perf: reduce input tarpitting and speed up large-display rendering
Input tarpitting fixes: - terminal.ts: batch stdin writes with 10ms coalescing window (flushes immediately for large payloads like paste), replacing per-keystroke WebSocket messages with fewer, larger frames - server.go: replace per-message time.After() with a reusable timer to eliminate GC pressure from repeated key input - server.go: coalesce queued stdin writes (up to 4KB) into a single PTY write to reduce syscall overhead Screenshot/rendering pipeline optimizations: - tracker.go: stop forcing empty cells to space; let exporters decide what to render, drastically reducing work for mostly-blank terminals - tracker.go: use clear() for dirty map instead of delete-in-loop - svg_exporter.go: skip visually empty cells (blank glyph, default BG, no reverse/underline); still render background rects for colored or reverse-video cells - png_exporter.go: add color parsing cache to avoid redundant hex parsing per cell; add empty cell fast-path; short-circuit blend math for coverage 0 and 255 Dashboard thumbnail concurrency: - server.go: replace single-flight screenshot fetching with limited parallelism (2-4 concurrent requests based on hardwareConcurrency) so large dashboards with many tiles update faster Also fixes typo in dashboard JS (tetagBySlug -> etagBySlug) that silently broke ETag caching for screenshot refreshes. Bumps version to 1.3.32.
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+97
-49
@@ -2,6 +2,7 @@ package webterm
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import (
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"bufio"
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"bytes"
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"compress/gzip"
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"context"
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"crypto/sha1"
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@@ -555,14 +556,36 @@ func (s *LocalServer) handleWebSocket(w http.ResponseWriter, r *http.Request) {
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}
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stdinQueue := make(chan stdinWrite, wsSendQueueMax)
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defer close(stdinQueue)
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// Coalesce small stdin writes (e.g. key repeats) to reduce syscall and locking overhead.
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const stdinCoalesceMaxBytes = 4 * 1024
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go func() {
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var buf bytes.Buffer
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for write := range stdinQueue {
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if !write.session.SendBytes([]byte(write.data)) {
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buf.Reset()
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buf.WriteString(write.data)
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for buf.Len() < stdinCoalesceMaxBytes {
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select {
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case next := <-stdinQueue:
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buf.WriteString(next.data)
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default:
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goto flush
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}
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}
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flush:
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if !write.session.SendBytes(buf.Bytes()) {
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log.Printf("stdin write failed route=%s remote=%s", routeKey, r.RemoteAddr)
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}
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}
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}()
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// Allocate the timeout timer once; avoid time.After() per stdin message.
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stdinTimer := time.NewTimer(stdinWriteTimeout)
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if !stdinTimer.Stop() {
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<-stdinTimer.C
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}
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defer stdinTimer.Stop()
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for {
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messageType, payload, err := conn.ReadMessage()
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if err != nil {
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@@ -589,12 +612,32 @@ func (s *LocalServer) handleWebSocket(w http.ResponseWriter, r *http.Request) {
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if len(envelope) > 1 {
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data, _ = envelope[1].(string)
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}
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write := stdinWrite{session: session, data: data}
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select {
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case stdinQueue <- stdinWrite{session: session, data: data}:
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case <-time.After(stdinWriteTimeout):
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log.Printf("stdin queue saturated route=%s remote=%s: disconnecting client", routeKey, r.RemoteAddr)
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sendJSON([]any{"error", "Input backlog detected"})
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return
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case stdinQueue <- write:
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// queued
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default:
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// Queue is full; wait briefly for it to drain.
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if !stdinTimer.Stop() {
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select {
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case <-stdinTimer.C:
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default:
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}
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}
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stdinTimer.Reset(stdinWriteTimeout)
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select {
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case stdinQueue <- write:
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if !stdinTimer.Stop() {
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select {
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case <-stdinTimer.C:
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default:
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}
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}
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case <-stdinTimer.C:
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log.Printf("stdin queue saturated route=%s remote=%s: disconnecting client", routeKey, r.RemoteAddr)
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sendJSON([]any{"error", "Input backlog detected"})
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return
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}
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}
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}
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case "resize":
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@@ -1168,7 +1211,9 @@ func (s *LocalServer) handleRoot(w http.ResponseWriter, r *http.Request) {
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const etagBySlug = {};
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const refreshQueue = [];
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const queuedRefresh = {};
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let screenshotRequestInFlight = false;
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// Allow limited parallelism when fetching thumbnails so large dashboards update faster.
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const MAX_SCREENSHOT_CONCURRENCY = Math.max(2, Math.min(4, Math.floor((navigator.hardwareConcurrency || 4) / 2)));
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let screenshotRequestsInFlight = 0;
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const grid = document.getElementById('grid');
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const subtitle = document.getElementById('subtitle');
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@@ -1452,48 +1497,51 @@ func (s *LocalServer) handleRoot(w http.ResponseWriter, r *http.Request) {
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window.addEventListener('blur', onDashboardFocusChanged);
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function processRefreshQueue() {
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if (screenshotRequestInFlight || refreshQueue.length === 0 || !dashboardCanRequestScreenshots()) return;
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const slug = refreshQueue.shift();
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delete queuedRefresh[slug];
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const card = cardsBySlug[slug];
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if (!card || !card.img) {
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setTimeout(processRefreshQueue, 0);
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return;
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if (refreshQueue.length === 0 || !dashboardCanRequestScreenshots()) return;
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while (screenshotRequestsInFlight < MAX_SCREENSHOT_CONCURRENCY && refreshQueue.length > 0) {
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const slug = refreshQueue.shift();
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delete queuedRefresh[slug];
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const card = cardsBySlug[slug];
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if (!card || !card.img) {
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continue;
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}
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screenshotRequestsInFlight++;
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const url = screenshotEndpoint + '?route_key=' + encodeURIComponent(slug);
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const controller = new AbortController();
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const timeout = setTimeout(() => controller.abort(), 5000);
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const headers = {};
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if (etagBySlug[slug]) {
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headers['If-None-Match'] = etagBySlug[slug];
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}
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fetch(url, { cache: 'no-cache', headers, signal: controller.signal })
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.then((resp) => {
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const nextETag = resp.headers.get('ETag');
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if (nextETag) {
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etagBySlug[slug] = nextETag;
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}
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if (resp.status === 304) return null;
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if (!resp.ok) throw new Error('screenshot fetch failed');
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return resp.blob();
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})
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.then((blob) => {
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if (!blob) return;
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const currentCard = cardsBySlug[slug];
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if (!currentCard || !currentCard.img) return;
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const previous = activeObjectURLBySlug[slug];
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if (previous) URL.revokeObjectURL(previous);
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const objectURL = URL.createObjectURL(blob);
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activeObjectURLBySlug[slug] = objectURL;
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currentCard.img.src = objectURL;
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})
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.catch(() => {})
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.finally(() => {
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clearTimeout(timeout);
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screenshotRequestsInFlight--;
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setTimeout(processRefreshQueue, 0);
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});
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}
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screenshotRequestInFlight = true;
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const url = screenshotEndpoint + '?route_key=' + encodeURIComponent(slug);
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const controller = new AbortController();
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const timeout = setTimeout(() => controller.abort(), 5000);
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const headers = {};
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if (etagBySlug[slug]) {
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headers['If-None-Match'] = etagBySlug[slug];
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}
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fetch(url, { cache: 'no-cache', headers, signal: controller.signal })
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.then((resp) => {
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const nextETag = resp.headers.get('ETag');
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if (nextETag) {
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etagBySlug[slug] = nextETag;
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}
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if (resp.status === 304) return null;
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if (!resp.ok) throw new Error('screenshot fetch failed');
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return resp.blob();
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})
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.then((blob) => {
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if (!blob) return;
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const currentCard = cardsBySlug[slug];
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if (!currentCard || !currentCard.img) return;
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const previous = activeObjectURLBySlug[slug];
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if (previous) URL.revokeObjectURL(previous);
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const objectURL = URL.createObjectURL(blob);
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activeObjectURLBySlug[slug] = objectURL;
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currentCard.img.src = objectURL;
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})
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.catch(() => {})
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.finally(() => {
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clearTimeout(timeout);
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screenshotRequestInFlight = false;
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setTimeout(processRefreshQueue, 0);
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});
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}
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function queueTileRefresh(slug) {
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@@ -1570,7 +1618,7 @@ func (s *LocalServer) handleRoot(w http.ResponseWriter, r *http.Request) {
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grid.innerHTML = '';
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cardsBySlug = {};
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refreshQueue.length = 0;
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screenshotRequestInFlight = false;
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screenshotRequestsInFlight = 0;
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for (const key in queuedRefresh) {
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delete queuedRefresh[key];
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}
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