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sse: seq plumbing + subscribe-first dedupe dance

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müde 2026-05-17 12:26:00 +02:00
parent 8c186d4fb7
commit 1340a654e7
5 changed files with 197 additions and 37 deletions
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103
hive-fr0nt/assets/terminal.js
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@ -166,36 +166,35 @@
}
}
async function backfill() {
if (!opts.historyUrl) {
if (opts.onBackfillDone) opts.onBackfillDone(0);
return;
}
try {
const resp = await fetch(opts.historyUrl);
if (!resp.ok) {
if (opts.onBackfillDone) opts.onBackfillDone(0);
return;
}
const events = await resp.json();
currentNoAnim = true;
for (const ev of events) dispatch(ev, true);
currentNoAnim = false;
if (events.length) row('note', '─── live (older above) ───');
else placeholder('(connected — waiting for events)');
if (opts.onBackfillDone) opts.onBackfillDone(events.length);
} catch (err) {
console.warn('history backfill failed', err);
if (opts.onBackfillDone) opts.onBackfillDone(0);
}
}
// Subscribe → buffer → fetch history → dedupe → apply.
//
// Race the SSE subscription opens before the history fetch starts.
// Live events that land before history resolves are buffered, not
// rendered. Once the history response (`{ seq, events }`) arrives we:
// 1. Replay `events` (fromHistory=true).
// 2. Drop buffered events with `seq <= history.seq` — they're
// already reflected in the history rows above.
// 3. Apply remaining buffered events (fromHistory=false).
// 4. Switch to live mode: each new SSE event dispatches immediately.
//
// Without this dance an event that fires between history-fetch and
// SSE-subscribe goes missing; without seq dedupe the same event
// shows twice (once via history, once via live buffer). Both bugs
// were latent before.
//
// If `historyUrl` is unset we skip the dance: buffered events apply
// as live the moment the buffer flushes (no dedupe possible without
// a boundary seq).
function start() {
let live = false;
let buffered = [];
function subscribe() {
const es = new EventSource(opts.streamUrl);
es.onmessage = (e) => {
let ev;
try { ev = JSON.parse(e.data); }
catch (err) { row('note', '[parse err] ' + e.data); return; }
if (!live) { buffered.push(ev); return; }
dispatch(ev, false);
if (opts.onLiveEvent) {
try { opts.onLiveEvent(ev); }
@ -206,10 +205,62 @@
if (es.readyState === EventSource.CONNECTING) row('note', '[reconnecting…]');
else row('note', '[disconnected]');
};
return es;
function flushBuffered(boundarySeq) {
const drained = buffered;
buffered = [];
live = true;
for (const ev of drained) {
// ev.seq is set by the server on live frames; absent/0 means
// "no dedupe possible, apply." Historical replays via the
// history endpoint carry no seq either way.
if (boundarySeq != null && typeof ev.seq === 'number' && ev.seq <= boundarySeq) {
continue;
}
dispatch(ev, false);
if (opts.onLiveEvent) {
try { opts.onLiveEvent(ev); }
catch (err) { console.error('onLiveEvent threw', err); }
}
}
}
async function backfill() {
if (!opts.historyUrl) {
flushBuffered(null);
if (opts.onBackfillDone) opts.onBackfillDone(0);
return;
}
try {
const resp = await fetch(opts.historyUrl);
if (!resp.ok) {
flushBuffered(null);
if (opts.onBackfillDone) opts.onBackfillDone(0);
return;
}
const body = await resp.json();
// Accept the envelope `{ seq, events }`. A bare array means
// the server hasn't been updated to include seq yet — treat
// it as "no dedupe possible."
const events = Array.isArray(body) ? body : (body.events || []);
const boundarySeq = Array.isArray(body) ? null : (body.seq ?? null);
currentNoAnim = true;
for (const ev of events) dispatch(ev, true);
currentNoAnim = false;
if (events.length) row('note', '─── live (older above) ───');
else placeholder('(connected — waiting for events)');
flushBuffered(boundarySeq);
if (opts.onBackfillDone) opts.onBackfillDone(events.length);
} catch (err) {
console.warn('history backfill failed', err);
flushBuffered(null);
if (opts.onBackfillDone) opts.onBackfillDone(0);
}
}
return backfill();
}
const ready = backfill().then(subscribe);
const ready = start();
return { row, details, detailsDiff, placeholder, ready };
}