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reddit firehose: time-box the read so each pass fits its 60 s slot #281

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Merged
ralyodio merged 1 commit into from
Nov 9, 2026
Merged

reddit firehose: time-box the read so each pass fits its 60 s slot #281

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12 changes: 10 additions & 2 deletions packages/ingest/src/redditFirehose.js
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@ const PAGE = 100;
* lookbackSeconds?: number,
* maxPages?: number,
* gapMs?: number,
* fetchBudgetMs?: number,
* sleep?: (ms: number) => Promise<unknown>,
* maxLagSeconds?: number,
* resumeLagSeconds?: number,
Expand All @@ -41,12 +42,17 @@ export function createRedditFirehose(opts = {}) {
const now = opts.now ?? (() => Date.now());
const fetchPage = opts.fetchPage ?? fetchRedditFirehosePage;
const crawl = opts.crawl ?? crawlFeed;
const maxPages = opts.maxPages ?? 12;
const maxPages = opts.maxPages ?? 30;
// Reading stops at this deadline so the pass (reads plus writes) fits its
// 60 s slot. A pass that overran the slot waited for the *next* one (the
// daemon runs on a fixed grid), which halved throughput to ~6 pages a minute
// against Reddit's ~9 (2026-11-09).
const fetchBudgetMs = opts.fetchBudgetMs ?? 40_000;
const concurrency = opts.concurrency ?? 6;
// Arctic Shift answers 422 "Timeout. Maybe slow down a bit" after ~5 pages
// back to back (measured 2026-11-09), and a page is ~6 s of Reddit, so pages
// are spaced rather than fired: ~11 a minute is just over Reddit's own pace.
const gapMs = opts.gapMs ?? 4_000;
const gapMs = opts.gapMs ?? 3_500;
const sleep = opts.sleep ?? ((ms) => new Promise((resolve) => setTimeout(resolve, ms)));
// Never more than this far behind: past it, skip forward so every feed stays
// inside the hour, and say how much was skipped.
Expand Down Expand Up @@ -75,7 +81,9 @@ export function createRedditFirehose(opts = {}) {
cursor = nowSeconds - resumeLagSeconds;
}

const started = now();
for (; pages < maxPages; pages += 1) {
if (pages > 0 && now() - started + gapMs >= fetchBudgetMs) break;
if (pages > 0 && gapMs > 0) await sleep(gapMs);
let page;
try {
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