Implement v2 interface based on slog

v2/context.go

@@ -0,0 +1,65 @@
+/*
+ Copyright The containerd Authors.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+// Package log provides types and functions related to logging, passing
+// loggers through a context, and attaching context to the logger.
+//
+// This package uses [log/slog] as the logging backend. It provides an
+// [Entry] type for compatibility with code previously using logrus-style
+// logging, while delegating all output to slog.
+//
+// Log level, format, and handler configuration should be done directly
+// through [log/slog] using [slog.SetDefault] before using this package.
+package log
+
+import (
+	"context"
+	"log/slog"
+)
+
+// G is a shorthand for [GetLogger].
+//
+// We may want to define this locally to a package to get package tagged log
+// messages.
+var G = GetLogger
+
+// L is the default logger.
+var L = &Entry{}
+
+type loggerKey struct{}
+
+// WithLogger returns a new context with the provided logger. Use in
+// combination with logger.WithField(s) for great effect.
+func WithLogger(ctx context.Context, logger *Entry) context.Context {
+	e := &Entry{
+ logger: logger.logger,
+ attr: logger.attr,
+ ctx: ctx,
+	}
+	return context.WithValue(ctx, loggerKey{}, e)
+}
+
+// GetLogger retrieves the current logger from the context. If no logger is
+// available, the default logger is returned.
+func GetLogger(ctx context.Context) *Entry {
+	if logger := ctx.Value(loggerKey{}); logger != nil {
+ return logger.(*Entry)
+	}
+	return &Entry{
+ logger: slog.Default(),
+ ctx: ctx,
+	}
+}

v2/context_test.go

@@ -0,0 +1,98 @@
+/*
+ Copyright The containerd Authors.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package log
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"log/slog"
+	"testing"
+)
+
+func TestLoggerContext(t *testing.T) {
+	ctx := context.Background()
+	ctx = WithLogger(ctx, G(ctx).WithField("test", "one"))
+
+	e := GetLogger(ctx)
+	a := G(ctx)
+	if e != a {
+ t.Errorf("should be the same entry: %+v, %+v", e, a)
+	}
+}
+
+func TestWithFields(t *testing.T) {
+	var buf bytes.Buffer
+	logger := slog.New(slog.NewTextHandler(&buf, &slog.HandlerOptions{Level: slog.LevelDebug}))
+
+	ctx := context.Background()
+	ctx = WithLogger(ctx, &Entry{logger: logger, ctx: ctx})
+
+	l := G(ctx)
+	l = l.WithFields(Fields{"hello1": "world1"})
+	l = l.WithFields(map[string]any{"hello2": "world2"})
+	l.Info("test message")
+
+	output := buf.String()
+	for _, expected := range []string{"hello1=world1", "hello2=world2", "test message"} {
+ if !bytes.Contains([]byte(output), []byte(expected)) {
+ t.Errorf("expected output to contain %q, got: %s", expected, output)
+ }
+	}
+}
+
+func TestLogf(t *testing.T) {
+	var buf bytes.Buffer
+	logger := slog.New(slog.NewTextHandler(&buf, &slog.HandlerOptions{Level: LevelTrace}))
+
+	ctx := context.Background()
+	ctx = WithLogger(ctx, &Entry{logger: logger, ctx: ctx})
+
+	l := G(ctx)
+
+	l.Tracef("trace %s", "msg")
+	l.Debugf("debug %s", "msg")
+	l.Infof("info %s", "msg")
+	l.Warnf("warn %s", "msg")
+	l.Errorf("error %s", "msg")
+
+	output := buf.String()
+	for _, expected := range []string{"trace msg", "debug msg", "info msg", "warn msg", "error msg"} {
+ if !bytes.Contains([]byte(output), []byte(expected)) {
+ t.Errorf("expected output to contain %q, got: %s", expected, output)
+ }
+	}
+}
+
+func TestWithError(t *testing.T) {
+	var buf bytes.Buffer
+	logger := slog.New(slog.NewTextHandler(&buf, nil))
+
+	ctx := context.Background()
+	ctx = WithLogger(ctx, &Entry{logger: logger, ctx: ctx})
+
+	l := G(ctx).WithError(fmt.Errorf("test error"))
+	l.Info("something failed")
+
+	output := buf.String()
+	if !bytes.Contains([]byte(output), []byte("error")) {
+ t.Errorf("expected output to contain error field, got: %s", output)
+	}
+	if !bytes.Contains([]byte(output), []byte("test error")) {
+ t.Errorf("expected output to contain error message, got: %s", output)
+	}
+}

v2/entry.go

@@ -0,0 +1,159 @@
+/*
+ Copyright The containerd Authors.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package log
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+)
+
+// Entry is a logging entry. It contains all the fields passed with
+// [Entry.WithFields]. It's finally logged when Trace, Debug, Info, Warn,
+// or Error is called on it. These objects can be reused and passed around
+// as much as you wish to avoid field duplication.
+//
+// Entry is for close compatibility with logrus and containerd/log,
+// consider using slog directly for new packages.
+//
+// NOTE: while similar, this package is not compatible with logrus
+// or containerd/log. It should be compatible for most uses but
+// the interface is reduced and only supports slog capabilities.
+// Some notable differences:
+// - No Fatal or Panic levels, no equivalent in slog
+type Entry struct {
+	logger *slog.Logger
+
+	attr []slog.Attr
+
+	ctx context.Context
+}
+
+// Fields type to pass to "WithFields".
+type Fields = map[string]any
+
+// WithError adds an error as single field to the Entry.
+func (entry *Entry) WithError(err error) *Entry {
+	return entry.WithField("error", err)
+}
+
+// WithContext adds a context to the Entry.
+func (entry *Entry) WithContext(ctx context.Context) *Entry {
+	return &Entry{
+ logger: entry.logger,
+ attr: entry.attr,
+ ctx: ctx,
+	}
+}
+
+// WithField adds a single field to the Entry.
+func (entry *Entry) WithField(key string, value any) *Entry {
+	return entry.WithFields(Fields{key: value})
+}
+
+// WithFields adds a map of fields to the Entry.
+func (entry *Entry) WithFields(fields Fields) *Entry {
+	attr := make([]slog.Attr, len(entry.attr), len(entry.attr)+len(fields))
+	copy(attr, entry.attr)
+	for k, v := range fields {
+ attr = append(attr, slog.Any(k, v))
+	}
+	return &Entry{
+ logger: entry.logger,
+ attr: attr,
+ ctx: entry.ctx,
+	}
+}
+
+// Log logs a message at the given level.
+func (entry *Entry) Log(level slog.Level, msg string) {
+	logger := entry.logger
+	if logger == nil {
+ logger = slog.Default()
+	}
+	ctx := entry.ctx
+	if ctx == nil {
+ ctx = context.Background()
+	}
+	logger.LogAttrs(ctx, level, msg, entry.attr...)
+}
+
+// Logf logs a formatted message at the given level.
+func (entry *Entry) Logf(level slog.Level, format string, args ...any) {
+	logger := entry.logger
+	if logger == nil {
+ logger = slog.Default()
+	}
+	if !logger.Enabled(entry.ctx, level) {
+ return
+	}
+	ctx := entry.ctx
+	if ctx == nil {
+ ctx = context.Background()
+	}
+	logger.LogAttrs(ctx, level, fmt.Sprintf(format, args...), entry.attr...)
+}
+
+// Trace logs a message at trace level (slog.LevelDebug-4).
+func (entry *Entry) Trace(msg string) {
+	entry.Log(LevelTrace, msg)
+}
+
+// Tracef logs a formatted message at trace level.
+func (entry *Entry) Tracef(format string, args ...any) {
+	entry.Logf(LevelTrace, format, args...)
+}
+
+// Debug logs a message at debug level.
+func (entry *Entry) Debug(msg string) {
+	entry.Log(slog.LevelDebug, msg)
+}
+
+// Debugf logs a formatted message at debug level.
+func (entry *Entry) Debugf(format string, args ...any) {
+	entry.Logf(slog.LevelDebug, format, args...)
+}
+
+// Info logs a message at info level.
+func (entry *Entry) Info(msg string) {
+	entry.Log(slog.LevelInfo, msg)
+}
+
+// Infof logs a formatted message at info level.
+func (entry *Entry) Infof(format string, args ...any) {
+	entry.Logf(slog.LevelInfo, format, args...)
+}
+
+// Warn logs a message at warn level.
+func (entry *Entry) Warn(msg string) {
+	entry.Log(slog.LevelWarn, msg)
+}
+
+// Warnf logs a formatted message at warn level.
+func (entry *Entry) Warnf(format string, args ...any) {
+	entry.Logf(slog.LevelWarn, format, args...)
+}
+
+// Error logs a message at error level.
+func (entry *Entry) Error(msg string) {
+	entry.Log(slog.LevelError, msg)
+}
+
+// Errorf logs a formatted message at error level.
+func (entry *Entry) Errorf(format string, args ...any) {
+	entry.Logf(slog.LevelError, format, args...)
+}

v2/go.mod

@@ -0,0 +1,3 @@
+module github.com/containerd/log/v2
+
+go 1.24

v2/level.go

@@ -0,0 +1,52 @@
+/*
+ Copyright The containerd Authors.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package log
+
+import "log/slog"
+
+// Level is a logging level.
+type Level = slog.Level
+
+// Supported log levels. These correspond to slog levels, with additional
+// levels defined for trace, fatal, and panic for compatibility.
+const (
+	// LevelTrace designates finer-grained informational events than
+	// [slog.LevelDebug].
+	LevelTrace Level = slog.LevelDebug - 4
+
+	// LevelDebug level. Usually only enabled when debugging. Very verbose
+	// logging.
+	LevelDebug Level = slog.LevelDebug
+
+	// LevelInfo level. General operational entries about what's going on
+	// inside the application.
+	LevelInfo Level = slog.LevelInfo
+
+	// LevelWarn level. Non-critical entries that deserve eyes.
+	LevelWarn Level = slog.LevelWarn
+
+	// LevelError level. Logs errors that should definitely be noted.
+	LevelError Level = slog.LevelError
+
+	// LevelFatal level. Provided for compatibility; maps to
+	// slog.LevelError + 2.
+	LevelFatal Level = slog.LevelError + 2
+
+	// LevelPanic level. Provided for compatibility; maps to
+	// slog.LevelError + 4.
+	LevelPanic Level = slog.LevelError + 4
+)