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logbuffer.go
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logbuffer.go
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// Copyright 2015-2018 trivago N.V.
//
// 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 logger
import (
"fmt"
"github.com/sirupsen/logrus"
"io"
"os"
)
// FallbackLogDevice defines the fallback destination for when _GOLLUM_ is unavailable / not used
var FallbackLogDevice = os.Stdout
// LogrusHookBuffer implements logrus.Hook and is used to pools log messages during startup
// when the desired log destination (_GOLLUM_ stream or fallbackLogDevice) is not yet available
// or known. During normal operation it relays messages to targetHook and/or targetWriter.
type LogrusHookBuffer struct {
targetHook logrus.Hook
targetWriter io.Writer
buffer []*logrus.Entry
}
// NewLogrusHookBuffer returns a LogrusHookBuffer instance
func NewLogrusHookBuffer() LogrusHookBuffer {
return LogrusHookBuffer{}
}
// Levels and Fire() implement the logrus.Hook interface
func (lhb *LogrusHookBuffer) Levels() []logrus.Level {
return logrus.AllLevels
}
// Fire and Levels() implement the logrus.Hook interface.
func (lhb *LogrusHookBuffer) Fire(logrusEntry *logrus.Entry) error {
if lhb.targetHook == nil && lhb.targetWriter == nil {
// Store entry in buffer and return
lhb.buffer = append(lhb.buffer, logrusEntry)
return nil
}
// Handle entry directly
return lhb.relayEntry(logrusEntry)
}
// SetTargetHook sets the logrus hook to whose .Fire() method messages should be relayed
func (lhb *LogrusHookBuffer) SetTargetHook(hook logrus.Hook) {
lhb.targetHook = hook
}
// SetTargetWriter sets the io.Writer where messages should be written
func (lhb *LogrusHookBuffer) SetTargetWriter(writer io.Writer) {
lhb.targetWriter = writer
}
// Purge sends stored messages to targetHook and/or targetWriter and empties the buffer.
func (lhb *LogrusHookBuffer) Purge() {
// Relay all stored entries
for _, entry := range lhb.buffer {
lhb.relayEntry(entry)
}
// Empty the buffer
lhb.buffer = []*logrus.Entry{}
}
// relayEntry relays one entry to the targetHook and/or writes it to targetWriter.
func (lhb *LogrusHookBuffer) relayEntry(entry *logrus.Entry) error {
// Relay entry to final hook
if lhb.targetHook != nil {
err := lhb.targetHook.Fire(entry)
if err != nil {
return err
}
}
// Relay entry to Writer
if lhb.targetWriter != nil {
serialized, err := entry.Logger.Formatter.Format(entry)
if err != nil {
_ = fmt.Errorf("failed to serialize log entry: %s", err.Error())
return err
}
_, err = lhb.targetWriter.Write(serialized)
if err != nil {
_ = fmt.Errorf("failed to write log entry %s: %s", serialized, err.Error())
return err
}
}
// Success
return nil
}