Speed up screenshots with chrome-headless-shell #2559
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,139 @@ | ||
| package runner | ||
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||
| import ( | ||
| "fmt" | ||
| "net/http" | ||
| "net/http/httptest" | ||
| "strings" | ||
| "sync" | ||
| "testing" | ||
| "time" | ||
| ) | ||
|
|
||
| const spaHydratedMarker = "hydrated-ok" | ||
|
|
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| // spaHTML is a tiny SPA-style page: it paints a boot screen first, then | ||
| // fetches /app.js which hydrates #root after a short delay. Early captures | ||
| // only contain "boot"; a correct wait must include spaHydratedMarker. | ||
| const spaHTML = `<!doctype html> | ||
| <html><head><title>spa-bench</title></head> | ||
| <body> | ||
| <div id="root">boot</div> | ||
| <script>fetch("/app.js").then(function(r){return r.text()}).then(eval);</script> | ||
| </body></html>` | ||
|
|
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| const spaJS = ` | ||
| setTimeout(function(){ | ||
| document.getElementById("root").textContent = "` + spaHydratedMarker + `"; | ||
| }, 80); | ||
| ` | ||
|
|
||
| func startSPAScreenshotServer(t testing.TB) *httptest.Server { | ||
| t.Helper() | ||
| mux := http.NewServeMux() | ||
| mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { | ||
| w.Header().Set("Content-Type", "text/html; charset=utf-8") | ||
| _, _ = w.Write([]byte(spaHTML)) | ||
| }) | ||
| mux.HandleFunc("/app.js", func(w http.ResponseWriter, r *http.Request) { | ||
| time.Sleep(50 * time.Millisecond) | ||
| w.Header().Set("Content-Type", "application/javascript") | ||
| _, _ = w.Write([]byte(spaJS)) | ||
| }) | ||
| srv := httptest.NewServer(mux) | ||
| t.Cleanup(srv.Close) | ||
| return srv | ||
| } | ||
|
|
||
| func newScreenshotBrowser(t testing.TB, useLocal bool) *Browser { | ||
| t.Helper() | ||
| browser, err := NewBrowser("", useLocal, nil) | ||
| if err != nil { | ||
| t.Skipf("headless browser unavailable: %v", err) | ||
| } | ||
| t.Cleanup(browser.Close) | ||
| return browser | ||
| } | ||
|
|
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| func captureSPA(t testing.TB, browser *Browser, url string) (screenshot []byte, body string) { | ||
| t.Helper() | ||
| screenshot, body, _, err := browser.ScreenshotWithBody(url, 15*time.Second, 200*time.Millisecond, nil, false, nil) | ||
| if err != nil { | ||
| t.Fatalf("screenshot: %v", err) | ||
| } | ||
| return screenshot, body | ||
| } | ||
|
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| func TestScreenshotSPAWaitsForHydration(t *testing.T) { | ||
| srv := startSPAScreenshotServer(t) | ||
| browser := newScreenshotBrowser(t, false) | ||
|
|
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| screenshot, body := captureSPA(t, browser, srv.URL) | ||
| if len(screenshot) == 0 { | ||
| t.Fatal("empty screenshot") | ||
| } | ||
| if !strings.Contains(body, spaHydratedMarker) { | ||
| t.Fatalf("early capture: body missing %q\n%s", spaHydratedMarker, body) | ||
| } | ||
| } | ||
|
|
||
| func TestScreenshotSPAConcurrentNoEarlyCapture(t *testing.T) { | ||
| const workers = 8 | ||
| srv := startSPAScreenshotServer(t) | ||
| browser := newScreenshotBrowser(t, false) | ||
|
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| var wg sync.WaitGroup | ||
| errs := make(chan error, workers) | ||
| for i := 0; i < workers; i++ { | ||
| wg.Add(1) | ||
| go func() { | ||
| defer wg.Done() | ||
| screenshot, body, _, err := browser.ScreenshotWithBody(srv.URL, 15*time.Second, 200*time.Millisecond, nil, false, nil) | ||
| if err != nil { | ||
| errs <- err | ||
| return | ||
| } | ||
| if len(screenshot) == 0 { | ||
| errs <- fmt.Errorf("empty screenshot") | ||
| return | ||
| } | ||
| if !strings.Contains(body, spaHydratedMarker) { | ||
| errs <- fmt.Errorf("early capture: body missing %q", spaHydratedMarker) | ||
| } | ||
| }() | ||
| } | ||
| wg.Wait() | ||
| close(errs) | ||
| for err := range errs { | ||
| t.Error(err) | ||
| } | ||
| } | ||
|
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| // BenchmarkScreenshotSPA times concurrent captures of the local SPA. | ||
| // | ||
| // On linux/amd64, /default uses chrome-headless-shell when available and | ||
| // /local forces a system Chrome via NewBrowser(..., useLocal=true). Compare: | ||
| // | ||
| // go test -bench=BenchmarkScreenshotSPA -benchtime=20s -count=5 ./runner | ||
| func BenchmarkScreenshotSPA(b *testing.B) { | ||
| for _, useLocal := range []bool{false, true} { | ||
| name := "default" | ||
| if useLocal { | ||
| name = "local" | ||
| } | ||
| b.Run(name, func(b *testing.B) { | ||
| srv := startSPAScreenshotServer(b) | ||
| browser := newScreenshotBrowser(b, useLocal) | ||
| b.ResetTimer() | ||
| for i := 0; i < b.N; i++ { | ||
| screenshot, body, _, err := browser.ScreenshotWithBody(srv.URL, 15*time.Second, 200*time.Millisecond, nil, false, nil) | ||
| if err != nil { | ||
| b.Fatalf("screenshot: %v", err) | ||
| } | ||
| if len(screenshot) == 0 || !strings.Contains(body, spaHydratedMarker) { | ||
| b.Fatal("early or empty capture") | ||
| } | ||
| } | ||
|
Comment on lines
+128
to
+136
There was a problem hiding this comment. 🚀 Performance & Scalability | 🟡 Minor | ⚡ Quick win Keep the concurrent benchmark scenario. This loop runs screenshot captures sequentially. It no longer measures the concurrent SPA workload described by the PR objective and cannot reproduce the reported concurrent speedup. Restore a parallel benchmark, or add a separate concurrent sub-benchmark and label this loop as the sequential baseline. 🤖 Prompt for AI Agents |
||
| }) | ||
| } | ||
| } | ||
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