chore: expose original length when serving slim binaries (#17735)

deansheather · web-flow · commit c7917ea9e501 · 2025-05-16T15:19:28.000+10:00
This will be used in the extensions and desktop apps to enable compression AND progress reporting for the download by comparing the original content length to the amount of bytes written to disk. Closes #16340
diff --git a/site/site.go b/site/site.go
@@ -108,10 +108,34 @@ func New(opts *Options) *Handler {
 		panic(fmt.Sprintf("Failed to parse html files: %v", err))
 	}
 
-	binHashCache := newBinHashCache(opts.BinFS, opts.BinHashes)
-
 	mux := http.NewServeMux()
-	mux.Handle("/bin/", http.StripPrefix("/bin", http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+	mux.Handle("/bin/", binHandler(opts.BinFS, newBinMetadataCache(opts.BinFS, opts.BinHashes)))
+	mux.Handle("/", http.FileServer(
+		http.FS(
+			// OnlyFiles is a wrapper around the file system that prevents directory
+			// listings. Directory listings are not required for the site file system, so we
+			// exclude it as a security measure. In practice, this file system comes from our
+			// open source code base, but this is considered a best practice for serving
+			// static files.
+			OnlyFiles(opts.SiteFS))),
+	)
+	buildInfoResponse, err := json.Marshal(opts.BuildInfo)
+	if err != nil {
+		panic("failed to marshal build info: " + err.Error())
+	}
+	handler.buildInfoJSON = html.EscapeString(string(buildInfoResponse))
+	handler.handler = mux.ServeHTTP
+
+	handler.installScript, err = parseInstallScript(opts.SiteFS, opts.BuildInfo)
+	if err != nil {
+		opts.Logger.Warn(context.Background(), "could not parse install.sh, it will be unavailable", slog.Error(err))
+	}
+
+	return handler
+}
+
+func binHandler(binFS http.FileSystem, binMetadataCache *binMetadataCache) http.Handler {
+	return http.StripPrefix("/bin", http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
 		// Convert underscores in the filename to hyphens. We eventually want to
 		// change our hyphen-based filenames to underscores, but we need to
 		// support both for now.
@@ -122,7 +146,7 @@ func New(opts *Options) *Handler {
 		if name == "" || name == "/" {
 			// Serve the directory listing. This intentionally allows directory listings to
 			// be served. This file system should not contain anything sensitive.
-			http.FileServer(opts.BinFS).ServeHTTP(rw, r)
+			http.FileServer(binFS).ServeHTTP(rw, r)
 			return
 		}
 		if strings.Contains(name, "/") {
@@ -131,7 +155,8 @@ func New(opts *Options) *Handler {
 			http.NotFound(rw, r)
 			return
 		}
-		hash, err := binHashCache.getHash(name)
+
+		metadata, err := binMetadataCache.getMetadata(name)
 		if xerrors.Is(err, os.ErrNotExist) {
 			http.NotFound(rw, r)
 			return
@@ -141,35 +166,26 @@ func New(opts *Options) *Handler {
 			return
 		}
 
-		// ETag header needs to be quoted.
-		rw.Header().Set("ETag", fmt.Sprintf(`%q`, hash))
+		// http.FileServer will not set Content-Length when performing chunked
+		// transport encoding, which is used for large files like our binaries
+		// so stream compression can be used.
+		//
+		// Clients like IDE extensions and the desktop apps can compare the
+		// value of this header with the amount of bytes written to disk after
+		// decompression to show progress. Without this, they cannot show
+		// progress without disabling compression.
+		//
+		// There isn't really a spec for a length header for the "inner" content
+		// size, but some nginx modules use this header.
+		rw.Header().Set("X-Original-Content-Length", fmt.Sprintf("%d", metadata.sizeBytes))
+
+		// Get and set ETag header. Must be quoted.
+		rw.Header().Set("ETag", fmt.Sprintf(`%q`, metadata.sha1Hash))
 
 		// http.FileServer will see the ETag header and automatically handle
 		// If-Match and If-None-Match headers on the request properly.
-		http.FileServer(opts.BinFS).ServeHTTP(rw, r)
-	})))
-	mux.Handle("/", http.FileServer(
-		http.FS(
-			// OnlyFiles is a wrapper around the file system that prevents directory
-			// listings. Directory listings are not required for the site file system, so we
-			// exclude it as a security measure. In practice, this file system comes from our
-			// open source code base, but this is considered a best practice for serving
-			// static files.
-			OnlyFiles(opts.SiteFS))),
-	)
-	buildInfoResponse, err := json.Marshal(opts.BuildInfo)
-	if err != nil {
-		panic("failed to marshal build info: " + err.Error())
-	}
-	handler.buildInfoJSON = html.EscapeString(string(buildInfoResponse))
-	handler.handler = mux.ServeHTTP
-
-	handler.installScript, err = parseInstallScript(opts.SiteFS, opts.BuildInfo)
-	if err != nil {
-		opts.Logger.Warn(context.Background(), "could not parse install.sh, it will be unavailable", slog.Error(err))
-	}
-
-	return handler
+		http.FileServer(binFS).ServeHTTP(rw, r)
+	}))
 }
 
 type Handler struct {
@@ -217,7 +233,7 @@ func (h *Handler) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 		h.handler.ServeHTTP(rw, r)
 		return
 	// If requesting assets, serve straight up with caching.
-	case reqFile == "assets" || strings.HasPrefix(reqFile, "assets/"):
+	case reqFile == "assets" || strings.HasPrefix(reqFile, "assets/") || strings.HasPrefix(reqFile, "icon/"):
 		// It could make sense to cache 404s, but the problem is that during an
 		// upgrade a load balancer may route partially to the old server, and that
 		// would make new asset paths get cached as 404s and not load even once the
@@ -952,68 +968,95 @@ func RenderStaticErrorPage(rw http.ResponseWriter, r *http.Request, data ErrorPa
 	}
 }
 
-type binHashCache struct {
-	binFS http.FileSystem
+type binMetadata struct {
+	sizeBytes int64 // -1 if not known yet
+	// SHA1 was chosen because it's fast to compute and reasonable for
+	// determining if a file has changed. The ETag is not used a security
+	// measure.
+	sha1Hash string // always set if in the cache
+}
+
+type binMetadataCache struct {
+	binFS          http.FileSystem
+	originalHashes map[string]string
 
-	hashes map[string]string
-	mut    sync.RWMutex
-	sf     singleflight.Group
-	sem    chan struct{}
+	metadata map[string]binMetadata
+	mut      sync.RWMutex
+	sf       singleflight.Group
+	sem      chan struct{}
 }
 
-func newBinHashCache(binFS http.FileSystem, binHashes map[string]string) *binHashCache {
-	b := &binHashCache{
-		binFS:  binFS,
-		hashes: make(map[string]string, len(binHashes)),
-		mut:    sync.RWMutex{},
-		sf:     singleflight.Group{},
-		sem:    make(chan struct{}, 4),
+func newBinMetadataCache(binFS http.FileSystem, binSha1Hashes map[string]string) *binMetadataCache {
+	b := &binMetadataCache{
+		binFS:          binFS,
+		originalHashes: make(map[string]string, len(binSha1Hashes)),
+
+		metadata: make(map[string]binMetadata, len(binSha1Hashes)),
+		mut:      sync.RWMutex{},
+		sf:       singleflight.Group{},
+		sem:      make(chan struct{}, 4),
 	}
-	// Make a copy since we're gonna be mutating it.
-	for k, v := range binHashes {
-		b.hashes[k] = v
+
+	// Previously we copied binSha1Hashes to the cache immediately. Since we now
+	// read other information like size from the file, we can't do that. Instead
+	// we copy the hashes to a different map that will be used to populate the
+	// cache on the first request.
+	for k, v := range binSha1Hashes {
+		b.originalHashes[k] = v
 	}
 
 	return b
 }
 
-func (b *binHashCache) getHash(name string) (string, error) {
+func (b *binMetadataCache) getMetadata(name string) (binMetadata, error) {
 	b.mut.RLock()
-	hash, ok := b.hashes[name]
+	metadata, ok := b.metadata[name]
 	b.mut.RUnlock()
 	if ok {
-		return hash, nil
+		return metadata, nil
 	}
 
 	// Avoid DOS by using a pool, and only doing work once per file.
-	v, err, _ := b.sf.Do(name, func() (interface{}, error) {
+	v, err, _ := b.sf.Do(name, func() (any, error) {
 		b.sem <- struct{}{}
 		defer func() { <-b.sem }()
 
 		f, err := b.binFS.Open(name)
 		if err != nil {
-			return "", err
+			return binMetadata{}, err
 		}
 		defer f.Close()
 
-		h := sha1.New() //#nosec // Not used for cryptography.
-		_, err = io.Copy(h, f)
+		var metadata binMetadata
+
+		stat, err := f.Stat()
 		if err != nil {
-			return "", err
+			return binMetadata{}, err
+		}
+		metadata.sizeBytes = stat.Size()
+
+		if hash, ok := b.originalHashes[name]; ok {
+			metadata.sha1Hash = hash
+		} else {
+			h := sha1.New() //#nosec // Not used for cryptography.
+			_, err := io.Copy(h, f)
+			if err != nil {
+				return binMetadata{}, err
+			}
+			metadata.sha1Hash = hex.EncodeToString(h.Sum(nil))
 		}
 
-		hash := hex.EncodeToString(h.Sum(nil))
 		b.mut.Lock()
-		b.hashes[name] = hash
+		b.metadata[name] = metadata
 		b.mut.Unlock()
-		return hash, nil
+		return metadata, nil
 	})
 	if err != nil {
-		return "", err
+		return binMetadata{}, err
 	}
 
 	//nolint:forcetypeassert
-	return strings.ToLower(v.(string)), nil
+	return v.(binMetadata), nil
 }
 
 func applicationNameOrDefault(cfg codersdk.AppearanceConfig) string {
diff --git a/site/site_test.go b/site/site_test.go
@@ -19,6 +19,7 @@ import (
 	"time"
 
 	"github.com/go-chi/chi/v5"
+	"github.com/go-chi/chi/v5/middleware"
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -373,11 +374,13 @@ func TestServingBin(t *testing.T) {
 	delete(sampleBinFSMissingSha256, binCoderSha1)
 
 	type req struct {
-		url         string
-		ifNoneMatch string
-		wantStatus  int
-		wantBody    []byte
-		wantEtag    string
+		url              string
+		ifNoneMatch      string
+		wantStatus       int
+		wantBody         []byte
+		wantOriginalSize int
+		wantEtag         string
+		compression      bool
 	}
 	tests := []struct {
 		name    string
@@ -390,17 +393,27 @@ func TestServingBin(t *testing.T) {
 			fs:   sampleBinFS(),
 			reqs: []req{
 				{
-					url:        "/bin/coder-linux-amd64",
-					wantStatus: http.StatusOK,
-					wantBody:   []byte("compressed"),
-					wantEtag:   fmt.Sprintf("%q", sampleBinSHAs["coder-linux-amd64"]),
+					url:              "/bin/coder-linux-amd64",
+					wantStatus:       http.StatusOK,
+					wantBody:         []byte("compressed"),
+					wantOriginalSize: 10,
+					wantEtag:         fmt.Sprintf("%q", sampleBinSHAs["coder-linux-amd64"]),
 				},
 				// Test ETag support.
 				{
-					url:         "/bin/coder-linux-amd64",
-					ifNoneMatch: fmt.Sprintf("%q", sampleBinSHAs["coder-linux-amd64"]),
-					wantStatus:  http.StatusNotModified,
-					wantEtag:    fmt.Sprintf("%q", sampleBinSHAs["coder-linux-amd64"]),
+					url:              "/bin/coder-linux-amd64",
+					ifNoneMatch:      fmt.Sprintf("%q", sampleBinSHAs["coder-linux-amd64"]),
+					wantStatus:       http.StatusNotModified,
+					wantOriginalSize: 10,
+					wantEtag:         fmt.Sprintf("%q", sampleBinSHAs["coder-linux-amd64"]),
+				},
+				// Test compression support with X-Original-Content-Length
+				// header.
+				{
+					url:              "/bin/coder-linux-amd64",
+					wantStatus:       http.StatusOK,
+					wantOriginalSize: 10,
+					compression:      true,
 				},
 				{url: "/bin/GITKEEP", wantStatus: http.StatusNotFound},
 			},
@@ -462,9 +475,24 @@ func TestServingBin(t *testing.T) {
 			},
 			reqs: []req{
 				// We support both hyphens and underscores for compatibility.
-				{url: "/bin/coder-linux-amd64", wantStatus: http.StatusOK, wantBody: []byte("embed")},
-				{url: "/bin/coder_linux_amd64", wantStatus: http.StatusOK, wantBody: []byte("embed")},
-				{url: "/bin/GITKEEP", wantStatus: http.StatusOK, wantBody: []byte("")},
+				{
+					url:              "/bin/coder-linux-amd64",
+					wantStatus:       http.StatusOK,
+					wantBody:         []byte("embed"),
+					wantOriginalSize: 5,
+				},
+				{
+					url:              "/bin/coder_linux_amd64",
+					wantStatus:       http.StatusOK,
+					wantBody:         []byte("embed"),
+					wantOriginalSize: 5,
+				},
+				{
+					url:              "/bin/GITKEEP",
+					wantStatus:       http.StatusOK,
+					wantBody:         []byte(""),
+					wantOriginalSize: 0,
+				},
 			},
 		},
 	}
@@ -482,12 +510,14 @@ func TestServingBin(t *testing.T) {
 				require.Error(t, err, "extraction or read did not fail")
 			}
 
-			srv := httptest.NewServer(site.New(&site.Options{
+			site := site.New(&site.Options{
 				Telemetry: telemetry.NewNoop(),
 				BinFS:     binFS,
 				BinHashes: binHashes,
 				SiteFS:    rootFS,
-			}))
+			})
+			compressor := middleware.NewCompressor(1, "text/*", "application/*")
+			srv := httptest.NewServer(compressor.Handler(site))
 			defer srv.Close()
 
 			// Create a context
@@ -502,6 +532,9 @@ func TestServingBin(t *testing.T) {
 					if tr.ifNoneMatch != "" {
 						req.Header.Set("If-None-Match", tr.ifNoneMatch)
 					}
+					if tr.compression {
+						req.Header.Set("Accept-Encoding", "gzip")
+					}
 
 					resp, err := http.DefaultClient.Do(req)
 					require.NoError(t, err, "http do failed")
@@ -520,10 +553,28 @@ func TestServingBin(t *testing.T) {
 						assert.Empty(t, gotBody, "body is not empty")
 					}
 
+					if tr.compression {
+						assert.Equal(t, "gzip", resp.Header.Get("Content-Encoding"), "content encoding is not gzip")
+					} else {
+						assert.Empty(t, resp.Header.Get("Content-Encoding"), "content encoding is not empty")
+					}
+
 					if tr.wantEtag != "" {
 						assert.NotEmpty(t, resp.Header.Get("ETag"), "etag header is empty")
 						assert.Equal(t, tr.wantEtag, resp.Header.Get("ETag"), "etag did not match")
 					}
+
+					if tr.wantOriginalSize > 0 {
+						// This is a custom header that we set to help the
+						// client know the size of the decompressed data. See
+						// the comment in site.go.
+						headerStr := resp.Header.Get("X-Original-Content-Length")
+						assert.NotEmpty(t, headerStr, "X-Original-Content-Length header is empty")
+						originalSize, err := strconv.Atoi(headerStr)
+						if assert.NoErrorf(t, err, "could not parse X-Original-Content-Length header %q", headerStr) {
+							assert.EqualValues(t, tr.wantOriginalSize, originalSize, "X-Original-Content-Length did not match")
+						}
+					}
 				})
 			}
 		})
