Add a func converting go-kit log to slog

go.mod

@@ -120,6 +120,7 @@ require (
 	github.com/onsi/gomega v1.34.0
 	github.com/prometheus-community/prom-label-proxy v0.8.1-0.20240127162815-c1195f9aabc0
 	github.com/seiflotfy/cuckoofilter v0.0.0-20240715131351-a2f2c23f1771
+	github.com/tjhop/slog-gokit v0.1.2
 	go.opentelemetry.io/contrib/propagators/autoprop v0.54.0
 	go4.org/intern v0.0.0-20230525184215-6c62f75575cb
 	golang.org/x/exp v0.0.0-20240613232115-7f521ea00fb8

go.sum

@@ -2263,6 +2263,8 @@ github.com/themihai/gomemcache v0.0.0-20180902122335-24332e2d58ab h1:7ZR3hmisBWw
 github.com/themihai/gomemcache v0.0.0-20180902122335-24332e2d58ab/go.mod h1:eheTFp954zcWZXCU8d0AT76ftsQOTo4DTqkN/h3k1MY=
 github.com/tinylib/msgp v1.1.5 h1:2gXmtWueD2HefZHQe1QOy9HVzmFrLOVvsXwXBQ0ayy0=
 github.com/tinylib/msgp v1.1.5/go.mod h1:eQsjooMTnV42mHu917E26IogZ2930nFyBQdofk10Udg=
+github.com/tjhop/slog-gokit v0.1.2 h1:pmQI4SvU9h4gA0vIQsdhJQSqQg4mOmsPykG2/PM3j1I=
+github.com/tjhop/slog-gokit v0.1.2/go.mod h1:8fhlcp8C8ELbg3GCyKv06tgt4B5sDq2P1r2DQAu1HuM=
 github.com/tklauser/go-sysconf v0.3.4/go.mod h1:Cl2c8ZRWfHD5IrfHo9VN+FX9kCFjIOyVklgXycLB6ek=
 github.com/tklauser/go-sysconf v0.3.10 h1:IJ1AZGZRWbY8T5Vfk04D9WOA5WSejdflXxP03OUqALw=
 github.com/tklauser/go-sysconf v0.3.10/go.mod h1:C8XykCvCb+Gn0oNCWPIlcb0RuglQTYaQ2hGm7jmxEFk=

pkg/logging/logger.go

@@ -15,6 +15,11 @@ const (
 	LogFormatJSON   = "json"
 )
 
+type LevelLogger struct {
+	log.Logger
+	LogLevel string
+}
+
 // NewLogger returns a log.Logger that prints in the provided format at the
 // provided level with a UTC timestamp and the caller of the log entry. If non
 // empty, the debug name is also appended as a field to all log lines. Panics
@@ -55,5 +60,8 @@ func NewLogger(logLevel, logFormat, debugName string) log.Logger {
 		logger = log.With(logger, "name", debugName)
 	}
 
-	return logger
+	return LevelLogger{
+		Logger:   logger,
+		LogLevel: logLevel,
+	}
 }

pkg/logutil/logutil.go

@@ -0,0 +1,33 @@
+// Copyright (c) The Thanos Authors.
+// Licensed under the Apache License 2.0.
+
+package logutil
+
+import (
+	"log/slog"
+
+	"github.com/go-kit/log"
+	"github.com/thanos-io/thanos/pkg/logging"
+	sloggk "github.com/tjhop/slog-gokit"
+)
+
+// GoKitLogToSlog convert go-kit/log to slog.
+func GoKitLogToSlog(logger log.Logger) *slog.Logger {
+	levelVar := slog.LevelVar{}
+	levelLogger, ok := logger.(logging.LevelLogger)
+	if !ok {
+		levelVar.Set(slog.LevelDebug)
+	} else {
+		switch levelLogger.LogLevel {
+		case "debug":
+			levelVar.Set(slog.LevelDebug)
+		case "info":
+			levelVar.Set(slog.LevelInfo)
+		case "warn":
+			levelVar.Set(slog.LevelWarn)
+		case "error":
+			levelVar.Set(slog.LevelError)
+		}
+	}
+	return slog.New(sloggk.NewGoKitHandler(logger, &levelVar))
+}

pkg/logutil/logutil_test.go

@@ -0,0 +1,52 @@
+// Copyright (c) The Thanos Authors.
+// Licensed under the Apache License 2.0.
+
+package logutil
+
+import (
+	"context"
+	"log/slog"
+	"testing"
+
+	"github.com/go-kit/log/level"
+	"github.com/stretchr/testify/require"
+	"github.com/thanos-io/thanos/pkg/logging"
+)
+
+func Test_GoKitLogToSlog(t *testing.T) {
+	ctx := context.Background()
+	logLevels := []string{"debug", "info", "warn", "error"}
+	slogLevels := []slog.Level{slog.LevelDebug, slog.LevelInfo, slog.LevelWarn, slog.LevelError}
+
+	for _, logFormat := range []string{"logfmt", "json"} {
+		for i, lv := range logLevels {
+			logger := logging.NewLogger(lv, logFormat, "test")
+
+			slog := GoKitLogToSlog(logger)
+			for j, slogLv := range slogLevels {
+				if i <= j {
+					t.Logf("[logFormat: %v, go-kit log level: %v, slog level: %v] slog should be enabled", logFormat, lv, slogLv)
+					require.True(t, slog.Enabled(ctx, slogLv))
+				} else {
+					t.Logf("[logFormat: %v, go-kit log level: %v, slog level: %v] slog should be disabled", logFormat, lv, slogLv)
+					require.False(t, slog.Enabled(ctx, slogLv))
+				}
+
+				switch lv {
+				case "debug":
+					level.Debug(logger).Log("msg", "message", "debug", lv)
+					slog.Debug("message", "debug", lv)
+				case "info":
+					level.Info(logger).Log("msg", "message", "info", lv)
+					slog.Info("message", "info", lv)
+				case "warn":
+					level.Warn(logger).Log("msg", "message", "warn", lv)
+					slog.Warn("message", "warn", lv)
+				case "error":
+					level.Error(logger).Log("msg", "message", "error", lv)
+					slog.Error("message", "error", lv)
+				}
+			}
+		}
+	}
+}