libs/log: [JSON format] include timestamp (#6174)

Closes #6146

CHANGELOG_PENDING.md

@@ -71,6 +71,7 @@ Friendly reminder, we have a [bug bounty program](https://hackerone.com/tendermi
 - [rpc/client/http] \#6163 Do not drop events even if the `out` channel is full (@melekes)
 - [node] \#6059 Validate and complete genesis doc before saving to state store (@silasdavis)
 - [state] \#6067 Batch save state data (@githubsands & @cmwaters)
+- [libs/log] \#6174 Include timestamp (`ts` field; `time.RFC3339Nano` format) in JSON logger output (@melekes)
 
 ### BUG FIXES
 

libs/cli/flags/log_level_test.go

@@ -15,7 +15,7 @@ const (
 
 func TestParseLogLevel(t *testing.T) {
 	var buf bytes.Buffer
-	jsonLogger := log.NewTMJSONLogger(&buf)
+	jsonLogger := log.NewTMJSONLoggerNoTS(&buf)
 
 	correctLogLevels := []struct {
 		lvl              string

libs/log/filter_test.go

@@ -58,7 +58,7 @@ func TestVariousLevels(t *testing.T) {
 		tc := tc
 		t.Run(tc.name, func(t *testing.T) {
 			var buf bytes.Buffer
-			logger := log.NewFilter(log.NewTMJSONLogger(&buf), tc.allowed)
+			logger := log.NewFilter(log.NewTMJSONLoggerNoTS(&buf), tc.allowed)
 
 			logger.Debug("here", "this is", "debug log")
 			logger.Info("here", "this is", "info log")
@@ -74,7 +74,7 @@ func TestVariousLevels(t *testing.T) {
 func TestLevelContext(t *testing.T) {
 	var buf bytes.Buffer
 
-	logger := log.NewTMJSONLogger(&buf)
+	logger := log.NewTMJSONLoggerNoTS(&buf)
 	logger = log.NewFilter(logger, log.AllowError())
 	logger = logger.With("context", "value")
 
@@ -96,7 +96,7 @@ func TestLevelContext(t *testing.T) {
 func TestVariousAllowWith(t *testing.T) {
 	var buf bytes.Buffer
 
-	logger := log.NewTMJSONLogger(&buf)
+	logger := log.NewTMJSONLoggerNoTS(&buf)
 
 	logger1 := log.NewFilter(logger, log.AllowError(), log.AllowInfoWith("context", "value"))
 	logger1.With("context", "value").Info("foo", "bar", "baz")

libs/log/tm_json_logger.go

@@ -11,5 +11,14 @@ import (
 // w.Write. The passed Writer must be safe for concurrent use by multiple
 // goroutines if the returned Logger will be used concurrently.
 func NewTMJSONLogger(w io.Writer) Logger {
-	return &tmLogger{kitlog.NewJSONLogger(w)}
+	logger := kitlog.NewJSONLogger(w)
+	logger = kitlog.With(logger, "ts", kitlog.DefaultTimestampUTC)
+	return &tmLogger{logger}
+}
+
+// NewTMJSONLoggerNoTS is the same as NewTMJSONLogger, but without the
+// timestamp.
+func NewTMJSONLoggerNoTS(w io.Writer) Logger {
+	logger := kitlog.NewJSONLogger(w)
+	return &tmLogger{logger}
 }

libs/log/tracing_logger_test.go

@@ -15,7 +15,7 @@ import (
 func TestTracingLogger(t *testing.T) {
 	var buf bytes.Buffer
 
-	logger := log.NewTMJSONLogger(&buf)
+	logger := log.NewTMJSONLoggerNoTS(&buf)
 
 	logger1 := log.NewTracingLogger(logger)
 	err1 := errors.New("courage is grace under pressure")