Time {
+	if value == "" {
+		return time.Time{}
+	}
+	t, err := time.Parse("Mon Jan 2 15:04 2006", value)
+	if err != nil {
+		t, err = time.Parse("Mon Jan 2 15:04:05 2006", value)
+		if err != nil {
+			t, err = time.Parse("2006-01-02T15:04:05-0700", value)
+			if err != nil {
+				panic(err)
+			}
+		}
+	}
+
+	return t
+}
+
+// https://github.com/robfig/cron/issues/144
+func TestSlash0NoHang(t *testing.T) {
+	schedule := "TZ=America/New_York 15/0 * * * *"
+	_, err := ParseStandard(schedule)
+	if err == nil {
+		t.Error("expected an error on 0 increment")
+	}
+}

go.mod

@@ -3,6 +3,7 @@ module github.com/dapr/kit
 go 1.19
 
 require (
+	github.com/benbjohnson/clock v1.3.0
 	github.com/cenkalti/backoff/v4 v4.2.0
 	github.com/fsnotify/fsnotify v1.6.0
 	github.com/mitchellh/mapstructure v1.5.1-0.20220423185008-bf980b35cac4

go.sum

@@ -1,3 +1,5 @@
+github.com/benbjohnson/clock v1.3.0 h1:ip6w0uFQkncKQ979AypyG0ER7mqUSBdKLOgAle/AT8A=
+github.com/benbjohnson/clock v1.3.0/go.mod h1:J11/hYXuz8f4ySSvYwY0FKfm+ezbsZBKZxNJlLklBHA=
 github.com/cenkalti/backoff/v4 v4.2.0 h1:HN5dHm3WBOgndBH6E8V0q2jIYIR3s9yglV8k/+MN3u4=
 github.com/cenkalti/backoff/v4 v4.2.0/go.mod h1:Y3VNntkOUPxTVeUxJ/G5vcM//AlwfmyYozVcomhLiZE=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=