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/prometheus-hetzner-sd/issues/270

pkg/action/discoverer.go

@@ -3,13 +3,12 @@ package action
 import (
 	"context"
 	"fmt"
+	"log/slog"
 	"strconv"
 	"strings"
 	"time"
 
 	"github.com/appscode/go-hetzner"
-	"github.com/go-kit/log"
-	"github.com/go-kit/log/level"
 	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/discovery/targetgroup"
 )
@@ -37,7 +36,7 @@ var (
 // Discoverer implements the Prometheus discoverer interface.
 type Discoverer struct {
 	clients map[string]*hetzner.Client
-	logger  log.Logger
+	logger  *slog.Logger
 	refresh int
 	lasts   map[string]struct{}
 }
@@ -72,8 +71,7 @@ func (d *Discoverer) getTargets(_ context.Context) ([]*targetgroup.Group, error)
 		requestDuration.WithLabelValues(project).Observe(time.Since(now).Seconds())
 
 		if err != nil {
-			level.Warn(d.logger).Log(
-				"msg", "Failed to fetch servers",
+			d.logger.Warn("Failed to fetch servers",
 				"project", project,
 				"err", err,
 			)
@@ -82,8 +80,7 @@ func (d *Discoverer) getTargets(_ context.Context) ([]*targetgroup.Group, error)
 			continue
 		}
 
-		level.Debug(d.logger).Log(
-			"msg", "Requested servers",
+		d.logger.Debug("Requested servers",
 			"project", project,
 			"count", len(servers),
 		)
@@ -112,8 +109,7 @@ func (d *Discoverer) getTargets(_ context.Context) ([]*targetgroup.Group, error)
 				},
 			}
 
-			level.Debug(d.logger).Log(
-				"msg", "Server added",
+			d.logger.Debug("Server added",
 				"project", project,
 				"source", target.Source,
 			)
@@ -126,8 +122,7 @@ func (d *Discoverer) getTargets(_ context.Context) ([]*targetgroup.Group, error)
 
 	for k := range d.lasts {
 		if _, ok := current[k]; !ok {
-			level.Debug(d.logger).Log(
-				"msg", "Server deleted",
+			d.logger.Debug("Server deleted",
 				"source", k,
 			)
 

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/prometheus-hetzner-sd/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

@@ -4,15 +4,14 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"log/slog"
 	"net/http"
 	"os"
 	"os/signal"
 	"time"
 
 	"github.com/appscode/go-hetzner"
 	"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 Prometheus Hetzner SD",
+func Server(cfg *config.Config, logger *slog.Logger) error {
+	logger.Info("Launching Prometheus Hetzner SD",
 		"version", version.String,
 		"revision", version.Revision,
 		"date", version.Date,
@@ -43,8 +41,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 			username, err := config.Value(credential.Username)
 
 			if err != nil {
-				level.Error(logger).Log(
-					"msg", "Failed to read username secret",
+				logger.Error("Failed to read username secret",
 					"project", credential.Project,
 					"err", err,
 				)
@@ -55,8 +52,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 			password, err := config.Value(credential.Password)
 
 			if err != nil {
-				level.Error(logger).Log(
-					"msg", "Failed to read password secret",
+				logger.Error("Failed to read password secret",
 					"project", credential.Project,
 					"err", err,
 				)
@@ -90,9 +86,8 @@ 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(
@@ -109,16 +104,14 @@ 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,
 			)
 		})
@@ -141,7 +134,7 @@ func Server(cfg *config.Config, logger log.Logger) error {
 	return gr.Run()
 }
 
-func handler(cfg *config.Config, logger log.Logger) *chi.Mux {
+func handler(cfg *config.Config, logger *slog.Logger) *chi.Mux {
 	mux := chi.NewRouter()
 	mux.Use(middleware.Recoverer(logger))
 	mux.Use(middleware.RealIP)
@@ -181,8 +174,7 @@ func handler(cfg *config.Config, logger log.Logger) *chi.Mux {
 				content, err := os.ReadFile(cfg.Target.File)
 
 				if err != nil {
-					level.Info(logger).Log(
-						"msg", "Failed to read service discovery data",
+					logger.Error("Failed to read service discovery data",
 						"err", err,
 					)
 

pkg/adapter/adapter.go

@@ -19,12 +19,11 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"log/slog"
 	"os"
 	"path/filepath"
 	"reflect"
 
-	"github.com/go-kit/log"
-	"github.com/go-kit/log/level"
 	"github.com/prometheus/prometheus/discovery"
 	"github.com/prometheus/prometheus/discovery/targetgroup"
 )
@@ -43,7 +42,7 @@ type Adapter struct {
 	manager *discovery.Manager
 	output  string
 	name    string
-	logger  log.Logger
+	logger  *slog.Logger
 }
 
 func mapToArray(m map[string]*customSD) []customSD {
@@ -84,7 +83,7 @@ func (a *Adapter) generateTargetGroups(allTargetGroups map[string][]*targetgroup
 		a.groups = tempGroups
 		err := a.writeOutput()
 		if err != nil {
-			level.Error(log.With(a.logger, "component", "sd-adapter")).Log("err", err)
+			a.logger.With("component", "sd-adapter").Error("", "err", err)
 		}
 	}
 
@@ -138,12 +137,12 @@ func (a *Adapter) Run() {
 }
 
 // NewAdapter creates a new instance of Adapter.
-func NewAdapter(ctx context.Context, file string, name string, d discovery.Discoverer, logger log.Logger) *Adapter {
+func NewAdapter(ctx context.Context, file string, name string, d discovery.Discoverer, logger *slog.Logger) *Adapter {
 	return &Adapter{
 		ctx:     ctx,
 		disc:    d,
 		groups:  make(map[string]*customSD),
-		manager: discovery.NewManager(ctx, logger),
+		manager: discovery.NewManager(ctx, nil),
 		output:  file,
 		name:    name,
 		logger:  logger,

pkg/command/health.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 	"net/http"
 
-	"github.com/go-kit/log/level"
 	"github.com/promhippie/prometheus-hetzner-sd/pkg/config"
 	"github.com/urfave/cli/v2"
 )
@@ -20,8 +19,7 @@ func Health(cfg *config.Config) *cli.Command {
 
 			if c.IsSet("hetzner.config") {
 				if err := readConfig(c.String("hetzner.config"), cfg); err != nil {
-					level.Error(logger).Log(
-						"msg", "Failed to read config",
+					logger.Error("Failed to read config",
 						"err", err,
 					)
 
@@ -37,8 +35,7 @@ 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,
 				)
 
@@ -48,15 +45,18 @@ 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/server.go

@@ -3,7 +3,6 @@ package command
 import (
 	"errors"
 
-	"github.com/go-kit/log/level"
 	"github.com/promhippie/prometheus-hetzner-sd/pkg/action"
 	"github.com/promhippie/prometheus-hetzner-sd/pkg/config"
 	"github.com/urfave/cli/v2"
@@ -20,8 +19,7 @@ func Server(cfg *config.Config) *cli.Command {
 
 			if c.IsSet("hetzner.config") {
 				if err := readConfig(c.String("hetzner.config"), cfg); err != nil {
-					level.Error(logger).Log(
-						"msg", "Failed to read config",
+					logger.Error("Failed to read config",
 						"err", err,
 					)
 
@@ -30,10 +28,7 @@ func Server(cfg *config.Config) *cli.Command {
 			}
 
 			if cfg.Target.File == "" {
-				level.Error(logger).Log(
-					"msg", "Missing path for output.file",
-				)
-
+				logger.Error("Missing path for output.file")
 				return errors.New("missing path for output.file")
 			}
 
@@ -50,27 +45,18 @@ func Server(cfg *config.Config) *cli.Command {
 				)
 
 				if credentials.Username == "" {
-					level.Error(logger).Log(
-						"msg", "Missing required hetzner.username",
-					)
-
+					logger.Error("Missing required hetzner.username")
 					return errors.New("missing required hetzner.username")
 				}
 
 				if credentials.Password == "" {
-					level.Error(logger).Log(
-						"msg", "Missing required hetzner.password",
-					)
-
+					logger.Error("Missing required hetzner.password")
 					return errors.New("missing required hetzner.password")
 				}
 			}
 
 			if len(cfg.Target.Credentials) == 0 {
-				level.Error(logger).Log(
-					"msg", "Missing any credentials",
-				)
-
+				logger.Error("Missing any credentials")
 				return errors.New("missing any credentials")
 			}