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)
	})
}

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