forked from TrueCloudLab/distribution
126 lines
3.5 KiB
Go
126 lines
3.5 KiB
Go
package logrustash
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import (
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"io"
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"sync"
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"github.com/sirupsen/logrus"
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)
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// Hook represents a Logstash hook.
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// It has two fields: writer to write the entry to Logstash and
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// formatter to format the entry to a Logstash format before sending.
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//
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// To initialize it use the `New` function.
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//
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type Hook struct {
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writer io.Writer
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formatter logrus.Formatter
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}
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// New returns a new logrus.Hook for Logstash.
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//
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// To create a new hook that sends logs to `tcp://logstash.corp.io:9999`:
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//
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// conn, _ := net.Dial("tcp", "logstash.corp.io:9999")
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// hook := logrustash.New(conn, logrustash.DefaultFormatter())
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func New(w io.Writer, f logrus.Formatter) logrus.Hook {
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return Hook{
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writer: w,
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formatter: f,
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}
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}
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// Fire takes, formats and sends the entry to Logstash.
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// Hook's formatter is used to format the entry into Logstash format
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// and Hook's writer is used to write the formatted entry to the Logstash instance.
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func (h Hook) Fire(e *logrus.Entry) error {
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dataBytes, err := h.formatter.Format(e)
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if err != nil {
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return err
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}
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_, err = h.writer.Write(dataBytes)
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return err
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}
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// Levels returns all logrus levels.
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func (h Hook) Levels() []logrus.Level {
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return logrus.AllLevels
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}
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// Using a pool to re-use of old entries when formatting Logstash messages.
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// It is used in the Fire function.
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var entryPool = sync.Pool{
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New: func() interface{} {
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return &logrus.Entry{}
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},
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}
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// copyEntry copies the entry `e` to a new entry and then adds all the fields in `fields` that are missing in the new entry data.
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// It uses `entryPool` to re-use allocated entries.
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func copyEntry(e *logrus.Entry, fields logrus.Fields) *logrus.Entry {
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ne := entryPool.Get().(*logrus.Entry)
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ne.Message = e.Message
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ne.Level = e.Level
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ne.Time = e.Time
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ne.Data = logrus.Fields{}
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for k, v := range fields {
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ne.Data[k] = v
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}
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for k, v := range e.Data {
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ne.Data[k] = v
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}
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return ne
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}
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// releaseEntry puts the given entry back to `entryPool`. It must be called if copyEntry is called.
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func releaseEntry(e *logrus.Entry) {
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entryPool.Put(e)
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}
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// LogstashFormatter represents a Logstash format.
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// It has logrus.Formatter which formats the entry and logrus.Fields which
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// are added to the JSON message if not given in the entry data.
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//
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// Note: use the `DefaultFormatter` function to set a default Logstash formatter.
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type LogstashFormatter struct {
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logrus.Formatter
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logrus.Fields
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}
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var (
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logstashFields = logrus.Fields{"@version": "1", "type": "log"}
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logstashFieldMap = logrus.FieldMap{
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logrus.FieldKeyTime: "@timestamp",
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logrus.FieldKeyMsg: "message",
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}
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)
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// DefaultFormatter returns a default Logstash formatter:
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// A JSON format with "@version" set to "1" (unless set differently in `fields`,
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// "type" to "log" (unless set differently in `fields`),
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// "@timestamp" to the log time and "message" to the log message.
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//
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// Note: to set a different configuration use the `LogstashFormatter` structure.
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func DefaultFormatter(fields logrus.Fields) logrus.Formatter {
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for k, v := range logstashFields {
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if _, ok := fields[k]; !ok {
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fields[k] = v
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}
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}
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return LogstashFormatter{
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Formatter: &logrus.JSONFormatter{FieldMap: logstashFieldMap},
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Fields: fields,
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}
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}
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// Format formats an entry to a Logstash format according to the given Formatter and Fields.
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//
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// Note: the given entry is copied and not changed during the formatting process.
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func (f LogstashFormatter) Format(e *logrus.Entry) ([]byte, error) {
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ne := copyEntry(e, f.Fields)
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dataBytes, err := f.Formatter.Format(ne)
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releaseEntry(ne)
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return dataBytes, err
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}
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