🌱 cron: structured logging (#3167)

* Structured logging for cron

Signed-off-by: Raghav Kaul <raghavkaul@google.com>

* also update scorecard worker logger

Signed-off-by: Raghav Kaul <raghavkaul@google.com>

* address pr comments

* set json fields
* docs link

---------

Signed-off-by: Raghav Kaul <raghavkaul@google.com>

cron/internal/worker/main.go

@@ -118,7 +118,7 @@ func newScorecardWorker() (*ScorecardWorker, error) {
 	}
 
 	sw.ctx = context.Background()
-	sw.logger = log.NewLogger(log.InfoLevel)
+	sw.logger = log.NewCronLogger(log.InfoLevel)
 	sw.githubClient = githubrepo.CreateGithubRepoClient(sw.ctx, sw.logger)
 	// TODO(raghavkaul): Read GitLab auth token from environment
 	if sw.gitlabClient, err = gitlabrepo.CreateGitlabClient(sw.ctx, "https://gitlab.com"); err != nil {

cron/worker/worker.go

@@ -74,7 +74,7 @@ func (wl *WorkLoop) Run() error {
 		return fmt.Errorf("config.GetResultDataBucketURL: %w", err)
 	}
 
-	logger := log.NewLogger(log.InfoLevel)
+	logger := log.NewCronLogger(log.InfoLevel)
 
 	for {
 		req, err := subscriber.SynchronousPull()

log/log.go

@@ -41,6 +41,23 @@ func NewLogger(logLevel Level) *Logger {
 	return NewLogrusLogger(logrusLog)
 }
 
+// NewCronLogger creates an instance of *Logger.
+func NewCronLogger(logLevel Level) *Logger {
+	logrusLog := logrus.New()
+
+	// for stackdriver, see: https://cloud.google.com/logging/docs/structured-logging#special-payload-fields
+	logrusLog.SetFormatter(&logrus.JSONFormatter{FieldMap: logrus.FieldMap{
+		logrus.FieldKeyLevel: "severity",
+		logrus.FieldKeyMsg:   "message",
+	}})
+
+	// Set log level from logrus
+	logrusLevel := parseLogrusLevel(logLevel)
+	logrusLog.SetLevel(logrusLevel)
+
+	return NewLogrusLogger(logrusLog)
+}
+
 // NewLogrusLogger creates an instance of *Logger backed by the supplied
 // logrusLog instance.
 func NewLogrusLogger(logrusLog *logrus.Logger) *Logger {