@@ -72,17 +72,17 @@ func run(ctx context.Context, router Router, analyticsFile string) error {
		if err != nil {
			return err
		}
	}

	server := &http.Server{Addr: *httpFlag, Handler: top{&errorHandler{handler: (&handler{
	server := &http.Server{Addr: *httpFlag, Handler: top{gzipHandler{&errorHandler{handler: (&handler{
		rtr:           router,
		analyticsHTML: analyticsHTML,
		fontsHandler:  httpgzip.FileServer(assets.Fonts, httpgzip.FileServerOptions{ServeError: httpgzip.Detailed}),
		assetsHandler: httpgzip.FileServer(assets.Assets, httpgzip.FileServerOptions{ServeError: httpgzip.Detailed}),
		s:             newService(ctx),
	}).ServeHTTP}}}
	}).ServeHTTP}}}}

	go func() {
		<-ctx.Done()
		err := server.Close()
		if err != nil {

@@ -1,19 +1,22 @@
package main

import (
	"compress/gzip"
	"context"
	"errors"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"os"
	"time"

	"github.com/shurcooL/httperror"
	"github.com/shurcooL/users"
	"golang.org/x/net/http/httpguts"
)

// errorHandler factors error handling out of the HTTP handler.
type errorHandler struct {
	handler func(w http.ResponseWriter, req *http.Request) error
@@ -105,10 +108,80 @@ func (rw *headerResponseWriter) Write(p []byte) (n int, err error) {
func (rw *headerResponseWriter) WriteHeader(code int) {
	rw.WroteHeader = true
	rw.ResponseWriter.WriteHeader(code)
}

// gzipHandler applies gzip compression on top of Handler, unless Handler
// has already handled it (i.e., the "Content-Encoding" header is set).
type gzipHandler struct {
	Handler http.Handler
}

func (h gzipHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	// If request doesn't accept gzip encoding, serve without compression.
	if !httpguts.HeaderValuesContainsToken(req.Header["Accept-Encoding"], "gzip") {
		h.Handler.ServeHTTP(w, req)
		return
	}

	// Otherwise, use gzipResponseWriter to start gzip compression when WriteHeader
	// is called, but only if the handler didn't already take care of it.
	rw := &gzipResponseWriter{ResponseWriter: w}
	defer rw.Close()
	h.Handler.ServeHTTP(rw, req)
}

// gzipHandler starts gzip compression when WriteHeader is called, unless compression
// has already been applied by that time (i.e., the "Content-Encoding" header is set).
type gzipResponseWriter struct {
	http.ResponseWriter

	// These fields are set by setWriterAndCloser
	// during first call to Write or WriteHeader.
	w io.Writer // When set, must be non-nil.
	c io.Closer // May be nil.
}

func (rw *gzipResponseWriter) WriteHeader(code int) {
	if rw.w != nil {
		panic(fmt.Errorf("internal error: gzipResponseWriter: WriteHeader called twice or after Write"))
	}
	rw.setWriterAndCloser()
	rw.ResponseWriter.WriteHeader(code)
}
func (rw *gzipResponseWriter) Write(p []byte) (n int, err error) {
	if rw.w == nil {
		rw.setWriterAndCloser()
	}
	return rw.w.Write(p)
}

func (rw *gzipResponseWriter) setWriterAndCloser() {
	if _, ok := rw.Header()["Content-Encoding"]; ok {
		// Compression already handled by the handler.
		rw.w = rw.ResponseWriter
		return
	}

	// Update headers, start using a gzip writer.
	rw.Header().Set("Content-Encoding", "gzip")
	rw.Header().Del("Content-Length")
	gw := gzip.NewWriter(rw.ResponseWriter)
	rw.w = gw
	rw.c = gw
}

func (rw *gzipResponseWriter) Close() {
	if rw.c == nil {
		return
	}
	err := rw.c.Close()
	if err != nil {
		log.Printf("gzipResponseWriter.Close: error closing *gzip.Writer: %v", err)
	}
}

// top adds some instrumentation on top of Handler.
type top struct{ Handler http.Handler }

func (t top) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	path := req.URL.Path