Support Accept-Encoding header weights with Compress middleware

docs/content/middlewares/http/compress.md

@@ -214,3 +214,44 @@ http:
   [http.middlewares.test-compress.compress]
     minResponseBodyBytes = 1200
 ```
+
+### `defaultEncoding`
+
+_Optional, Default=""_
+
+`defaultEncoding` specifies the default encoding if the `Accept-Encoding` header is not in the request or contains a wildcard (`*`).
+
+There is no fallback on the `defaultEncoding` when the header value is empty or unsupported.
+
+```yaml tab="Docker & Swarm"
+labels:
+  - "traefik.http.middlewares.test-compress.compress.defaultEncoding=gzip"
+```
+
+```yaml tab="Kubernetes"
+apiVersion: traefik.io/v1alpha1
+kind: Middleware
+metadata:
+  name: test-compress
+spec:
+  compress:
+    defaultEncoding: gzip
+```
+
+```yaml tab="Consul Catalog"
+- "traefik.http.middlewares.test-compress.compress.defaultEncoding=gzip"
+```
+
+```yaml tab="File (YAML)"
+http:
+  middlewares:
+    test-compress:
+      compress:
+        defaultEncoding: gzip
+```
+
+```toml tab="File (TOML)"
+[http.middlewares]
+  [http.middlewares.test-compress.compress]
+    defaultEncoding = "gzip"
+```

docs/content/reference/dynamic-configuration/docker-labels.yml

@@ -18,6 +18,7 @@
 - "traefik.http.middlewares.middleware05.circuitbreaker.recoveryduration=42s"
 - "traefik.http.middlewares.middleware05.circuitbreaker.responsecode=42"
 - "traefik.http.middlewares.middleware06.compress=true"
+- "traefik.http.middlewares.middleware06.compress.defaultencoding=foobar"
 - "traefik.http.middlewares.middleware06.compress.excludedcontenttypes=foobar, foobar"
 - "traefik.http.middlewares.middleware06.compress.includedcontenttypes=foobar, foobar"
 - "traefik.http.middlewares.middleware06.compress.minresponsebodybytes=42"

docs/content/reference/dynamic-configuration/file.toml

@@ -143,6 +143,7 @@
         excludedContentTypes = ["foobar", "foobar"]
         includedContentTypes = ["foobar", "foobar"]
         minResponseBodyBytes = 42
+        defaultEncoding = "foobar"
     [http.middlewares.Middleware07]
       [http.middlewares.Middleware07.contentType]
         autoDetect = true

docs/content/reference/dynamic-configuration/file.yaml

@@ -152,6 +152,7 @@ http:
           - foobar
           - foobar
         minResponseBodyBytes: 42
+        defaultEncoding: foobar
     Middleware07:
       contentType:
         autoDetect: true

docs/content/reference/dynamic-configuration/kubernetes-crd-definition-v1.yml

@@ -825,6 +825,11 @@ spec:
                   This middleware compresses responses before sending them to the client, using gzip compression.
                   More info: https://doc.traefik.io/traefik/v3.0/middlewares/http/compress/
                 properties:
+                  defaultEncoding:
+                    description: DefaultEncoding specifies the default encoding if
+                      the `Accept-Encoding` header is not in the request or contains
+                      a wildcard (`*`).
+                    type: string
                   excludedContentTypes:
                     description: |-
                       ExcludedContentTypes defines the list of content types to compare the Content-Type header of the incoming requests and responses before compressing.

docs/content/reference/dynamic-configuration/kv-ref.md

@@ -21,6 +21,7 @@ THIS FILE MUST NOT BE EDITED BY HAND
 | `traefik/http/middlewares/Middleware05/circuitBreaker/fallbackDuration` | `42s` |
 | `traefik/http/middlewares/Middleware05/circuitBreaker/recoveryDuration` | `42s` |
 | `traefik/http/middlewares/Middleware05/circuitBreaker/responseCode` | `42` |
+| `traefik/http/middlewares/Middleware06/compress/defaultEncoding` | `foobar` |
 | `traefik/http/middlewares/Middleware06/compress/excludedContentTypes/0` | `foobar` |
 | `traefik/http/middlewares/Middleware06/compress/excludedContentTypes/1` | `foobar` |
 | `traefik/http/middlewares/Middleware06/compress/includedContentTypes/0` | `foobar` |

docs/content/reference/dynamic-configuration/traefik.io_middlewares.yaml

@@ -183,6 +183,11 @@ spec:
                   This middleware compresses responses before sending them to the client, using gzip compression.
                   More info: https://doc.traefik.io/traefik/v3.0/middlewares/http/compress/
                 properties:
+                  defaultEncoding:
+                    description: DefaultEncoding specifies the default encoding if
+                      the `Accept-Encoding` header is not in the request or contains
+                      a wildcard (`*`).
+                    type: string
                   excludedContentTypes:
                     description: |-
                       ExcludedContentTypes defines the list of content types to compare the Content-Type header of the incoming requests and responses before compressing.

integration/fixtures/k8s/01-traefik-crd.yml

@@ -825,6 +825,11 @@ spec:
                   This middleware compresses responses before sending them to the client, using gzip compression.
                   More info: https://doc.traefik.io/traefik/v3.0/middlewares/http/compress/
                 properties:
+                  defaultEncoding:
+                    description: DefaultEncoding specifies the default encoding if
+                      the `Accept-Encoding` header is not in the request or contains
+                      a wildcard (`*`).
+                    type: string
                   excludedContentTypes:
                     description: |-
                       ExcludedContentTypes defines the list of content types to compare the Content-Type header of the incoming requests and responses before compressing.

pkg/config/dynamic/middlewares.go

@@ -174,6 +174,8 @@ type Compress struct {
 	// MinResponseBodyBytes defines the minimum amount of bytes a response body must have to be compressed.
 	// Default: 1024.
 	MinResponseBodyBytes int `json:"minResponseBodyBytes,omitempty" toml:"minResponseBodyBytes,omitempty" yaml:"minResponseBodyBytes,omitempty" export:"true"`
+	// DefaultEncoding specifies the default encoding if the `Accept-Encoding` header is not in the request or contains a wildcard (`*`).
+	DefaultEncoding string `json:"defaultEncoding,omitempty" toml:"defaultEncoding,omitempty" yaml:"defaultEncoding,omitempty" export:"true"`
 }
 
 // +k8s:deepcopy-gen=true

pkg/middlewares/compress/acceptencoding.go

@@ -0,0 +1,137 @@
+package compress
+
+import (
+	"slices"
+	"strconv"
+	"strings"
+)
+
+const acceptEncodingHeader = "Accept-Encoding"
+
+const (
+	brotliName    = "br"
+	gzipName      = "gzip"
+	identityName  = "identity"
+	wildcardName  = "*"
+	notAcceptable = "not_acceptable"
+)
+
+type Encoding struct {
+	Type   string
+	Weight *float64
+}
+
+func getCompressionType(acceptEncoding []string, defaultType string) string {
+	if defaultType == "" {
+		// Keeps the pre-existing default inside Traefik.
+		defaultType = brotliName
+	}
+
+	encodings, hasWeight := parseAcceptEncoding(acceptEncoding)
+
+	if hasWeight {
+		if len(encodings) == 0 {
+			return identityName
+		}
+
+		encoding := encodings[0]
+
+		if encoding.Type == identityName && encoding.Weight != nil && *encoding.Weight == 0 {
+			return notAcceptable
+		}
+
+		if encoding.Type == wildcardName && encoding.Weight != nil && *encoding.Weight == 0 {
+			return notAcceptable
+		}
+
+		if encoding.Type == wildcardName {
+			return defaultType
+		}
+
+		return encoding.Type
+	}
+
+	for _, dt := range []string{brotliName, gzipName} {
+		if slices.ContainsFunc(encodings, func(e Encoding) bool { return e.Type == dt }) {
+			return dt
+		}
+	}
+
+	if slices.ContainsFunc(encodings, func(e Encoding) bool { return e.Type == wildcardName }) {
+		return defaultType
+	}
+
+	return identityName
+}
+
+func parseAcceptEncoding(acceptEncoding []string) ([]Encoding, bool) {
+	var encodings []Encoding
+	var hasWeight bool
+
+	for _, line := range acceptEncoding {
+		for _, item := range strings.Split(strings.ReplaceAll(line, " ", ""), ",") {
+			parsed := strings.SplitN(item, ";", 2)
+			if len(parsed) == 0 {
+				continue
+			}
+
+			switch parsed[0] {
+			case brotliName, gzipName, identityName, wildcardName:
+				// supported encoding
+			default:
+				continue
+			}
+
+			var weight *float64
+			if len(parsed) > 1 && strings.HasPrefix(parsed[1], "q=") {
+				w, _ := strconv.ParseFloat(strings.TrimPrefix(parsed[1], "q="), 64)
+
+				weight = &w
+				hasWeight = true
+			}
+
+			encodings = append(encodings, Encoding{
+				Type:   parsed[0],
+				Weight: weight,
+			})
+		}
+	}
+
+	slices.SortFunc(encodings, compareEncoding)
+
+	return encodings, hasWeight
+}
+
+func compareEncoding(a, b Encoding) int {
+	lhs, rhs := a.Weight, b.Weight
+
+	if lhs == nil && rhs == nil {
+		return 0
+	}
+
+	if lhs == nil && *rhs == 0 {
+		return -1
+	}
+
+	if lhs == nil {
+		return 1
+	}
+
+	if rhs == nil && *lhs == 0 {
+		return 1
+	}
+
+	if rhs == nil {
+		return -1
+	}
+
+	if *lhs < *rhs {
+		return 1
+	}
+
+	if *lhs > *rhs {
+		return -1
+	}
+
+	return 0
+}

pkg/middlewares/compress/acceptencoding_test.go

@@ -0,0 +1,143 @@
+package compress
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_getCompressionType(t *testing.T) {
+	testCases := []struct {
+		desc        string
+		values      []string
+		defaultType string
+		expected    string
+	}{
+		{
+			desc:     "br > gzip (no weight)",
+			values:   []string{"gzip, br"},
+			expected: brotliName,
+		},
+		{
+			desc:     "known compression type (no weight)",
+			values:   []string{"compress, gzip"},
+			expected: gzipName,
+		},
+		{
+			desc:     "unknown compression type (no weight), no encoding",
+			values:   []string{"compress, rar"},
+			expected: identityName,
+		},
+		{
+			desc:     "wildcard return the default compression type",
+			values:   []string{"*"},
+			expected: brotliName,
+		},
+		{
+			desc:        "wildcard return the custom default compression type",
+			values:      []string{"*"},
+			defaultType: "foo",
+			expected:    "foo",
+		},
+		{
+			desc:     "follows weight",
+			values:   []string{"br;q=0.8, gzip;q=1.0, *;q=0.1"},
+			expected: gzipName,
+		},
+		{
+			desc:     "ignore unknown compression type",
+			values:   []string{"compress;q=1.0, gzip;q=0.5"},
+			expected: gzipName,
+		},
+		{
+			desc:     "not acceptable (identity)",
+			values:   []string{"compress;q=1.0, identity;q=0"},
+			expected: notAcceptable,
+		},
+		{
+			desc:     "not acceptable (wildcard)",
+			values:   []string{"compress;q=1.0, *;q=0"},
+			expected: notAcceptable,
+		},
+		{
+			desc:     "non-zero is higher than 0",
+			values:   []string{"gzip, *;q=0"},
+			expected: gzipName,
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			encodingType := getCompressionType(test.values, test.defaultType)
+
+			assert.Equal(t, test.expected, encodingType)
+		})
+	}
+}
+
+func Test_parseAcceptEncoding(t *testing.T) {
+	testCases := []struct {
+		desc         string
+		values       []string
+		expected     []Encoding
+		assertWeight assert.BoolAssertionFunc
+	}{
+		{
+			desc:   "weight",
+			values: []string{"br;q=1.0, gzip;q=0.8, *;q=0.1"},
+			expected: []Encoding{
+				{Type: brotliName, Weight: ptr[float64](1)},
+				{Type: gzipName, Weight: ptr(0.8)},
+				{Type: wildcardName, Weight: ptr(0.1)},
+			},
+			assertWeight: assert.True,
+		},
+		{
+			desc:   "mixed",
+			values: []string{"gzip, br;q=1.0, *;q=0"},
+			expected: []Encoding{
+				{Type: brotliName, Weight: ptr[float64](1)},
+				{Type: gzipName},
+				{Type: wildcardName, Weight: ptr[float64](0)},
+			},
+			assertWeight: assert.True,
+		},
+		{
+			desc:   "no weight",
+			values: []string{"gzip, br, *"},
+			expected: []Encoding{
+				{Type: gzipName},
+				{Type: brotliName},
+				{Type: wildcardName},
+			},
+			assertWeight: assert.False,
+		},
+		{
+			desc:   "weight and identity",
+			values: []string{"gzip;q=1.0, identity; q=0.5, *;q=0"},
+			expected: []Encoding{
+				{Type: gzipName, Weight: ptr[float64](1)},
+				{Type: identityName, Weight: ptr(0.5)},
+				{Type: wildcardName, Weight: ptr[float64](0)},
+			},
+			assertWeight: assert.True,
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			aes, hasWeight := parseAcceptEncoding(test.values)
+
+			assert.Equal(t, test.expected, aes)
+			test.assertWeight(t, hasWeight)
+		})
+	}
+}
+
+func ptr[T any](t T) *T {
+	return &t
+}

pkg/middlewares/compress/compress.go

@@ -7,7 +7,6 @@ import (
 	"mime"
 	"net/http"
 	"slices"
-	"strings"
 
 	"github.com/klauspost/compress/gzhttp"
 	"github.com/traefik/traefik/v3/pkg/config/dynamic"
@@ -24,11 +23,12 @@ const DefaultMinSize = 1024
 
 // Compress is a middleware that allows to compress the response.
 type compress struct {
-	next     http.Handler
-	name     string
-	excludes []string
-	includes []string
-	minSize  int
+	next            http.Handler
+	name            string
+	excludes        []string
+	includes        []string
+	minSize         int
+	defaultEncoding string
 
 	brotliHandler http.Handler
 	gzipHandler   http.Handler
@@ -68,11 +68,12 @@ func New(ctx context.Context, next http.Handler, conf dynamic.Compress, name str
 	}
 
 	c := &compress{
-		next:     next,
-		name:     name,
-		excludes: excludes,
-		includes: includes,
-		minSize:  minSize,
+		next:            next,
+		name:            name,
+		excludes:        excludes,
+		includes:        includes,
+		minSize:         minSize,
+		defaultEncoding: conf.DefaultEncoding,
 	}
 
 	var err error
@@ -109,25 +110,33 @@ func (c *compress) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	// Client doesn't specify a preferred encoding, for compatibility don't encode the request
-	// See https://github.com/traefik/traefik/issues/9734
-	acceptEncoding, ok := req.Header["Accept-Encoding"]
+	acceptEncoding, ok := req.Header[acceptEncodingHeader]
 	if !ok {
+		if c.defaultEncoding != "" {
+			// RFC says: "If no Accept-Encoding header field is in the request, any content coding is considered acceptable by the user agent."
+			// https://www.rfc-editor.org/rfc/rfc9110#field.accept-encoding
+			c.chooseHandler(c.defaultEncoding, rw, req)
+			return
+		}
+
+		// Client doesn't specify a preferred encoding, for compatibility don't encode the request
+		// See https://github.com/traefik/traefik/issues/9734
 		c.next.ServeHTTP(rw, req)
 		return
 	}
 
-	if encodingAccepts(acceptEncoding, "br") {
+	c.chooseHandler(getCompressionType(acceptEncoding, c.defaultEncoding), rw, req)
+}
+
+func (c *compress) chooseHandler(typ string, rw http.ResponseWriter, req *http.Request) {
+	switch typ {
+	case brotliName:
 		c.brotliHandler.ServeHTTP(rw, req)
-		return
-	}
-
-	if encodingAccepts(acceptEncoding, "gzip") {
+	case gzipName:
 		c.gzipHandler.ServeHTTP(rw, req)
-		return
+	default:
+		c.next.ServeHTTP(rw, req)
 	}
-
-	c.next.ServeHTTP(rw, req)
 }
 
 func (c *compress) GetTracingInformation() (string, string, trace.SpanKind) {
@@ -172,19 +181,3 @@ func (c *compress) newBrotliHandler() (http.Handler, error) {
 
 	return wrapper(c.next), nil
 }
-
-func encodingAccepts(acceptEncoding []string, typ string) bool {
-	for _, ae := range acceptEncoding {
-		for _, e := range strings.Split(ae, ",") {
-			parsed := strings.Split(strings.TrimSpace(e), ";")
-			if len(parsed) == 0 {
-				continue
-			}
-			if parsed[0] == typ || parsed[0] == "*" {
-				return true
-			}
-		}
-	}
-
-	return false
-}

pkg/middlewares/compress/compress_test.go

@@ -18,12 +18,9 @@ import (
 )
 
 const (
-	acceptEncodingHeader  = "Accept-Encoding"
 	contentEncodingHeader = "Content-Encoding"
 	contentTypeHeader     = "Content-Type"
 	varyHeader            = "Vary"
-	gzipValue             = "gzip"
-	brotliValue           = "br"
 )
 
 func TestNegotiation(t *testing.T) {
@@ -62,9 +59,9 @@ func TestNegotiation(t *testing.T) {
 			expEncoding:     "br",
 		},
 		{
-			desc:            "multi accept header, prefer br",
+			desc:            "multi accept header, prefer gzip",
 			acceptEncHeader: "gzip;q=1.0, br;q=0.8",
-			expEncoding:     "br",
+			expEncoding:     "gzip",
 		},
 		{
 			desc:            "multi accept header list, prefer br",
@@ -98,7 +95,7 @@ func TestNegotiation(t *testing.T) {
 
 func TestShouldCompressWhenNoContentEncodingHeader(t *testing.T) {
 	req := testhelpers.MustNewRequest(http.MethodGet, "http://localhost", nil)
-	req.Header.Add(acceptEncodingHeader, gzipValue)
+	req.Header.Add(acceptEncodingHeader, gzipName)
 
 	baseBody := generateBytes(gzhttp.DefaultMinSize)
 
@@ -112,7 +109,7 @@ func TestShouldCompressWhenNoContentEncodingHeader(t *testing.T) {
 	rw := httptest.NewRecorder()
 	handler.ServeHTTP(rw, req)
 
-	assert.Equal(t, gzipValue, rw.Header().Get(contentEncodingHeader))
+	assert.Equal(t, gzipName, rw.Header().Get(contentEncodingHeader))
 	assert.Equal(t, acceptEncodingHeader, rw.Header().Get(varyHeader))
 
 	gr, err := gzip.NewReader(rw.Body)
@@ -125,11 +122,11 @@ func TestShouldCompressWhenNoContentEncodingHeader(t *testing.T) {
 
 func TestShouldNotCompressWhenContentEncodingHeader(t *testing.T) {
 	req := testhelpers.MustNewRequest(http.MethodGet, "http://localhost", nil)
-	req.Header.Add(acceptEncodingHeader, gzipValue)
+	req.Header.Add(acceptEncodingHeader, gzipName)
 
 	fakeCompressedBody := generateBytes(gzhttp.DefaultMinSize)
 	next := http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
-		rw.Header().Add(contentEncodingHeader, gzipValue)
+		rw.Header().Add(contentEncodingHeader, gzipName)
 		rw.Header().Add(varyHeader, acceptEncodingHeader)
 		_, err := rw.Write(fakeCompressedBody)
 		if err != nil {
@@ -142,7 +139,7 @@ func TestShouldNotCompressWhenContentEncodingHeader(t *testing.T) {
 	rw := httptest.NewRecorder()
 	handler.ServeHTTP(rw, req)
 
-	assert.Equal(t, gzipValue, rw.Header().Get(contentEncodingHeader))
+	assert.Equal(t, gzipName, rw.Header().Get(contentEncodingHeader))
 	assert.Equal(t, acceptEncodingHeader, rw.Header().Get(varyHeader))
 
 	assert.EqualValues(t, rw.Body.Bytes(), fakeCompressedBody)
@@ -225,7 +222,7 @@ func TestShouldNotCompressWhenEmptyAcceptEncodingHeader(t *testing.T) {
 
 func TestShouldNotCompressHeadRequest(t *testing.T) {
 	req := testhelpers.MustNewRequest(http.MethodHead, "http://localhost", nil)
-	req.Header.Add(acceptEncodingHeader, gzipValue)
+	req.Header.Add(acceptEncodingHeader, gzipName)
 
 	fakeBody := generateBytes(gzhttp.DefaultMinSize)
 	next := http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
@@ -301,7 +298,7 @@ func TestShouldNotCompressWhenSpecificContentType(t *testing.T) {
 			t.Parallel()
 
 			req := testhelpers.MustNewRequest(http.MethodGet, "http://localhost", nil)
-			req.Header.Add(acceptEncodingHeader, gzipValue)
+			req.Header.Add(acceptEncodingHeader, gzipName)
 			if test.reqContentType != "" {
 				req.Header.Add(contentTypeHeader, test.reqContentType)
 			}
@@ -352,7 +349,7 @@ func TestShouldCompressWhenSpecificContentType(t *testing.T) {
 			t.Parallel()
 
 			req := testhelpers.MustNewRequest(http.MethodGet, "http://localhost", nil)
-			req.Header.Add(acceptEncodingHeader, gzipValue)
+			req.Header.Add(acceptEncodingHeader, gzipName)
 
 			next := http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
 				rw.Header().Set(contentTypeHeader, test.respContentType)
@@ -368,7 +365,7 @@ func TestShouldCompressWhenSpecificContentType(t *testing.T) {
 			rw := httptest.NewRecorder()
 			handler.ServeHTTP(rw, req)
 
-			assert.Equal(t, gzipValue, rw.Header().Get(contentEncodingHeader))
+			assert.Equal(t, gzipName, rw.Header().Get(contentEncodingHeader))
 			assert.Equal(t, acceptEncodingHeader, rw.Header().Get(varyHeader))
 			assert.NotEqualValues(t, rw.Body.Bytes(), baseBody)
 		})
@@ -386,7 +383,7 @@ func TestIntegrationShouldNotCompress(t *testing.T) {
 		{
 			name: "when content already compressed",
 			handler: http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
-				rw.Header().Add(contentEncodingHeader, gzipValue)
+				rw.Header().Add(contentEncodingHeader, gzipName)
 				rw.Header().Add(varyHeader, acceptEncodingHeader)
 				_, err := rw.Write(fakeCompressedBody)
 				if err != nil {
@@ -398,7 +395,7 @@ func TestIntegrationShouldNotCompress(t *testing.T) {
 		{
 			name: "when content already compressed and status code Created",
 			handler: http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
-				rw.Header().Add(contentEncodingHeader, gzipValue)
+				rw.Header().Add(contentEncodingHeader, gzipName)
 				rw.Header().Add(varyHeader, acceptEncodingHeader)
 				rw.WriteHeader(http.StatusCreated)
 				_, err := rw.Write(fakeCompressedBody)
@@ -419,14 +416,14 @@ func TestIntegrationShouldNotCompress(t *testing.T) {
 			defer ts.Close()
 
 			req := testhelpers.MustNewRequest(http.MethodGet, ts.URL, nil)
-			req.Header.Add(acceptEncodingHeader, gzipValue)
+			req.Header.Add(acceptEncodingHeader, gzipName)
 
 			resp, err := http.DefaultClient.Do(req)
 			require.NoError(t, err)
 
 			assert.Equal(t, test.expectedStatusCode, resp.StatusCode)
 
-			assert.Equal(t, gzipValue, resp.Header.Get(contentEncodingHeader))
+			assert.Equal(t, gzipName, resp.Header.Get(contentEncodingHeader))
 			assert.Equal(t, acceptEncodingHeader, resp.Header.Get(varyHeader))
 
 			body, err := io.ReadAll(resp.Body)
@@ -438,7 +435,7 @@ func TestIntegrationShouldNotCompress(t *testing.T) {
 
 func TestShouldWriteHeaderWhenFlush(t *testing.T) {
 	next := http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
-		rw.Header().Add(contentEncodingHeader, gzipValue)
+		rw.Header().Add(contentEncodingHeader, gzipName)
 		rw.Header().Add(varyHeader, acceptEncodingHeader)
 		rw.WriteHeader(http.StatusUnauthorized)
 		rw.(http.Flusher).Flush()
@@ -454,14 +451,14 @@ func TestShouldWriteHeaderWhenFlush(t *testing.T) {
 	defer ts.Close()
 
 	req := testhelpers.MustNewRequest(http.MethodGet, ts.URL, nil)
-	req.Header.Add(acceptEncodingHeader, gzipValue)
+	req.Header.Add(acceptEncodingHeader, gzipName)
 
 	resp, err := http.DefaultClient.Do(req)
 	require.NoError(t, err)
 
 	assert.Equal(t, http.StatusUnauthorized, resp.StatusCode)
 
-	assert.Equal(t, gzipValue, resp.Header.Get(contentEncodingHeader))
+	assert.Equal(t, gzipName, resp.Header.Get(contentEncodingHeader))
 	assert.Equal(t, acceptEncodingHeader, resp.Header.Get(varyHeader))
 }
 
@@ -505,14 +502,14 @@ func TestIntegrationShouldCompress(t *testing.T) {
 			defer ts.Close()
 
 			req := testhelpers.MustNewRequest(http.MethodGet, ts.URL, nil)
-			req.Header.Add(acceptEncodingHeader, gzipValue)
+			req.Header.Add(acceptEncodingHeader, gzipName)
 
 			resp, err := http.DefaultClient.Do(req)
 			require.NoError(t, err)
 
 			assert.Equal(t, test.expectedStatusCode, resp.StatusCode)
 
-			assert.Equal(t, gzipValue, resp.Header.Get(contentEncodingHeader))
+			assert.Equal(t, gzipName, resp.Header.Get(contentEncodingHeader))
 			assert.Equal(t, acceptEncodingHeader, resp.Header.Get(varyHeader))
 
 			body, err := io.ReadAll(resp.Body)
@@ -547,7 +544,7 @@ func TestMinResponseBodyBytes(t *testing.T) {
 			t.Parallel()
 
 			req := testhelpers.MustNewRequest(http.MethodGet, "http://localhost", nil)
-			req.Header.Add(acceptEncodingHeader, gzipValue)
+			req.Header.Add(acceptEncodingHeader, gzipName)
 
 			next := http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
 				if _, err := rw.Write(fakeBody); err != nil {
@@ -562,7 +559,7 @@ func TestMinResponseBodyBytes(t *testing.T) {
 			handler.ServeHTTP(rw, req)
 
 			if test.expectedCompression {
-				assert.Equal(t, gzipValue, rw.Header().Get(contentEncodingHeader))
+				assert.Equal(t, gzipName, rw.Header().Get(contentEncodingHeader))
 				assert.NotEqualValues(t, rw.Body.Bytes(), fakeBody)
 				return
 			}
@@ -636,7 +633,7 @@ func Test1xxResponses(t *testing.T) {
 		},
 	}
 	req, _ := http.NewRequestWithContext(httptrace.WithClientTrace(context.Background(), trace), http.MethodGet, server.URL, nil)
-	req.Header.Add(acceptEncodingHeader, gzipValue)
+	req.Header.Add(acceptEncodingHeader, gzipName)
 
 	res, err := frontendClient.Do(req)
 	assert.NoError(t, err)
@@ -648,7 +645,7 @@ func Test1xxResponses(t *testing.T) {
 	}
 	checkLinkHeaders(t, []string{"</style.css>; rel=preload; as=style", "</script.js>; rel=preload; as=script", "</foo.js>; rel=preload; as=script"}, res.Header["Link"])
 
-	assert.Equal(t, gzipValue, res.Header.Get(contentEncodingHeader))
+	assert.Equal(t, gzipName, res.Header.Get(contentEncodingHeader))
 	body, _ := io.ReadAll(res.Body)
 	assert.NotEqualValues(t, body, fakeBody)
 }
@@ -730,7 +727,7 @@ func runBenchmark(b *testing.B, req *http.Request, handler http.Handler) {
 		b.Fatalf("Expected 200 but got %d", code)
 	}
 
-	assert.Equal(b, gzipValue, res.Header().Get(contentEncodingHeader))
+	assert.Equal(b, gzipName, res.Header().Get(contentEncodingHeader))
 }
 
 func generateBytes(length int) []byte {