Provide contexted logger instance as public package

xiekeyang · xiekeyang · commit 548a4ae124f9 · 2017-03-14T14:56:59.000+08:00
The logger instance, exported from logrus, is retrived through context
value. It helps image tools to print out arbitrarily information.
Besides that, it fires the output to I/O devices like stdout and stderr.

Signed-off-by: xiekeyang &lt;xiekeyang@huawei.com&gt;
diff --git a/context/context.go b/context/context.go
@@ -0,0 +1,31 @@
+// Copyright 2016 The Linux Foundation
+//
+// 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 context
+
+import (
+	"golang.org/x/net/context"
+)
+
+// Context is a copy of Context from the golang.org/x/net/context package.
+type Context interface {
+	context.Context
+}
+
+// Background returns a non-nil, empty Context. The background context
+// provides a single key, "instance.id" that is globally unique to the
+// process.
+func Background() context.Context {
+	return context.Background()
+}
diff --git a/context/logger.go b/context/logger.go
@@ -0,0 +1,101 @@
+// Copyright 2016 The Linux Foundation
+//
+// 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 context
+
+import (
+	"fmt"
+	"os"
+	"reflect"
+
+	"github.com/Sirupsen/logrus"
+	"golang.org/x/net/context"
+)
+
+var (
+	// G is an alias for GetLogger.
+	//
+	// We may want to define this locally to a package to get package tagged log
+	// messages.
+	G = GetLogger
+
+	// LogEntry provides a public and standard logger instance.
+	LogEntry = logrus.NewEntry(logrus.StandardLogger())
+)
+
+type (
+	loggerKey struct{}
+
+	stderrHook struct{}
+)
+
+// Levels provide the method for logrus.Hook interface
+func (h *stderrHook) Levels() []logrus.Level {
+	return []logrus.Level{
+		logrus.PanicLevel,
+		logrus.FatalLevel,
+		logrus.ErrorLevel,
+		logrus.WarnLevel,
+	}
+}
+
+// Fire provide the method for logrus.Hook interface
+func (h *stderrHook) Fire(entry *logrus.Entry) error {
+	log := reflect.ValueOf(*entry.Logger).Interface().(logrus.Logger)
+	entry.Logger = &log
+	entry.Logger.Out = os.Stderr
+	return nil
+}
+
+// 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 *logrus.Entry) context.Context {
+	return context.WithValue(ctx, loggerKey{}, logger)
+}
+
+// GetLogger retrieves the current logger from the context. If no logger is
+// available, the default logger is returned.
+func GetLogger(ctx context.Context) *logrus.Entry {
+	logger := ctx.Value(loggerKey{})
+
+	if logger == nil {
+		return LogEntry
+	}
+
+	return logger.(*logrus.Entry)
+}
+
+// EnableDebugMode enables a selectable debug mode.
+func EnableDebugMode(debug bool) error {
+	var level string
+	if LogEntry == nil {
+		return fmt.Errorf("logger entry instance not found")
+	}
+	if debug {
+		level = "debug"
+	} else {
+		level = "info"
+	}
+	lvl, err := logrus.ParseLevel(level)
+	if err != nil {
+		return err
+	}
+	LogEntry.Logger.Level = lvl
+	return nil
+}
+
+func init() {
+	LogEntry.Logger.Out = os.Stdout
+	LogEntry.Logger.Hooks.Add(&stderrHook{})
+}
