Automatically gzip responses

go.mod

@@ -3,6 +3,7 @@ module github.com/letsencrypt/ctile
 go 1.20
 
 require (
+	github.com/NYTimes/gziphandler v1.1.1
 	github.com/aws/aws-sdk-go-v2 v1.21.0
 	github.com/aws/aws-sdk-go-v2/config v1.18.37
 	github.com/aws/aws-sdk-go-v2/credentials v1.13.35

go.sum

@@ -1,3 +1,5 @@
+github.com/NYTimes/gziphandler v1.1.1 h1:ZUDjpQae29j0ryrS0u/B8HZfJBtBQHjqw2rQ2cqUQ3I=
+github.com/NYTimes/gziphandler v1.1.1/go.mod h1:n/CVRwUEOgIxrgPvAQhUUr9oeUtvrhMomdKFjzJNB0c=
 github.com/aws/aws-sdk-go-v2 v1.21.0 h1:gMT0IW+03wtYJhRqTVYn0wLzwdnK9sRMcxmtfGzRdJc=
 github.com/aws/aws-sdk-go-v2 v1.21.0/go.mod h1:/RfNgGmRxI+iFOB1OeJUyxiU+9s88k3pfHvDagGEp0M=
 github.com/aws/aws-sdk-go-v2/aws/protocol/eventstream v1.4.13 h1:OPLEkmhXf6xFPiz0bLeDArZIDx1NNS4oJyG4nv3Gct0=
@@ -55,6 +57,7 @@ github.com/jmespath/go-jmespath v0.4.0/go.mod h1:T8mJZnbsbmF+m6zOOFylbeCJqk5+pHW
 github.com/jmespath/go-jmespath/internal/testify v1.5.1/go.mod h1:L3OGu8Wl2/fWfCI6z80xFu9LTZmf1ZRjMHUOPmWr69U=
 github.com/matttproud/golang_protobuf_extensions v1.0.4 h1:mmDVorXM7PCGKw94cs5zkfA9PSy5pEvNWRP0ET0TIVo=
 github.com/matttproud/golang_protobuf_extensions v1.0.4/go.mod h1:BSXmuO+STAnVfrANrmjBb36TMTDstsz7MSK+HVaYKv4=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_golang v1.16.0 h1:yk/hx9hDbrGHovbci4BY+pRMfSuuat626eFsHb7tmT8=
 github.com/prometheus/client_golang v1.16.0/go.mod h1:Zsulrv/L9oM40tJ7T815tM89lFEugiJ9HzIqaAx4LKc=
@@ -65,6 +68,8 @@ github.com/prometheus/common v0.42.0/go.mod h1:xBwqVerjNdUDjgODMpudtOMwlOwf2SaTr
 github.com/prometheus/procfs v0.10.1 h1:kYK1Va/YMlutzCGazswoHKo//tZVlFpKYh+PymziUAg=
 github.com/prometheus/procfs v0.10.1/go.mod h1:nwNm2aOCAYw8uTR/9bWRREkZFxAUcWzPHWJq+XBB/FM=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=
 github.com/x448/float16 v0.8.4 h1:qLwI1I70+NjRFUR3zs1JPUCgaCXSh3SW62uAKT1mSBM=
 github.com/x448/float16 v0.8.4/go.mod h1:14CWIYCyZA/cWjXOioeEpHeN/83MdbZDRQHoFcYsOfg=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
@@ -79,3 +84,4 @@ google.golang.org/protobuf v1.30.0 h1:kPPoIgf3TsEvrm0PFe15JQ+570QVxYzEvvHqChK+cn
 google.golang.org/protobuf v1.30.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

integration_test.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"compress/gzip"
 	"context"
 	"encoding/binary"
 	"encoding/json"
@@ -275,7 +276,11 @@ func TestIntegration(t *testing.T) {
 	if resp.StatusCode != 400 {
 		t.Errorf("expected 400 got %d", resp.StatusCode)
 	}
-	body, _ := io.ReadAll(resp.Body)
+	gzReader, err := gzip.NewReader(resp.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	body, _ := io.ReadAll(gzReader)
 	if !strings.Contains(string(body), testLogSaysPastTheEnd) {
 		t.Errorf("expected response to contain %q got %q", testLogSaysPastTheEnd, body)
 	}
@@ -310,6 +315,7 @@ func TestIntegration(t *testing.T) {
 
 func getResp(ctile *tileCachingHandler, url string) *http.Response {
 	req := httptest.NewRequest("GET", url, nil)
+	req.Header.Set("Accept-Encoding", "gzip")
 	w := httptest.NewRecorder()
 
 	ctile.ServeHTTP(w, req)
@@ -324,8 +330,20 @@ func getAndParseResp(t *testing.T, ctile *tileCachingHandler, url string) (entri
 	if resp.StatusCode != 200 {
 		t.Fatalf("%q: expected status code 200 got %d with body: %q", url, resp.StatusCode, body)
 	}
+	if resp.Header.Get("Content-Encoding") != "gzip" {
+		t.Fatalf("expected Content-Encoding: gzip, got %q", resp.Header.Get("Content-Encoding"))
+	}
+	gzipReader, err := gzip.NewReader(bytes.NewReader(body))
+	if err != nil {
+		t.Fatal(err)
+	}
+	jsonBytes, err := io.ReadAll(gzipReader)
+	if err != nil {
+		t.Fatal(err)
+	}
+
 	var entries entries
-	err := json.Unmarshal(body, &entries)
+	err = json.Unmarshal(jsonBytes, &entries)
 	return entries, resp.Header, err
 }
 

main.go

@@ -18,6 +18,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/NYTimes/gziphandler"
 	"github.com/aws/aws-sdk-go-v2/aws"
 	"github.com/aws/aws-sdk-go-v2/config"
 	"github.com/aws/aws-sdk-go-v2/service/s3"
@@ -294,6 +295,8 @@ type tileCachingHandler struct {
 	backendLatencyMetric *prometheus.HistogramVec
 
 	fullRequestTimeout time.Duration
+
+	gzipHandler http.Handler
 }
 
 func newTileCachingHandler(
@@ -363,7 +366,7 @@ func newTileCachingHandler(
 		[]string{"backend"})
 	promRegisterer.MustRegister(backendLatencyMetric)
 
-	return &tileCachingHandler{
+	tch := tileCachingHandler{
 		logURL:               logURL,
 		tileSize:             tileSize,
 		s3Service:            s3Service,
@@ -376,10 +379,23 @@ func newTileCachingHandler(
 		fullRequestTimeout:   fullRequestTimeout,
 		latencyMetric:        latencyMetric,
 		backendLatencyMetric: backendLatencyMetric,
-	}, nil
+	}
+
+	handlerMaker, err := gziphandler.NewGzipLevelAndMinSize(gzip.BestSpeed, 100)
+	if err != nil {
+		return nil, err
+	}
+
+	tch.gzipHandler = handlerMaker(http.HandlerFunc(tch.serveHTTPInner))
+
+	return &tch, nil
 }
 
 func (tch *tileCachingHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	tch.gzipHandler.ServeHTTP(w, r)
+}
+
+func (tch *tileCachingHandler) serveHTTPInner(w http.ResponseWriter, r *http.Request) {
 	begin := time.Now()
 	defer func() {
 		tch.latencyMetric.Observe(time.Since(begin).Seconds())