func (m *Middleware) ServeHTTP(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
start := time.Now()
next(rw, r)
res := negroni.NewResponseWriter(rw)
m.reqs.WithLabelValues(http.StatusText(res.Status()), r.Method, r.URL.Path).Inc()
m.latency.WithLabelValues(http.StatusText(res.Status()), r.Method, r.URL.Path).Observe(float64(time.Since(start).Nanoseconds()) / 1000000)
}
// ServeHTTP wraps the http.ResponseWriter with a gzip.Writer.
func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
// Skip compression if the client doesn't accept gzip encoding.
if !strings.Contains(r.Header.Get(headerAcceptEncoding), encodingGzip) {
next(w, r)
return
}
// Skip compression if client attempt WebSocket connection
if len(r.Header.Get(headerSecWebSocketKey)) > 0 {
next(w, r)
return
}
// Skip compression if already compressed
if w.Header().Get(headerContentEncoding) == encodingGzip {
next(w, r)
return
}
// Retrieve gzip writer from the pool. Reset it to use the ResponseWriter.
// This allows us to re-use an already allocated buffer rather than
// allocating a new buffer for every request.
// We defer g.pool.Put here so that the gz writer is returned to the
// pool if any thing after here fails for some reason (functions in
// next could potentially panic, etc)
gz := h.pool.Get().(*gzip.Writer)
defer h.pool.Put(gz)
gz.Reset(w)
// Set the appropriate gzip headers.
headers := w.Header()
headers.Set(headerContentEncoding, encodingGzip)
headers.Set(headerVary, headerAcceptEncoding)
// Wrap the original http.ResponseWriter with negroni.ResponseWriter
// and create the gzipResponseWriter.
nrw := negroni.NewResponseWriter(w)
grw := gzipResponseWriter{
gz,
nrw,
}
// Call the next handler supplying the gzipResponseWriter instead of
// the original.
next(grw, r)
// Delete the content length after we know we have been written to.
grw.Header().Del(headerContentLength)
gz.Close()
}