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/scw_exporter/issues/104

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/scw_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

@@ -4,14 +4,13 @@ import (
 	"context"
 	"fmt"
 	"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"
@@ -23,9 +22,8 @@ import (
 )
 
 // Server handles the server sub-command.
-func Server(cfg *config.Config, logger log.Logger) error {
-	level.Info(logger).Log(
-		"msg", "Launching Scaleway Exporter",
+func Server(cfg *config.Config, logger *slog.Logger) error {
+	logger.Info("Launching Scaleway Exporter",
 		"version", version.String,
 		"revision", version.Revision,
 		"date", version.Date,
@@ -35,8 +33,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 	accessKey, err := config.Value(cfg.Target.AccessKey)
 
 	if err != nil {
-		level.Error(logger).Log(
-			"msg", "Failed to load access key from file",
+		logger.Error("Failed to load access key from file",
 			"err", err,
 		)
 
@@ -46,8 +43,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 	secretKey, err := config.Value(cfg.Target.SecretKey)
 
 	if err != nil {
-		level.Error(logger).Log(
-			"msg", "Failed to load secret key from file",
+		logger.Error("Failed to load secret key from file",
 			"err", err,
 		)
 
@@ -88,8 +84,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 		)
 
 		if err != nil {
-			level.Error(logger).Log(
-				"msg", "Failed to parse region",
+			logger.Error("Failed to parse region",
 				"err", err,
 			)
 
@@ -107,8 +102,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 		)
 
 		if err != nil {
-			level.Error(logger).Log(
-				"msg", "Failed to parse zone",
+			logger.Error("Failed to parse zone",
 				"err", err,
 			)
 
@@ -125,8 +119,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 	)
 
 	if err != nil {
-		level.Error(logger).Log(
-			"msg", "Failed to initialize Scaleway client",
+		logger.Error("Failed to initialize Scaleway client",
 			"err", err,
 		)
 
@@ -144,9 +137,8 @@ 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(
@@ -163,16 +155,14 @@ 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,
 			)
 		})
@@ -195,7 +185,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 	return gr.Run()
 }
 
-func handler(cfg *config.Config, logger log.Logger, client *scw.Client) *chi.Mux {
+func handler(cfg *config.Config, logger *slog.Logger, client *scw.Client) *chi.Mux {
 	mux := chi.NewRouter()
 	mux.Use(middleware.Recoverer(logger))
 	mux.Use(middleware.RealIP)
@@ -207,9 +197,7 @@ func handler(cfg *config.Config, logger log.Logger, client *scw.Client) *chi.Mux
 	}
 
 	if cfg.Collector.Dashboard {
-		level.Debug(logger).Log(
-			"msg", "Dashboard collector registered",
-		)
+		logger.Debug("Dashboard collector registered")
 
 		registry.MustRegister(exporter.NewDashboardCollector(
 			logger,
@@ -221,9 +209,7 @@ func handler(cfg *config.Config, logger log.Logger, client *scw.Client) *chi.Mux
 	}
 
 	if cfg.Collector.SecurityGroups {
-		level.Debug(logger).Log(
-			"msg", "Security group collector registered",
-		)
+		logger.Debug("Security group collector registered")
 
 		registry.MustRegister(exporter.NewSecurityGroupCollector(
 			logger,
@@ -235,9 +221,7 @@ func handler(cfg *config.Config, logger log.Logger, client *scw.Client) *chi.Mux
 	}
 
 	if cfg.Collector.Servers {
-		level.Debug(logger).Log(
-			"msg", "Server collector registered",
-		)
+		logger.Debug("Server collector registered")
 
 		registry.MustRegister(exporter.NewServerCollector(
 			logger,
@@ -249,9 +233,7 @@ func handler(cfg *config.Config, logger log.Logger, client *scw.Client) *chi.Mux
 	}
 
 	if cfg.Collector.Snapshots {
-		level.Debug(logger).Log(
-			"msg", "Snaptshot collector registered",
-		)
+		logger.Debug("Snaptshot collector registered")
 
 		registry.MustRegister(exporter.NewSnapshotCollector(
 			logger,
@@ -263,9 +245,7 @@ func handler(cfg *config.Config, logger log.Logger, client *scw.Client) *chi.Mux
 	}
 
 	if cfg.Collector.Volumes {
-		level.Debug(logger).Log(
-			"msg", "Volume collector registered",
-		)
+		logger.Debug("Volume collector registered")
 
 		registry.MustRegister(exporter.NewVolumeCollector(
 			logger,

pkg/command/command.go

@@ -5,7 +5,6 @@ import (
 	"os"
 	"time"
 
-	"github.com/go-kit/log/level"
 	"github.com/promhippie/scw_exporter/pkg/action"
 	"github.com/promhippie/scw_exporter/pkg/config"
 	"github.com/promhippie/scw_exporter/pkg/version"
@@ -34,18 +33,12 @@ func Run() error {
 			logger := setupLogger(cfg)
 
 			if cfg.Target.AccessKey == "" {
-				level.Error(logger).Log(
-					"msg", "Missing required scw.access-key",
-				)
-
+				logger.Error("Missing required scw.access-key")
 				return fmt.Errorf("missing required scw.access-key")
 			}
 
 			if cfg.Target.SecretKey == "" {
-				level.Error(logger).Log(
-					"msg", "Missing required scw.secret-key",
-				)
-
+				logger.Error("Missing required scw.secret-key")
 				return fmt.Errorf("missing required scw.secret-key")
 			}
 

pkg/command/health.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 	"net/http"
 
-	"github.com/go-kit/log/level"
 	"github.com/promhippie/scw_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/scw_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/dashboard.go

@@ -1,10 +1,9 @@
 package exporter
 
 import (
+	"log/slog"
 	"time"
 
-	"github.com/go-kit/log"
-	"github.com/go-kit/log/level"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/promhippie/scw_exporter/pkg/config"
 	"github.com/scaleway/scaleway-sdk-go/api/instance/v1"
@@ -15,7 +14,7 @@ import (
 type DashboardCollector struct {
 	client   *scw.Client
 	instance *instance.API
-	logger   log.Logger
+	logger   *slog.Logger
 	failures *prometheus.CounterVec
 	duration *prometheus.HistogramVec
 	config   config.Target
@@ -40,7 +39,7 @@ type DashboardCollector struct {
 }
 
 // NewDashboardCollector returns a new DashboardCollector.
-func NewDashboardCollector(logger log.Logger, client *scw.Client, failures *prometheus.CounterVec, duration *prometheus.HistogramVec, cfg config.Target) *DashboardCollector {
+func NewDashboardCollector(logger *slog.Logger, client *scw.Client, failures *prometheus.CounterVec, duration *prometheus.HistogramVec, cfg config.Target) *DashboardCollector {
 	if failures != nil {
 		failures.WithLabelValues("dashboard").Add(0)
 	}
@@ -49,7 +48,7 @@ func NewDashboardCollector(logger log.Logger, client *scw.Client, failures *prom
 	collector := &DashboardCollector{
 		client:   client,
 		instance: instance.NewAPI(client),
-		logger:   log.With(logger, "collector", "dashboard"),
+		logger:   logger.With("collector", "dashboard"),
 		failures: failures,
 		duration: duration,
 		config:   cfg,
@@ -209,8 +208,7 @@ func (c *DashboardCollector) Collect(ch chan<- prometheus.Metric) {
 		c.duration.WithLabelValues("dashboard").Observe(time.Since(now).Seconds())
 
 		if err != nil {
-			level.Error(c.logger).Log(
-				"msg", "Failed to fetch dashboard",
+			c.logger.Error("Failed to fetch dashboard",
 				"zone", zone,
 				"err", err,
 			)