Add the commit ID key as constant for log label (#158)

* add the commit id constant

* add changeset lib

* add doc.go with explanation

changeset/commit.go

@@ -0,0 +1,64 @@
+/*
+Copyright 2018 The Knative 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 changeset
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+const (
+	commitIDFile      = "HEAD"
+	koDataPathEnvName = "KO_DATA_PATH"
+)
+
+var (
+	commitIDRE = regexp.MustCompile(`^[a-f0-9]{40}$`)
+)
+
+// Get tries to fetch the first 7 digitals of GitHub commit ID from HEAD file in
+// KO_DATA_PATH. If it fails, it returns the error it gets.
+func Get() (string, error) {
+	data, err := readFileFromKoData(commitIDFile)
+	if err != nil {
+		return "", err
+	}
+	commitID := strings.TrimSpace(string(data))
+	if !commitIDRE.MatchString(commitID) {
+		err := fmt.Errorf("%q is not a valid GitHub commit ID", commitID)
+		return "", err
+	}
+	return string(commitID[0:7]), nil
+}
+
+// readFileFromKoData tries to read data as string from the file with given name
+// under KO_DATA_PATH then returns the content as string. The file is expected
+// to be wrapped into the container from /kodata by ko. If it fails, returns
+// the error it gets.
+func readFileFromKoData(filename string) ([]byte, error) {
+	koDataPath := os.Getenv(koDataPathEnvName)
+	if koDataPath == "" {
+		err := fmt.Errorf("%q does not exist or is empty", koDataPathEnvName)
+		return nil, err
+	}
+	fullFilename := filepath.Join(koDataPath, filename)
+	return ioutil.ReadFile(fullFilename)
+}

changeset/commit_test.go

@@ -0,0 +1,88 @@
+/*
+Copyright 2018 The Knative 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 changeset
+
+import (
+	"fmt"
+	"os"
+	"testing"
+)
+
+const (
+	nonCommittedHeadContext = "ref: refs/heads/non_committed_branch"
+	testCommitID            = "a2d1bdf"
+)
+
+func TestReadFile(t *testing.T) {
+	tests := []struct {
+		name                      string
+		koDataPath                string
+		koDataPathEnvDoesNotExist bool
+		want                      string
+		wantErr                   bool
+		err                       error
+	}{{
+		name:       "committed branch",
+		koDataPath: "testdata",
+		want:       testCommitID,
+	}, {
+		name:       "non committed branch",
+		koDataPath: "testdata/noncommitted",
+		wantErr:    true,
+		err:        fmt.Errorf("%q is not a valid GitHub commit ID", nonCommittedHeadContext),
+	}, {
+		name:       "KO_DATA_PATH is empty",
+		koDataPath: "",
+		wantErr:    true,
+		err:        fmt.Errorf("%q does not exist or is empty", koDataPathEnvName),
+	}, {
+		name:                      "KO_DATA_PATH does not exist",
+		koDataPath:                "",
+		wantErr:                   true,
+		koDataPathEnvDoesNotExist: true,
+		err: fmt.Errorf("%q does not exist or is empty", koDataPathEnvName),
+	}, {
+		name:       "HEAD file does not exist",
+		koDataPath: "testdata/nonexisting",
+		wantErr:    true,
+		err:        fmt.Errorf("open testdata/nonexisting/HEAD: no such file or directory"),
+	}}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if test.koDataPathEnvDoesNotExist {
+				os.Clearenv()
+			} else {
+				os.Setenv(koDataPathEnvName, test.koDataPath)
+			}
+
+			got, err := Get()
+
+			if (err != nil) != test.wantErr {
+				t.Errorf("Get() = %v", err)
+			}
+			if !test.wantErr {
+				if test.want != got {
+					t.Errorf("wanted %q but got %q", test.want, got)
+				}
+			} else {
+				if err == nil || err.Error() != test.err.Error() {
+					t.Errorf("wanted error %v but got: %v", test.err, err)
+				}
+			}
+		})
+	}
+}

changeset/doc.go

@@ -0,0 +1,23 @@
+/*
+Copyright 2018 The Knative 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 changeset provides Knative utilities for fetching GitHub Commit ID
+// from kodata directory. It requires GitHub HEAD file to be linked into
+// Knative component source code via the following command:
+//   ln -s -r .git/HEAD ./cmd/<knative-component-name>/kodata/
+// Then ko will build this file into $KO_DATA_PATH when building the container
+// for a Knative component.
+package changeset

changeset/testdata/HEAD

@@ -0,0 +1 @@
+a2d1bdfe929516d7da141aef68631a7ee6941b2d

changeset/testdata/noncommitted/HEAD

@@ -0,0 +1 @@
+ref: refs/heads/non_committed_branch

logging/config.go

@@ -25,6 +25,7 @@ import (
 	"go.uber.org/zap/zapcore"
 	corev1 "k8s.io/api/core/v1"
 
+	"github.com/knative/pkg/changeset"
 	"github.com/knative/pkg/logging/logkey"
 )
 
@@ -37,7 +38,7 @@ import (
 func NewLogger(configJSON string, levelOverride string, opts ...zap.Option) (*zap.SugaredLogger, zap.AtomicLevel) {
 	logger, atomicLevel, err := newLoggerFromConfig(configJSON, levelOverride, opts)
 	if err == nil {
-		return logger.Sugar(), atomicLevel
+		return enrichLoggerWithCommitID(logger.Sugar()), atomicLevel
 	}
 
 	loggingCfg := zap.NewProductionConfig()
@@ -51,7 +52,18 @@ func NewLogger(configJSON string, levelOverride string, opts ...zap.Option) (*za
 	if err2 != nil {
 		panic(err2)
 	}
-	return logger.Named("fallback-logger").Sugar(), loggingCfg.Level
+	return enrichLoggerWithCommitID(logger.Named("fallback-logger").Sugar()), loggingCfg.Level
+}
+
+func enrichLoggerWithCommitID(logger *zap.SugaredLogger) *zap.SugaredLogger {
+	commmitID, err := changeset.Get()
+	if err == nil {
+		// Enrich logs with GitHub commit ID.
+		return logger.With(zap.String(logkey.GitHubCommitID, commmitID))
+	}
+
+	logger.Warnf("Fetch GitHub commit ID from kodata failed: %v", err)
+	return logger
 }
 
 // NewLoggerFromConfig creates a logger using the provided Config

logging/logkey/constants.go

@@ -55,4 +55,8 @@ const (
 
 	// KubernetesService is the key used to represent a Kubernetes service name in logs
 	KubernetesService = "knative.dev/k8sservice"
+
+	// GitHubCommitID is the key used to represent the GitHub Commit ID where the
+	// Knative component was built from in logs
+	GitHubCommitID = "commit"
 )