cmd/tsconnect: prefetch main.wasm when serving

Avoids waterfalling of requests from the file (its load is triggered from JavaScript). Also has other cleanups to index.html, adding a <title> and moving the <script> to being loaded sooner (but still not delaying page rendering by using the defer attribute). Fixes #5141 Fixes #5135 Signed-off-by: Mihai Parparita <mihai@tailscale.com>
2 years ago · 52d769d35c
parent f04bc31820
commit 52d769d35c
3 changed files with 18 additions and 1 deletions
--- a/cmd/tsconnect/common.go
+++ b/cmd/tsconnect/common.go
@ -119,6 +119,9 @@ func runYarn(args ...string) error {
 // from entry points to hashed file names.
 type EsbuildMetadata struct {
 	Outputs map[string]struct {
+		Inputs map[string]struct {
+			BytesInOutput int64 `json:"bytesInOutput"`
+		} `json:"inputs,omitempty"`
 		EntryPoint string `json:"entryPoint,omitempty"`
 	} `json:"outputs,omitempty"`
 }
--- a/cmd/tsconnect/index.html
+++ b/cmd/tsconnect/index.html
@ -3,7 +3,9 @@
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Tailscale Connect</title>
    <link rel="stylesheet" type="text/css" href="dist/index.css" />
+    <script src="dist/index.js" defer></script>
  </head>
  <body class="flex flex-col h-screen overflow-hidden">
    <div class="bg-gray-100 border-b border-gray-200 pt-4 pb-2">
@ -38,6 +40,5 @@
        enabled. Give it a try!
      </div>
    </div>
-    <script src="dist/index.js"></script>
  </body>
 </html>
--- a/cmd/tsconnect/serve.go
+++ b/cmd/tsconnect/serve.go
@ -83,10 +83,19 @@ func generateServeIndex(distFS fs.FS) ([]byte, error) {
 		return nil, fmt.Errorf("Could not parse esbuild-metadata.json: %w", err)
 	}
 	entryPointsToHashedDistPaths := make(map[string]string)
+	mainWasmPath := ""
 	for outputPath, output := range esbuildMetadata.Outputs {
 		if output.EntryPoint != "" {
 			entryPointsToHashedDistPaths[output.EntryPoint] = path.Join("dist", outputPath)
 		}
+		if path.Ext(outputPath) == ".wasm" {
+			for input := range output.Inputs {
+				if input == "src/main.wasm" {
+					mainWasmPath = path.Join("dist", outputPath)
+					break
+				}
+			}
+		}
 	}

 	indexBytes := rawIndexBytes
@ -96,6 +105,10 @@ func generateServeIndex(distFS fs.FS) ([]byte, error) {
 			indexBytes = bytes.ReplaceAll(indexBytes, []byte(defaultDistPath), []byte(hashedDistPath))
 		}
 	}
+	if mainWasmPath != "" {
+		mainWasmPrefetch := fmt.Sprintf("</title>\n<link rel='preload' as='fetch' crossorigin='anonymous' href='%s'>", mainWasmPath)
+		indexBytes = bytes.ReplaceAll(indexBytes, []byte("</title>"), []byte(mainWasmPrefetch))
+	}

 	return indexBytes, nil
 }