Fixes server ignores request to gzip data (#14982)

* files changed

* Update api/server/middleware/middleware.go

* fixed AcceptEncodingHeaderHandler

* Update changelog/rose2221-develop.md

* Added tests'

* Update api/server/middleware/middleware_test.go

* updated bazel

* formatting

* fixed e2e_test

* zip only json

* zip only json

---------

Co-authored-by: Radosław Kapka <radoslaw.kapka@gmail.com>
Co-authored-by: james-prysm <90280386+james-prysm@users.noreply.github.com>
Co-authored-by: Radosław Kapka <rkapka@wp.pl>

api/server/middleware/BUILD.bazel

@@ -8,7 +8,11 @@ go_library(
     ],
     importpath = "github.com/OffchainLabs/prysm/v6/api/server/middleware",
     visibility = ["//visibility:public"],
-    deps = ["@com_github_rs_cors//:go_default_library"],
+    deps = [
+        "//api:go_default_library",
+        "@com_github_rs_cors//:go_default_library",
+        "@com_github_sirupsen_logrus//:go_default_library",
+    ],
 )
 
 go_test(
@@ -22,5 +26,6 @@ go_test(
         "//api:go_default_library",
         "//testing/assert:go_default_library",
         "//testing/require:go_default_library",
+        "@com_github_sirupsen_logrus//:go_default_library",
     ],
 )

api/server/middleware/middleware.go

@@ -1,11 +1,14 @@
 package middleware
 
 import (
+	"compress/gzip"
 	"fmt"
 	"net/http"
 	"strings"
 
+	"github.com/OffchainLabs/prysm/v6/api"
 	"github.com/rs/cors"
+	log "github.com/sirupsen/logrus"
 )
 
 type Middleware func(http.Handler) http.Handler
@@ -112,6 +115,46 @@ func AcceptHeaderHandler(serverAcceptedTypes []string) Middleware {
 	}
 }
 
+// AcceptEncodingHeaderHandler compresses the response before sending it back to the client, if gzip is supported.
+func AcceptEncodingHeaderHandler() Middleware {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
+				next.ServeHTTP(w, r)
+				return
+			}
+
+			gz := gzip.NewWriter(w)
+			gzipRW := &gzipResponseWriter{gz: gz, ResponseWriter: w}
+			defer func() {
+				if !gzipRW.zipped {
+					return
+				}
+				if err := gz.Close(); err != nil {
+					log.WithError(err).Error("Failed to close gzip writer")
+				}
+			}()
+
+			next.ServeHTTP(gzipRW, r)
+		})
+	}
+}
+
+type gzipResponseWriter struct {
+	gz *gzip.Writer
+	http.ResponseWriter
+	zipped bool
+}
+
+func (g *gzipResponseWriter) Write(b []byte) (int, error) {
+	if strings.Contains(g.Header().Get("Content-Type"), api.JsonMediaType) {
+		g.zipped = true
+		g.Header().Set("Content-Encoding", "gzip")
+		return g.gz.Write(b)
+	}
+	return g.ResponseWriter.Write(b)
+}
+
 func MiddlewareChain(h http.Handler, mw []Middleware) http.Handler {
 	if len(mw) < 1 {
 		return h

api/server/middleware/middleware_test.go

@@ -1,12 +1,16 @@
 package middleware
 
 import (
+	"bytes"
+	"compress/gzip"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
 
 	"github.com/OffchainLabs/prysm/v6/api"
 	"github.com/OffchainLabs/prysm/v6/testing/require"
+	log "github.com/sirupsen/logrus"
 )
 
 func TestNormalizeQueryValuesHandler(t *testing.T) {
@@ -124,6 +128,89 @@ func TestContentTypeHandler(t *testing.T) {
 	}
 }
 
+func TestAcceptEncodingHeaderHandler(t *testing.T) {
+	dummyContent := "Test gzip middleware content"
+	nextHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", r.Header.Get("Accept"))
+		_, err := w.Write([]byte(dummyContent))
+		require.NoError(t, err)
+	})
+
+	handler := AcceptEncodingHeaderHandler()(nextHandler)
+
+	tests := []struct {
+		name             string
+		accept           string
+		acceptEncoding   string
+		expectCompressed bool
+	}{
+		{
+			name:             "Gzip supported",
+			accept:           api.JsonMediaType,
+			acceptEncoding:   "gzip",
+			expectCompressed: true,
+		},
+		{
+			name:             "Multiple encodings supported",
+			accept:           api.JsonMediaType,
+			acceptEncoding:   "deflate, gzip",
+			expectCompressed: true,
+		},
+		{
+			name:             "Gzip not supported",
+			accept:           api.JsonMediaType,
+			acceptEncoding:   "deflate",
+			expectCompressed: false,
+		},
+		{
+			name:             "No accept encoding header",
+			accept:           api.JsonMediaType,
+			acceptEncoding:   "",
+			expectCompressed: false,
+		},
+		{
+			name:             "SSZ",
+			accept:           api.OctetStreamMediaType,
+			acceptEncoding:   "gzip",
+			expectCompressed: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			req := httptest.NewRequest("GET", "/", nil)
+			req.Header.Set("Accept", tt.accept)
+			if tt.acceptEncoding != "" {
+				req.Header.Set("Accept-Encoding", tt.acceptEncoding)
+			}
+			rr := httptest.NewRecorder()
+
+			handler.ServeHTTP(rr, req)
+
+			if tt.expectCompressed {
+				require.Equal(t, "gzip", rr.Header().Get("Content-Encoding"), "Expected Content-Encoding header to be 'gzip'")
+
+				compressedBody := rr.Body.Bytes()
+				require.NotEqual(t, dummyContent, string(compressedBody), "Response body should be compressed and differ from the original")
+
+				gzReader, err := gzip.NewReader(bytes.NewReader(compressedBody))
+				require.NoError(t, err, "Failed to create gzipReader")
+				defer func() {
+					if err := gzReader.Close(); err != nil {
+						log.WithError(err).Error("Failed to close gzip reader")
+					}
+				}()
+
+				decompressedBody, err := io.ReadAll(gzReader)
+				require.NoError(t, err, "Failed to decompress response body")
+				require.Equal(t, dummyContent, string(decompressedBody), "Decompressed content should match the original")
+			} else {
+				require.Equal(t, dummyContent, rr.Body.String(), "Response body should be uncompressed and match the original")
+			}
+		})
+	}
+}
+
 func TestAcceptHeaderHandler(t *testing.T) {
 	acceptedTypes := []string{"application/json", "application/octet-stream"}