77 lines
1.3 KiB
Go
77 lines
1.3 KiB
Go
package pubsub
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import (
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"encoding/json"
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"io"
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"os"
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"sync"
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)
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// JSONTracer is a tracer that writes events to a file, encoded in json.
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type JSONTracer struct {
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w io.WriteCloser
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ch chan struct{}
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mx sync.Mutex
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buf []interface{}
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}
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// NewJsonTracer creates a new JSON tracer writing to file.
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func NewJSONTracer(file string) (*JSONTracer, error) {
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return OpenJSONTracer(file, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
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}
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// OpenJsonTracer creates a new JSON tracer, with explicit control of OpenFile flags and permissions.
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func OpenJSONTracer(file string, flags int, perm os.FileMode) (*JSONTracer, error) {
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f, err := os.OpenFile(file, flags, perm)
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if err != nil {
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return nil, err
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}
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tr := &JSONTracer{w: f, ch: make(chan struct{}, 1)}
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go tr.doWrite()
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return tr, nil
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}
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func (t *JSONTracer) Trace(evt interface{}) {
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t.mx.Lock()
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t.buf = append(t.buf, evt)
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t.mx.Unlock()
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select {
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case t.ch <- struct{}{}:
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default:
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}
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}
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func (t *JSONTracer) Close() {
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close(t.ch)
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}
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func (t *JSONTracer) doWrite() {
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var buf []interface{}
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enc := json.NewEncoder(t.w)
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for {
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_, ok := <-t.ch
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t.mx.Lock()
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tmp := t.buf
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t.buf = buf[:0]
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buf = tmp
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t.mx.Unlock()
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for i, evt := range buf {
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err := enc.Encode(evt)
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if err != nil {
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log.Errorf("error writing event trace: %s", err.Error())
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}
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buf[i] = nil
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}
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if !ok {
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t.w.Close()
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return
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}
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}
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}
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