feat: set Content-Length header in all cache backend Open/Stat responses

client/client.go

@@ -30,7 +30,6 @@ func (e *HTTPStatusError) Error() string {
 // transportHeaders are headers added by the HTTP transport layer that should
 // not be surfaced as cached-object metadata on responses.
 var transportHeaders = []string{ //nolint:gochecknoglobals
-	"Content-Length",
 	"Date",
 	"Accept-Encoding",
 	"User-Agent",

internal/cache/cachetest/suite.go

@@ -5,6 +5,7 @@ import (
 	"io"
 	"net/http"
 	"os"
+	"strconv"
 	"testing"
 	"time"
 
@@ -57,6 +58,10 @@ func Suite(t *testing.T, newCache func(t *testing.T) cache.Cache) {
 		testLastModified(t, newCache(t))
 	})
 
+	t.Run("ContentLength", func(t *testing.T) {
+		testContentLength(t, newCache(t))
+	})
+
 	t.Run("NamespaceIsolation", func(t *testing.T) {
 		testNamespaceIsolation(t, newCache(t))
 	})
@@ -343,6 +348,29 @@ func testLastModified(t *testing.T, c cache.Cache) {
 	assert.Equal(t, explicitTime.Format(http.TimeFormat), headers2.Get("Last-Modified"))
 }
 
+func testContentLength(t *testing.T, c cache.Cache) {
+	defer c.Close()
+	ctx := t.Context()
+
+	content := []byte("hello content length")
+	key := cache.NewKey("test-content-length")
+
+	w, err := c.Create(ctx, key, nil, time.Hour)
+	assert.NoError(t, err)
+	_, err = w.Write(content)
+	assert.NoError(t, err)
+	assert.NoError(t, w.Close())
+
+	reader, headers, err := c.Open(ctx, key)
+	assert.NoError(t, err)
+	defer reader.Close()
+	assert.Equal(t, strconv.Itoa(len(content)), headers.Get("Content-Length"))
+
+	statHeaders, err := c.Stat(ctx, key)
+	assert.NoError(t, err)
+	assert.Equal(t, strconv.Itoa(len(content)), statHeaders.Get("Content-Length"))
+}
+
 func testNamespaceIsolation(t *testing.T, c cache.Cache) {
 	defer c.Close()
 	ctx := t.Context()

internal/cache/disk.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"path/filepath"
 	"sort"
+	"strconv"
 	"sync/atomic"
 	"time"
 
@@ -234,7 +235,8 @@ func (d *Disk) Stat(ctx context.Context, key Key) (http.Header, error) {
 	path := d.keyToPath(d.namespace, key)
 	fullPath := filepath.Join(d.config.Root, path)
 
-	if _, err := os.Stat(fullPath); err != nil {
+	info, err := os.Stat(fullPath)
+	if err != nil {
 		return nil, errors.Errorf("failed to stat file: %w", err)
 	}
 
@@ -252,6 +254,7 @@ func (d *Disk) Stat(ctx context.Context, key Key) (http.Header, error) {
 		return nil, errors.Errorf("failed to get headers: %w", err)
 	}
 
+	headers.Set("Content-Length", strconv.FormatInt(info.Size(), 10))
 	return headers, nil
 }
 
@@ -279,6 +282,12 @@ func (d *Disk) Open(ctx context.Context, key Key) (io.ReadCloser, http.Header, e
 		return nil, nil, errors.Join(errors.Errorf("failed to get headers: %w", err), f.Close())
 	}
 
+	finfo, err := f.Stat()
+	if err != nil {
+		return nil, nil, errors.Join(errors.Errorf("failed to stat file for size: %w", err), f.Close())
+	}
+	headers.Set("Content-Length", strconv.FormatInt(finfo.Size(), 10))
+
 	// Reset expiration time to implement LRU
 	ttl := min(expiresAt.Sub(now), d.config.MaxTTL)
 	newExpiresAt := now.Add(ttl)

internal/cache/memory.go

@@ -8,6 +8,7 @@ import (
 	"maps"
 	"net/http"
 	"os"
+	"strconv"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -75,7 +76,9 @@ func (m *Memory) Stat(_ context.Context, key Key) (http.Header, error) {
 		return nil, os.ErrNotExist
 	}
 
-	return entry.headers, nil
+	headers := maps.Clone(entry.headers)
+	headers.Set("Content-Length", strconv.Itoa(len(entry.data)))
+	return headers, nil
 }
 
 func (m *Memory) Open(_ context.Context, key Key) (io.ReadCloser, http.Header, error) {
@@ -96,7 +99,9 @@ func (m *Memory) Open(_ context.Context, key Key) (io.ReadCloser, http.Header, e
 		return nil, nil, os.ErrNotExist
 	}
 
-	return io.NopCloser(bytes.NewReader(entry.data)), entry.headers, nil
+	headers := maps.Clone(entry.headers)
+	headers.Set("Content-Length", strconv.Itoa(len(entry.data)))
+	return io.NopCloser(bytes.NewReader(entry.data)), headers, nil
 }
 
 func (m *Memory) Create(ctx context.Context, key Key, headers http.Header, ttl time.Duration) (Writer, error) {

internal/cache/s3.go

@@ -162,8 +162,12 @@ func (s *S3) statAndHeaders(ctx context.Context, key Key) (minio.ObjectInfo, htt
 }
 
 func (s *S3) Stat(ctx context.Context, key Key) (http.Header, error) {
-	_, headers, err := s.statAndHeaders(ctx, key)
-	return headers, err
+	objInfo, headers, err := s.statAndHeaders(ctx, key)
+	if err != nil {
+		return nil, err
+	}
+	headers.Set("Content-Length", strconv.FormatInt(objInfo.Size, 10))
+	return headers, nil
 }
 
 func (s *S3) Open(ctx context.Context, key Key) (io.ReadCloser, http.Header, error) {