feat: replace go-kit logger by slog

Makefile

@@ -16,7 +16,7 @@ endif
 
 GOBUILD ?= CGO_ENABLED=0 go build
 PACKAGES ?= $(shell go list ./...)
-SOURCES ?= $(shell find . -name "*.go" -type f)
+SOURCES ?= $(shell find . -name "*.go" -type f -not -path ./.devenv/\* -not -path ./.direnv/\*)
 GENERATE ?= $(PACKAGES)
 
 TAGS ?= netgo

changelog/unreleased/logging-library.md

@@ -0,0 +1,7 @@
+Change: Switch to official logging library
+
+Since there have been a structured logger part of the Go standard library we
+thought it's time to replace the library with that. Be aware that log messages
+should change a little bit.
+
+https://github.com/promhippie/hetzner_exporter/issues/196

pkg/action/metrics.go

@@ -2,9 +2,8 @@ package action
 
 import (
 	"fmt"
+	"log/slog"
 
-	"github.com/go-kit/log"
-	"github.com/go-kit/log/level"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/collectors"
 	"github.com/promhippie/hetzner_exporter/pkg/version"
@@ -49,11 +48,9 @@ func init() {
 }
 
 type promLogger struct {
-	logger log.Logger
+	logger *slog.Logger
 }
 
 func (pl promLogger) Println(v ...interface{}) {
-	level.Error(pl.logger).Log(
-		"msg", fmt.Sprintln(v...),
-	)
+	pl.logger.Error(fmt.Sprintln(v...))
 }

pkg/action/server.go

@@ -3,14 +3,13 @@ package action
 import (
 	"context"
 	"io"
+	"log/slog"
 	"net/http"
 	"os"
 	"os/signal"
 	"time"
 
 	"github.com/go-chi/chi/v5"
-	"github.com/go-kit/log"
-	"github.com/go-kit/log/level"
 	"github.com/oklog/run"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/prometheus/exporter-toolkit/web"
@@ -22,9 +21,8 @@ import (
 )
 
 // Server handles the server sub-command.
-func Server(cfg *config.Config, logger log.Logger) error {
-	level.Info(logger).Log(
-		"msg", "Launching Hetzner Exporter",
+func Server(cfg *config.Config, logger *slog.Logger) error {
+	logger.Info("Launching Hetzner Exporter",
 		"version", version.String,
 		"revision", version.Revision,
 		"date", version.Date,
@@ -34,8 +32,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 	username, err := config.Value(cfg.Target.Username)
 
 	if err != nil {
-		level.Error(logger).Log(
-			"msg", "Failed to load username from file",
+		logger.Error("Failed to load username from file",
 			"err", err,
 		)
 
@@ -45,8 +42,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 	password, err := config.Value(cfg.Target.Password)
 
 	if err != nil {
-		level.Error(logger).Log(
-			"msg", "Failed to load password from file",
+		logger.Error("Failed to load password from file",
 			"err", err,
 		)
 
@@ -69,9 +65,8 @@ func Server(cfg *config.Config, logger log.Logger) error {
 		}
 
 		gr.Add(func() error {
-			level.Info(logger).Log(
-				"msg", "Starting metrics server",
-				"addr", cfg.Server.Addr,
+			logger.Info("Starting metrics server",
+				"address", cfg.Server.Addr,
 			)
 
 			return web.ListenAndServe(
@@ -88,16 +83,14 @@ func Server(cfg *config.Config, logger log.Logger) error {
 			defer cancel()
 
 			if err := server.Shutdown(ctx); err != nil {
-				level.Error(logger).Log(
-					"msg", "Failed to shutdown metrics gracefully",
+				logger.Error("Failed to shutdown metrics gracefully",
 					"err", err,
 				)
 
 				return
 			}
 
-			level.Info(logger).Log(
-				"msg", "Metrics shutdown gracefully",
+			logger.Info("Metrics shutdown gracefully",
 				"reason", reason,
 			)
 		})
@@ -120,7 +113,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 	return gr.Run()
 }
 
-func handler(cfg *config.Config, logger log.Logger, client *hetzner.Client) *chi.Mux {
+func handler(cfg *config.Config, logger *slog.Logger, client *hetzner.Client) *chi.Mux {
 	mux := chi.NewRouter()
 	mux.Use(middleware.Recoverer(logger))
 	mux.Use(middleware.RealIP)
@@ -132,9 +125,7 @@ func handler(cfg *config.Config, logger log.Logger, client *hetzner.Client) *chi
 	}
 
 	if cfg.Collector.Servers {
-		level.Debug(logger).Log(
-			"msg", "Server collector registered",
-		)
+		logger.Debug("Server collector registered")
 
 		registry.MustRegister(exporter.NewServerCollector(
 			logger,
@@ -146,9 +137,7 @@ func handler(cfg *config.Config, logger log.Logger, client *hetzner.Client) *chi
 	}
 
 	if cfg.Collector.SSHKeys {
-		level.Debug(logger).Log(
-			"msg", "SSH key collector registered",
-		)
+		logger.Debug("SSH key collector registered")
 
 		registry.MustRegister(exporter.NewSSHKeyCollector(
 			logger,
@@ -160,9 +149,7 @@ func handler(cfg *config.Config, logger log.Logger, client *hetzner.Client) *chi
 	}
 
 	if cfg.Collector.Storageboxes {
-		level.Debug(logger).Log(
-			"msg", "Storagebox collector registered",
-		)
+		logger.Debug("Storagebox collector registered")
 
 		registry.MustRegister(exporter.NewStorageboxCollector(
 			logger,

pkg/command/command.go

@@ -5,7 +5,6 @@ import (
 	"os"
 	"time"
 
-	"github.com/go-kit/log/level"
 	"github.com/promhippie/hetzner_exporter/pkg/action"
 	"github.com/promhippie/hetzner_exporter/pkg/config"
 	"github.com/promhippie/hetzner_exporter/pkg/version"
@@ -34,18 +33,12 @@ func Run() error {
 			logger := setupLogger(cfg)
 
 			if cfg.Target.Username == "" {
-				level.Error(logger).Log(
-					"msg", "Missing required hetzner.username",
-				)
-
+				logger.Error("Missing required hetzner.username")
 				return fmt.Errorf("missing required hetzner.username")
 			}
 
 			if cfg.Target.Password == "" {
-				level.Error(logger).Log(
-					"msg", "Missing required hetzner.password",
-				)
-
+				logger.Error("Missing required hetzner.password")
 				return fmt.Errorf("missing required hetzner.password")
 			}
 

pkg/command/health.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 	"net/http"
 
-	"github.com/go-kit/log/level"
 	"github.com/promhippie/hetzner_exporter/pkg/config"
 	"github.com/urfave/cli/v2"
 )
@@ -26,8 +25,7 @@ func Health(cfg *config.Config) *cli.Command {
 			)
 
 			if err != nil {
-				level.Error(logger).Log(
-					"msg", "Failed to request health check",
+				logger.Error("Failed to request health check",
 					"err", err,
 				)
 
@@ -37,15 +35,18 @@ func Health(cfg *config.Config) *cli.Command {
 			defer resp.Body.Close()
 
 			if resp.StatusCode != 200 {
-				level.Error(logger).Log(
-					"msg", "Health check seems to be in bad state",
+				logger.Error("Health check seems to be in bad state",
 					"err", err,
 					"code", resp.StatusCode,
 				)
 
 				return err
 			}
 
+			logger.Debug("Health check seems to be fine",
+				"code", resp.StatusCode,
+			)
+
 			return nil
 		},
 	}

pkg/command/setup.go

@@ -1,42 +1,40 @@
 package command
 
 import (
+	"log/slog"
 	"os"
 	"strings"
 
-	"github.com/go-kit/log"
-	"github.com/go-kit/log/level"
 	"github.com/promhippie/hetzner_exporter/pkg/config"
 )
 
-func setupLogger(cfg *config.Config) log.Logger {
-	var logger log.Logger
-
+func setupLogger(cfg *config.Config) *slog.Logger {
 	if cfg.Logs.Pretty {
-		logger = log.NewSyncLogger(
-			log.NewLogfmtLogger(os.Stdout),
-		)
-	} else {
-		logger = log.NewSyncLogger(
-			log.NewJSONLogger(os.Stdout),
+		return slog.New(
+			slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
+				Level: loggerLevel(cfg),
+			}),
 		)
 	}
 
+	return slog.New(
+		slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
+			Level: loggerLevel(cfg),
+		}),
+	)
+}
+
+func loggerLevel(cfg *config.Config) slog.Leveler {
 	switch strings.ToLower(cfg.Logs.Level) {
 	case "error":
-		logger = level.NewFilter(logger, level.AllowError())
+		return slog.LevelError
 	case "warn":
-		logger = level.NewFilter(logger, level.AllowWarn())
+		return slog.LevelWarn
 	case "info":
-		logger = level.NewFilter(logger, level.AllowInfo())
+		return slog.LevelInfo
 	case "debug":
-		logger = level.NewFilter(logger, level.AllowDebug())
-	default:
-		logger = level.NewFilter(logger, level.AllowInfo())
+		return slog.LevelDebug
 	}
 
-	return log.With(
-		logger,
-		"ts", log.DefaultTimestampUTC,
-	)
+	return slog.LevelInfo
 }

pkg/exporter/server.go

@@ -2,10 +2,9 @@ package exporter
 
 import (
 	"context"
+	"log/slog"
 	"time"
 
-	"github.com/go-kit/log"
-	"github.com/go-kit/log/level"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/promhippie/hetzner_exporter/pkg/config"
 	"github.com/promhippie/hetzner_exporter/pkg/internal/hetzner"
@@ -14,7 +13,7 @@ import (
 // ServerCollector collects metrics about the account in general.
 type ServerCollector struct {
 	client   *hetzner.Client
-	logger   log.Logger
+	logger   *slog.Logger
 	failures *prometheus.CounterVec
 	duration *prometheus.HistogramVec
 	config   config.Target
@@ -27,15 +26,15 @@ type ServerCollector struct {
 }
 
 // NewServerCollector returns a new ServerCollector.
-func NewServerCollector(logger log.Logger, client *hetzner.Client, failures *prometheus.CounterVec, duration *prometheus.HistogramVec, cfg config.Target) *ServerCollector {
+func NewServerCollector(logger *slog.Logger, client *hetzner.Client, failures *prometheus.CounterVec, duration *prometheus.HistogramVec, cfg config.Target) *ServerCollector {
 	if failures != nil {
 		failures.WithLabelValues("account").Add(0)
 	}
 
 	labels := []string{"id", "name", "datacenter"}
 	return &ServerCollector{
 		client:   client,
-		logger:   log.With(logger, "collector", "server"),
+		logger:   logger.With("collector", "server"),
 		failures: failures,
 		duration: duration,
 		config:   cfg,
@@ -103,17 +102,15 @@ func (c *ServerCollector) Collect(ch chan<- prometheus.Metric) {
 	c.duration.WithLabelValues("server").Observe(time.Since(now).Seconds())
 
 	if err != nil {
-		level.Error(c.logger).Log(
-			"msg", "Failed to fetch servers",
+		c.logger.Error("Failed to fetch servers",
 			"err", err,
 		)
 
 		c.failures.WithLabelValues("server").Inc()
 		return
 	}
 
-	level.Debug(c.logger).Log(
-		"msg", "Fetched servers",
+	c.logger.Debug("Fetched servers",
 		"count", len(servers),
 	)