TUN-9371: Add logging format as JSON

Closes TUN-9371

logger/configuration.go

@@ -17,6 +17,7 @@ type Config struct {
 
 type ConsoleConfig struct {
 	noColor bool
+	asJSON  bool
 }
 
 type FileConfig struct {
@@ -48,6 +49,7 @@ func createDefaultConfig() Config {
 	return Config{
 		ConsoleConfig: &ConsoleConfig{
 			noColor: false,
+			asJSON:  false,
 		},
 		FileConfig: &FileConfig{
 			Dirname:  "",
@@ -67,11 +69,12 @@ func createDefaultConfig() Config {
 func CreateConfig(
 	minLevel string,
 	disableTerminal bool,
+	formatJSON bool,
 	rollingLogPath, nonRollingLogFilePath string,
 ) *Config {
 	var console *ConsoleConfig
 	if !disableTerminal {
-		console = createConsoleConfig()
+		console = createConsoleConfig(formatJSON)
 	}
 
 	var file *FileConfig
@@ -95,9 +98,10 @@ func CreateConfig(
 	}
 }
 
-func createConsoleConfig() *ConsoleConfig {
+func createConsoleConfig(formatJSON bool) *ConsoleConfig {
 	return &ConsoleConfig{
 		noColor: false,
+		asJSON:  formatJSON,
 	}
 }
 

logger/console.go

@@ -0,0 +1,37 @@
+package logger
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	jsoniter "github.com/json-iterator/go"
+)
+
+var json = jsoniter.ConfigCompatibleWithStandardLibrary
+
+// consoleWriter allows us the simplicity to prevent duplicate json keys in the logger events reported.
+//
+// By default zerolog constructs the json event in parts by appending each additional key after the first. It
+// doesn't have any internal state or struct of the json message representation so duplicate keys can be
+// inserted without notice and no pruning will occur before writing the log event out to the io.Writer.
+//
+// To help prevent these duplicate keys, we will decode the json log event and then immediately re-encode it
+// again as writing it to the output io.Writer. Since we encode it to a map[string]any, duplicate keys
+// are pruned. We pay the cost of decoding and encoding the log event for each time, but helps prevent
+// us from needing to worry about adding duplicate keys in the log event from different areas of code.
+type consoleWriter struct {
+	out io.Writer
+}
+
+func (c *consoleWriter) Write(p []byte) (n int, err error) {
+	var evt map[string]any
+	d := json.NewDecoder(bytes.NewReader(p))
+	d.UseNumber()
+	err = d.Decode(&evt)
+	if err != nil {
+		return n, fmt.Errorf("cannot decode event: %s", err)
+	}
+	e := json.NewEncoder(c.out)
+	return len(p), e.Encode(evt)
+}

logger/console_test.go

@@ -0,0 +1,33 @@
+package logger
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"github.com/rs/zerolog"
+)
+
+func TestConsoleLoggerDuplicateKeys(t *testing.T) {
+	r := bytes.NewBuffer(make([]byte, 500))
+	logger := zerolog.New(&consoleWriter{out: r}).With().Timestamp().Logger()
+	logger.Debug().Str("test", "1234").Int("number", 45).Str("test", "5678").Msg("log message")
+
+	event, err := r.ReadString('\n')
+	if err != nil {
+		t.Error(err)
+	}
+
+	if !strings.Contains(event, "\"test\":\"5678\"") {
+		t.Errorf("log event missing key 'test': %s", event)
+	}
+	if !strings.Contains(event, "\"number\":45") {
+		t.Errorf("log event missing key 'number': %s", event)
+	}
+	if !strings.Contains(event, "\"time\":") {
+		t.Errorf("log event missing key 'time': %s", event)
+	}
+	if !strings.Contains(event, "\"level\":\"debug\"") {
+		t.Errorf("log event missing key 'level': %s", event)
+	}
+}

logger/create.go

@@ -149,10 +149,21 @@ func createFromContext(
 	logLevel := c.String(logLevelFlagName)
 	logFile := c.String(cfdflags.LogFile)
 	logDirectory := c.String(logDirectoryFlagName)
+	var logFormatJSON bool
+	switch c.String(cfdflags.LogFormatOutput) {
+	case cfdflags.LogFormatOutputValueJSON:
+		logFormatJSON = true
+	case cfdflags.LogFormatOutputValueDefault:
+		// "default" and unset use the same logger output format
+		fallthrough
+	default:
+		logFormatJSON = false
+	}
 
 	loggerConfig := CreateConfig(
 		logLevel,
 		disableTerminal,
+		logFormatJSON,
 		logDirectory,
 		logFile,
 	)
@@ -177,6 +188,9 @@ func Create(loggerConfig *Config) *zerolog.Logger {
 }
 
 func createConsoleLogger(config ConsoleConfig) io.Writer {
+	if config.asJSON {
+		return &consoleWriter{out: os.Stderr}
+	}
 	consoleOut := os.Stderr
 	return zerolog.ConsoleWriter{
 		Out:        colorable.NewColorable(consoleOut),