routesrv: accept gzip encoding

Support gzip encoding to reduce response size.

Signed-off-by: Alexander Yastrebov <[email protected]>

routesrv/eskipbytes.go

@@ -2,10 +2,12 @@ package routesrv
 
 import (
 	"bytes"
+	"compress/gzip"
 	"crypto/sha256"
 	"fmt"
 	"net/http"
 	"strconv"
+	"strings"
 	"sync"
 	"time"
 
@@ -50,12 +52,15 @@ var (
 // provides synchronized r/w access to them. Additionally it can
 // serve as an HTTP handler exposing its content.
 type eskipBytes struct {
+	mu           sync.RWMutex
 	data         []byte
-	etag         string
+	hash         string
 	lastModified time.Time
 	initialized  bool
 	count        int
-	mu           sync.RWMutex
+
+	zw    *gzip.Writer
+	zdata []byte
 
 	tracer  ot.Tracer
 	metrics metrics.Metrics
@@ -77,13 +82,33 @@ func (e *eskipBytes) formatAndSet(routes []*eskip.Route) (_ int, _ string, initi
 	if updated {
 		e.lastModified = e.now()
 		e.data = data
-		e.etag = fmt.Sprintf(`"%x"`, sha256.Sum256(e.data))
+		e.zdata = e.compressLocked(data)
+		e.hash = fmt.Sprintf("%x", sha256.Sum256(e.data))
 		e.count = len(routes)
 	}
 	initialized = !e.initialized
 	e.initialized = true
 
-	return len(e.data), e.etag, initialized, updated
+	return len(e.data), e.hash, initialized, updated
+}
+
+// compressLocked compresses the data with gzip and returns
+// the compressed data or nil if compression fails.
+// e.mu must be held.
+func (e *eskipBytes) compressLocked(data []byte) []byte {
+	var buf bytes.Buffer
+	if e.zw == nil {
+		e.zw = gzip.NewWriter(&buf)
+	} else {
+		e.zw.Reset(&buf)
+	}
+	if _, err := e.zw.Write(data); err != nil {
+		return nil
+	}
+	if err := e.zw.Close(); err != nil {
+		return nil
+	}
+	return buf.Bytes()
 }
 
 func (e *eskipBytes) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
@@ -112,17 +137,24 @@ func (e *eskipBytes) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 	e.mu.RLock()
 	count := e.count
 	data := e.data
-	etag := e.etag
+	zdata := e.zdata
+	hash := e.hash
 	lastModified := e.lastModified
 	initialized := e.initialized
 	e.mu.RUnlock()
 
 	if initialized {
-		w.Header().Add("Etag", etag)
-		w.Header().Add("Content-Type", "text/plain; charset=utf-8")
-		w.Header().Add(routing.RoutesCountName, strconv.Itoa(count))
-
-		http.ServeContent(w, r, "", lastModified, bytes.NewReader(data))
+		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		w.Header().Set(routing.RoutesCountName, strconv.Itoa(count))
+
+		if strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") && len(zdata) > 0 {
+			w.Header().Set("Etag", `"`+hash+`+gzip"`)
+			w.Header().Set("Content-Encoding", "gzip")
+			http.ServeContent(w, r, "", lastModified, bytes.NewReader(zdata))
+		} else {
+			w.Header().Set("Etag", `"`+hash+`"`)
+			http.ServeContent(w, r, "", lastModified, bytes.NewReader(data))
+		}
 	} else {
 		w.WriteHeader(http.StatusNotFound)
 	}

routesrv/polling.go

@@ -78,8 +78,8 @@ func (p *poller) poll(wg *sync.WaitGroup) {
 				"message", LogRoutesEmpty,
 			)
 		case routesCount > 0:
-			routesBytes, routesEtag, initialized, updated := p.b.formatAndSet(routes)
-			logger := log.WithFields(log.Fields{"count": routesCount, "bytes": routesBytes, "etag": routesEtag})
+			routesBytes, routesHash, initialized, updated := p.b.formatAndSet(routes)
+			logger := log.WithFields(log.Fields{"count": routesCount, "bytes": routesBytes, "hash": routesHash})
 			if initialized {
 				logger.Info(LogRoutesInitialized)
 				span.SetTag("routes.initialized", true)
@@ -94,7 +94,7 @@ func (p *poller) poll(wg *sync.WaitGroup) {
 			}
 			span.SetTag("routes.count", routesCount)
 			span.SetTag("routes.bytes", routesBytes)
-			span.SetTag("routes.etag", routesEtag)
+			span.SetTag("routes.hash", routesHash)
 
 			if updated && log.IsLevelEnabled(log.DebugLevel) {
 				routesById := mapRoutes(routes)

routesrv/routesrv_test.go

@@ -2,6 +2,7 @@ package routesrv_test
 
 import (
 	"bytes"
+	"compress/gzip"
 	"flag"
 	"io"
 	"net/http"
@@ -16,6 +17,7 @@ import (
 	"github.com/google/go-cmp/cmp"
 	"github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"github.com/zalando/skipper"
 	"github.com/zalando/skipper/dataclients/kubernetes/kubernetestest"
@@ -724,3 +726,59 @@ func TestRoutesWithExplicitLBAlgorithm(t *testing.T) {
 	}
 	wantHTTPCode(t, responseRecorder, http.StatusOK)
 }
+
+func TestESkipBytesHandlerGzip(t *testing.T) {
+	defer tl.Reset()
+	ks, handler := newKubeServer(t, loadKubeYAML(t, "testdata/lb-target-multi.yaml"))
+	ks.Start()
+	defer ks.Close()
+	rs := newRouteServer(t, ks)
+
+	rs.StartUpdates()
+	defer rs.StopUpdates()
+
+	testGzipResponse := func(t *testing.T, routes int) {
+		// Get plain response
+		plainResponse := getRoutes(rs)
+		plainEtag := plainResponse.Header().Get("Etag")
+		plainContent := plainResponse.Body.Bytes()
+
+		// Get gzip response
+		gzipResponse := getRoutesWithRequestHeadersSetting(rs, map[string]string{"Accept-Encoding": "gzip"})
+		assert.Equal(t, http.StatusOK, gzipResponse.Code)
+		assert.Equal(t, "text/plain; charset=utf-8", gzipResponse.Header().Get("Content-Type"))
+		assert.Equal(t, "gzip", gzipResponse.Header().Get("Content-Encoding"))
+		assert.Equal(t, strconv.Itoa(routes), gzipResponse.Header().Get("X-Count"))
+
+		gzipEtag := gzipResponse.Header().Get("Etag")
+		assert.NotEqual(t, plainEtag, gzipEtag, "gzip Etag should differ from plain Etag")
+
+		zr, err := gzip.NewReader(gzipResponse.Body)
+		require.NoError(t, err)
+		defer zr.Close()
+
+		gzipContent, err := io.ReadAll(zr)
+		require.NoError(t, err)
+
+		assert.Equal(t, plainContent, gzipContent, "gzip content should be equal to plain content")
+
+		// Get gzip response using Etag
+		gzipEtagResponse := getRoutesWithRequestHeadersSetting(rs, map[string]string{"If-None-Match": gzipEtag, "Accept-Encoding": "gzip"})
+
+		assert.Equal(t, http.StatusNotModified, gzipEtagResponse.Code)
+		// RFC 7232 section 4.1:
+		assert.Empty(t, gzipEtagResponse.Header().Get("Content-Type"))
+		assert.Empty(t, gzipEtagResponse.Header().Get("Content-Length"))
+		assert.Empty(t, gzipEtagResponse.Header().Get("Content-Encoding"))
+		assert.Equal(t, strconv.Itoa(routes), gzipEtagResponse.Header().Get("X-Count"))
+		assert.Empty(t, gzipEtagResponse.Body.String())
+	}
+
+	require.NoError(t, tl.WaitFor(routesrv.LogRoutesInitialized, waitTimeout))
+	testGzipResponse(t, 3)
+
+	handler.set(newKubeAPI(t, loadKubeYAML(t, "testdata/lb-target-single.yaml")))
+	require.NoError(t, tl.WaitForN(routesrv.LogRoutesUpdated, 2, waitTimeout))
+
+	testGzipResponse(t, 2)
+}