bufpool.go

// bufPool is a pool of byte buffers meant to used when encoding JSON responses
// out to a client.
// giving this a try over:
// https://github.com/oxtoacart/bpool/blob/master/bufferpool.go
var bufPool = sync.Pool{
	New: func() interface{} {
		return new(bytes.Buffer)
	},
}

// writeJSON pulls a byte buffer from bufPool and encodes JSON to it. If there
// is an error, that is returned. Otherwise, the bytes are written out to the
// ResponseWriter.
func writeJSON(w http.ResponseWriter, data interface{}) error {
	buf, ok := bufPool.Get().(*bytes.Buffer)
	if !ok {
		http.Error(w, "Internal server error", http.StatusInternalServerError)
		return errors.New("could not get a buffer from bufPool")
	}
	defer func() {
		// throw away any buffers that are too large. Tweak this number based
		// off some median or 95th perc response size number once in real use.
		if buf.Cap() > 2048 {
			fmt.Println("buffer cap is over 2048. Tossing")
			return
		}
		buf.Reset()
		bufPool.Put(buf)
	}()

	if err := json.NewEncoder(buf).Encode(data); err != nil {
		http.Error(w, "Internal server error", http.StatusInternalServerError)
		return err
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)

	if _, err := w.Write(buf.Bytes()); err != nil {
		fmt.Println("error writing bytes", err)
		return err
	}

	return nil
}