Use slog instead of logr

CHANGELOG.md

@@ -29,16 +29,32 @@ OpenTelemetry Go Automatic Instrumentation adheres to [Semantic Versioning](http
 - Add gRPC status code attribute for client spans (`rpc.grpc.status_code`). ([#1044](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1044))
 - Support `google.golang.org/grpc` `1.68.0-dev`. ([#1044](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1044))
 - Support `go.opentelemetry.io/otel@v1.30.0`. ([#1044](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1044))
+- The `WithLogger` `InstrumentationOption` is added as a replacement for `WithLogLevel`.
+  An `slog.Logger` can now be configured by the user any way they want and then passed to the `Instrumentation` for its logging with this option.
+  By default, if this is not provided, the default `slog` `Logger` will be used. ([#1080](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1080))
 
 ### Changed
 
 - The `WithSampler` option function now accepts the new `Sampler` interface instead of `trace.Sampler`. ([#982](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/982))
+- The `WithEnv` `InstrumentationOption` no longer supports the `OTEL_LOG_LEVEL` environment variable.
+  This is now configured by the user via the logger they pass using the added `WithLogger` option. ([#1080](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1080))
 
 ### Fixed
 
 - Fix dirty shutdown caused by panic. ([#980](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/980))
 - Flush pending span exports on shutdown. ([#1028](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1028))
 
+### Removed
+
+- `WithLogLevel` is removed.
+  Use `WithLogger` instead. ([#1080](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1080))
+- The unused `LogLevelDebug` constant is removed. ([#1080](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1080))
+- The unused `LogLevelInfo` constant is removed. ([#1080](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1080))
+- The unused `LogLevelWarn` constant is removed. ([#1080](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1080))
+- The unused `LogLevelError` constant is removed. ([#1080](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1080))
+- The unused `LogLevel` type is removed. ([#1080](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1080))
+- The unused `ParseLogLevel` function is removed. ([#1080](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/1080))
+
 ## [v0.14.0-alpha] - 2024-07-15
 
 ### Added

cli/main.go

@@ -8,26 +8,28 @@ import (
 	"errors"
 	"flag"
 	"fmt"
-	"log"
+	"log/slog"
 	"os"
 	"os/signal"
+	"path/filepath"
 	"syscall"
 
-	"github.com/go-logr/logr"
-	"github.com/go-logr/stdr"
-	"github.com/go-logr/zapr"
-	"go.uber.org/zap"
-
 	"go.opentelemetry.io/auto"
 	"go.opentelemetry.io/auto/internal/pkg/process"
 )
 
-const help = `
-OpenTelemetry auto-instrumentation for Go applications using eBPF
+const help = `Usage of %s:
+  -global-impl
+    	Record telemetry from the OpenTelemetry default global implementation
+  -log-level string
+    	logging level ("debug", "info", "warn", "error")
+
+Runs the OpenTelemetry auto-instrumentation for Go applications using eBPF.
 
 Environment variable configuration:
 
 	- OTEL_GO_AUTO_TARGET_EXE: sets the target binary
+	- OTEL_LOG_LEVEL: sets the log level (flag takes precedence)
 	- OTEL_SERVICE_NAME (or OTEL_RESOURCE_ATTRIBUTES): sets the service name
 	- OTEL_TRACES_EXPORTER: sets the trace exporter
 
@@ -37,19 +39,34 @@ package's documentation for information on supported values and registration of
 custom exporters.
 `
 
+// envLogLevelKey is the key for the environment variable value containing the
+// log level.
+const envLogLevelKey = "OTEL_LOG_LEVEL"
+
 func usage() {
-	fmt.Fprintf(os.Stderr, "%s", help)
+	program := filepath.Base(os.Args[0])
+	fmt.Fprintf(os.Stderr, help, program)
 }
 
-func newLogger() logr.Logger {
-	zapLog, err := zap.NewProduction()
+func newLogger(lvlStr string) *slog.Logger {
+	levelVar := new(slog.LevelVar) // Default value of info.
+	opts := &slog.HandlerOptions{AddSource: true, Level: levelVar}
+	h := slog.NewJSONHandler(os.Stderr, opts)
+	logger := slog.New(h)
 
-	var logger logr.Logger
-	if err != nil {
-		// Fallback to stdr logger.
-		logger = stdr.New(log.New(os.Stderr, "", log.LstdFlags))
+	if lvlStr == "" {
+		lvlStr = os.Getenv(envLogLevelKey)
+	}
+
+	if lvlStr == "" {
+		return logger
+	}
+
+	var level slog.Level
+	if err := level.UnmarshalText([]byte(lvlStr)); err != nil {
+		logger.Error("failed to parse log level", "error", err, "log-level", lvlStr)
 	} else {
-		logger = zapr.NewLogger(zapLog)
+		levelVar.Set(level)
 	}
 
 	return logger
@@ -60,12 +77,12 @@ func main() {
 	var logLevel string
 
 	flag.BoolVar(&globalImpl, "global-impl", false, "Record telemetry from the OpenTelemetry default global implementation")
-	flag.StringVar(&logLevel, "log-level", "", "Define log visibility level, default is `info`")
+	flag.StringVar(&logLevel, "log-level", "", `logging level ("debug", "info", "warn", "error")`)
 
 	flag.Usage = usage
 	flag.Parse()
 
-	logger := newLogger().WithName("go.opentelemetry.io/auto")
+	logger := newLogger(logLevel)
 
 	// Trap Ctrl+C and SIGTERM and call cancel on the context.
 	ctx, cancel := context.WithCancel(context.Background())
@@ -95,19 +112,9 @@ func main() {
 		instOptions = append(instOptions, auto.WithGlobal())
 	}
 
-	if logLevel != "" {
-		level, err := auto.ParseLogLevel(logLevel)
-		if err != nil {
-			logger.Error(err, "failed to parse log level")
-			return
-		}
-
-		instOptions = append(instOptions, auto.WithLogLevel(level))
-	}
-
 	inst, err := auto.NewInstrumentation(ctx, instOptions...)
 	if err != nil {
-		logger.Error(err, "failed to create instrumentation")
+		logger.Error("failed to create instrumentation", "error", err)
 		return
 	}
 
@@ -122,6 +129,6 @@ func main() {
 
 	logger.Info("starting instrumentation...")
 	if err = inst.Run(ctx); err != nil && !errors.Is(err, process.ErrInterrupted) {
-		logger.Error(err, "instrumentation crashed")
+		logger.Error("instrumentation crashed", "error", err)
 	}
 }