Idiomatic golang net/http gzip transparent compression (works with Alice)

gzip.go

package main

import (
	"compress/gzip"
	"io"
	"net/http"
	"strings"
)

// Gzip Compression
type gzipResponseWriter struct {
	io.Writer
	http.ResponseWriter
}

func (w gzipResponseWriter) Write(b []byte) (int, error) {
	return w.Writer.Write(b)
}

func Gzip(handler http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
			handler.ServeHTTP(w, r)
			return
		}
		w.Header().Set("Content-Encoding", "gzip")
		gz := gzip.NewWriter(w)
		defer gz.Close()
		gzw := gzipResponseWriter{Writer: gz, ResponseWriter: w}
		handler.ServeHTTP(gzw, r)
	})
}

Missing return after line 23?

yes, that return seems to be missing ;)

Content negotiation is overrated. Make way for CONTENT DICTATORSHIP!

This gist is currently the second google result for "golang gzip http" and the first google result for some related terms.

About content-length

If your upstream writer sets Content-Length, this will result in the wrong (smaller) length being passed to the client. The middleware should remove any Content-Length header set by the upstream writer.

• This cannot be done in the Gzip() function since the handler hasn't been called yet.
• You could either overwrite WriteHeader, or, check if headers have been sent in the first call to Write and remove the Content-Length header then.
• Tracking state of this process necessitates converting from value receiver to pointer receiver.

About sync.Pool

Performance of regularly creating gzip writers is non-optimal. The gzip writer should be kept in a sync.Pool for reuse to minimise GC pressure.

I reached out to the owner of the gist to fix the update.

Is there any further example of this gzip compression that also using the sync.Pool as per @mappu said ?

Here's an updated version if anyone's interested: https://gist.github.com/CJEnright/bc2d8b8dc0c1389a9feeddb110f822d7

In the case of serving a file, would it be an option to look for an already compressed version of the file?

For max compression:

gzip.NewWriterLevel(w, gzip.BestCompression)

Content negotiation is overrated. Make way for CONTENT DICTATORSHIP!

Pure gold, was just seeking for a solution and found this 😄

Created a package for this: https://github.com/TelephoneTan/GoHTTPGzipServer