Refactor protokube hosts file into its own package

So we can bring this in without our gossip layer

This supports an imminent implementation that uses DNS-SD

hack/.packages

@@ -102,6 +102,7 @@ k8s.io/kops/protokube/pkg/etcd
 k8s.io/kops/protokube/pkg/gossip
 k8s.io/kops/protokube/pkg/gossip/aws
 k8s.io/kops/protokube/pkg/gossip/dns
+k8s.io/kops/protokube/pkg/gossip/dns/hosts
 k8s.io/kops/protokube/pkg/gossip/dns/provider
 k8s.io/kops/protokube/pkg/gossip/gce
 k8s.io/kops/protokube/pkg/gossip/mesh

protokube/pkg/gossip/dns/BUILD.bazel

@@ -10,6 +10,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//protokube/pkg/gossip:go_default_library",
+        "//protokube/pkg/gossip/dns/hosts:go_default_library",
         "//vendor/github.com/golang/glog:go_default_library",
     ],
 )

protokube/pkg/gossip/dns/hosts.go

@@ -17,19 +17,10 @@ limitations under the License.
 package dns
 
 import (
-	"fmt"
-	"io/ioutil"
-	"os"
-	"path/filepath"
-	"sort"
-	"strings"
-
 	"github.com/golang/glog"
+	"k8s.io/kops/protokube/pkg/gossip/dns/hosts"
 )
 
-const GUARD_BEGIN = "# Begin host entries managed by kops - do not edit"
-const GUARD_END = "# End host entries managed by kops"
-
 // HostsFile stores DNS records into /etc/hosts
 type HostsFile struct {
 	Path string
@@ -58,109 +49,5 @@ func (h *HostsFile) Update(snapshot *DNSViewSnapshot) error {
 		}
 	}
 
-	stat, err := os.Stat(h.Path)
-	if err != nil {
-		return fmt.Errorf("error getting file status of %q: %v", h.Path, err)
-	}
-
-	data, err := ioutil.ReadFile(h.Path)
-	if err != nil {
-		return fmt.Errorf("error reading file %q: %v", h.Path, err)
-	}
-
-	var out []string
-	depth := 0
-	for _, line := range strings.Split(string(data), "\n") {
-		k := strings.TrimSpace(line)
-		if k == GUARD_BEGIN {
-			depth++
-		}
-
-		if depth <= 0 {
-			out = append(out, line)
-		}
-
-		if k == GUARD_END {
-			depth--
-		}
-	}
-
-	// Ensure a single blank line
-	for {
-		if len(out) == 0 {
-			break
-		}
-
-		if out[len(out)-1] != "" {
-			break
-		}
-
-		out = out[:len(out)-1]
-	}
-	out = append(out, "")
-
-	out = append(out, GUARD_BEGIN)
-	for addr, hosts := range addrToHosts {
-		sort.Strings(hosts)
-		out = append(out, addr+"\t"+strings.Join(hosts, " "))
-	}
-	out = append(out, GUARD_END)
-	out = append(out, "")
-
-	// Note that because we are bind mounting /etc/hosts, we can't do a normal atomic file write
-	// (where we write a temp file and rename it)
-	// TODO: We should just hold the file open while we read & write it
-	err = ioutil.WriteFile(h.Path, []byte(strings.Join(out, "\n")), stat.Mode().Perm())
-	if err != nil {
-		return fmt.Errorf("error writing file %q: %v", h.Path, err)
-	}
-
-	return nil
-}
-
-func atomicWriteFile(filename string, data []byte, perm os.FileMode) error {
-	dir := filepath.Dir(filename)
-
-	tempFile, err := ioutil.TempFile(dir, ".tmp"+filepath.Base(filename))
-	if err != nil {
-		return fmt.Errorf("error creating temp file in %q: %v", dir, err)
-	}
-
-	mustClose := true
-	mustRemove := true
-
-	defer func() {
-		if mustClose {
-			if err := tempFile.Close(); err != nil {
-				glog.Warningf("error closing temp file: %v", err)
-			}
-		}
-
-		if mustRemove {
-			if err := os.Remove(tempFile.Name()); err != nil {
-				glog.Warningf("error removing temp file %q: %v", tempFile.Name(), err)
-			}
-		}
-	}()
-
-	if _, err := tempFile.Write(data); err != nil {
-		return fmt.Errorf("error writing temp file: %v", err)
-	}
-
-	if err := tempFile.Close(); err != nil {
-		return fmt.Errorf("error closing temp file: %v", err)
-	}
-
-	mustClose = false
-
-	if err := os.Chmod(tempFile.Name(), perm); err != nil {
-		return fmt.Errorf("error changing mode of temp file: %v", err)
-	}
-
-	if err := os.Rename(tempFile.Name(), filename); err != nil {
-		return fmt.Errorf("error moving temp file %q to %q: %v", tempFile.Name(), filename, err)
-	}
-
-	mustRemove = false
-	return nil
+	return hosts.UpdateHostsFileWithRecords(h.Path, addrToHosts)
 }

protokube/pkg/gossip/dns/hosts/BUILD.bazel

@@ -0,0 +1,9 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["hosts.go"],
+    importpath = "k8s.io/kops/protokube/pkg/gossip/dns/hosts",
+    visibility = ["//visibility:public"],
+    deps = ["//vendor/github.com/golang/glog:go_default_library"],
+)

protokube/pkg/gossip/dns/hosts/hosts.go

@@ -0,0 +1,139 @@
+/*
+Copyright 2017 The Kubernetes 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.
+*/
+
+package hosts
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+
+	"github.com/golang/glog"
+)
+
+const GUARD_BEGIN = "# Begin host entries managed by kops - do not edit"
+const GUARD_END = "# End host entries managed by kops"
+
+func UpdateHostsFileWithRecords(p string, addrToHosts map[string][]string) error {
+	stat, err := os.Stat(p)
+	if err != nil {
+		return fmt.Errorf("error getting file status of %q: %v", p, err)
+	}
+
+	data, err := ioutil.ReadFile(p)
+	if err != nil {
+		return fmt.Errorf("error reading file %q: %v", p, err)
+	}
+
+	var out []string
+	depth := 0
+	for _, line := range strings.Split(string(data), "\n") {
+		k := strings.TrimSpace(line)
+		if k == GUARD_BEGIN {
+			depth++
+		}
+
+		if depth <= 0 {
+			out = append(out, line)
+		}
+
+		if k == GUARD_END {
+			depth--
+		}
+	}
+
+	// Ensure a single blank line
+	for {
+		if len(out) == 0 {
+			break
+		}
+
+		if out[len(out)-1] != "" {
+			break
+		}
+
+		out = out[:len(out)-1]
+	}
+	out = append(out, "")
+
+	out = append(out, GUARD_BEGIN)
+	for addr, hosts := range addrToHosts {
+		sort.Strings(hosts)
+		out = append(out, addr+"\t"+strings.Join(hosts, " "))
+	}
+	out = append(out, GUARD_END)
+	out = append(out, "")
+
+	// Note that because we are bind mounting /etc/hosts, we can't do a normal atomic file write
+	// (where we write a temp file and rename it)
+	// TODO: We should just hold the file open while we read & write it
+	err = ioutil.WriteFile(p, []byte(strings.Join(out, "\n")), stat.Mode().Perm())
+	if err != nil {
+		return fmt.Errorf("error writing file %q: %v", p, err)
+	}
+
+	return nil
+}
+
+func atomicWriteFile(filename string, data []byte, perm os.FileMode) error {
+	dir := filepath.Dir(filename)
+
+	tempFile, err := ioutil.TempFile(dir, ".tmp"+filepath.Base(filename))
+	if err != nil {
+		return fmt.Errorf("error creating temp file in %q: %v", dir, err)
+	}
+
+	mustClose := true
+	mustRemove := true
+
+	defer func() {
+		if mustClose {
+			if err := tempFile.Close(); err != nil {
+				glog.Warningf("error closing temp file: %v", err)
+			}
+		}
+
+		if mustRemove {
+			if err := os.Remove(tempFile.Name()); err != nil {
+				glog.Warningf("error removing temp file %q: %v", tempFile.Name(), err)
+			}
+		}
+	}()
+
+	if _, err := tempFile.Write(data); err != nil {
+		return fmt.Errorf("error writing temp file: %v", err)
+	}
+
+	if err := tempFile.Close(); err != nil {
+		return fmt.Errorf("error closing temp file: %v", err)
+	}
+
+	mustClose = false
+
+	if err := os.Chmod(tempFile.Name(), perm); err != nil {
+		return fmt.Errorf("error changing mode of temp file: %v", err)
+	}
+
+	if err := os.Rename(tempFile.Name(), filename); err != nil {
+		return fmt.Errorf("error moving temp file %q to %q: %v", tempFile.Name(), filename, err)
+	}
+
+	mustRemove = false
+	return nil
+}