From 72f8fce10701ae218f14d2df60a4c18211b0cf0c Mon Sep 17 00:00:00 2001
From: Michal Kralik <michal.kralik@percona.com>
Date: Sat, 17 Dec 2022 02:26:32 +0100
Subject: [PATCH] lib/logger: support for renaming json fields (#3488)

---
 lib/logger/json-fields.go | 32 ++++++++++++++++++++++++++++++++
 lib/logger/logger.go      | 25 +++++++++++++++++++------
 2 files changed, 51 insertions(+), 6 deletions(-)
 create mode 100644 lib/logger/json-fields.go

diff --git a/lib/logger/json-fields.go b/lib/logger/json-fields.go
new file mode 100644
index 000000000..6ce5be497
--- /dev/null
+++ b/lib/logger/json-fields.go
@@ -0,0 +1,32 @@
+package logger
+
+import "strings"
+
+var (
+	fieldTs     = "ts"
+	fieldLevel  = "level"
+	fieldCaller = "caller"
+	fieldMsg    = "msg"
+)
+
+func setLoggerJSONFields() {
+	fields := strings.Split(*loggerJSONFields, ",")
+	for _, f := range fields {
+		v := strings.Split(strings.TrimSpace(f), ":")
+		if len(v) != 2 {
+			continue
+		}
+
+		old, new := v[0], v[1]
+		switch old {
+		case "ts":
+			fieldTs = new
+		case "level":
+			fieldLevel = new
+		case "caller":
+			fieldCaller = new
+		case "msg":
+			fieldMsg = new
+		}
+	}
+}
diff --git a/lib/logger/logger.go b/lib/logger/logger.go
index 840cf8bf1..83938fce7 100644
--- a/lib/logger/logger.go
+++ b/lib/logger/logger.go
@@ -17,10 +17,11 @@ import (
 )
 
 var (
-	loggerLevel    = flag.String("loggerLevel", "INFO", "Minimum level of errors to log. Possible values: INFO, WARN, ERROR, FATAL, PANIC")
-	loggerFormat   = flag.String("loggerFormat", "default", "Format for logs. Possible values: default, json")
-	loggerOutput   = flag.String("loggerOutput", "stderr", "Output for the logs. Supported values: stderr, stdout")
-	loggerTimezone = flag.String("loggerTimezone", "UTC", "Timezone to use for timestamps in logs. Timezone must be a valid IANA Time Zone. "+
+	loggerLevel      = flag.String("loggerLevel", "INFO", "Minimum level of errors to log. Possible values: INFO, WARN, ERROR, FATAL, PANIC")
+	loggerFormat     = flag.String("loggerFormat", "default", "Format for logs. Possible values: default, json")
+	loggerOutput     = flag.String("loggerOutput", "stderr", "Output for the logs. Supported values: stderr, stdout")
+	loggerJSONFields = flag.String("loggerJsonFields", "", `Allows renaming fields in JSON formatted logs. Example: "ts:timestamp,msg:message" renames "ts" to "timestamp" and "msg" to "message"`)
+	loggerTimezone   = flag.String("loggerTimezone", "UTC", "Timezone to use for timestamps in logs. Timezone must be a valid IANA Time Zone. "+
 		"For example: America/New_York, Europe/Berlin, Etc/GMT+3 or Local")
 	disableTimestamps = flag.Bool("loggerDisableTimestamps", false, "Whether to disable writing timestamps in logs")
 
@@ -34,6 +35,7 @@ var (
 //
 // There is no need in calling Init from tests.
 func Init() {
+	setLoggerJSONFields()
 	setLoggerOutput()
 	validateLoggerLevel()
 	validateLoggerFormat()
@@ -239,9 +241,20 @@ func logMessage(level, msg string, skipframes int) {
 	switch *loggerFormat {
 	case "json":
 		if *disableTimestamps {
-			logMsg = fmt.Sprintf(`{"level":%q,"caller":%q,"msg":%q}`+"\n", levelLowercase, location, msg)
+			logMsg = fmt.Sprintf(
+				`{%q:%q,%q:%q,%q:%q}`+"\n",
+				fieldLevel, levelLowercase,
+				fieldCaller, location,
+				fieldMsg, msg,
+			)
 		} else {
-			logMsg = fmt.Sprintf(`{"ts":%q,"level":%q,"caller":%q,"msg":%q}`+"\n", timestamp, levelLowercase, location, msg)
+			logMsg = fmt.Sprintf(
+				`{%q:%q,%q:%q,%q:%q,%q:%q}`+"\n",
+				fieldTs, timestamp,
+				fieldLevel, levelLowercase,
+				fieldCaller, location,
+				fieldMsg, msg,
+			)
 		}
 	default:
 		if *disableTimestamps {