Zakhar Timoshenko
c0487e4c2a
- Added PSU_CONTACT environment variable to docker-compose for owner contact in User-Agent. - Updated source.js to include user-agent construction with service version and contact information. - Implemented exponential backoff strategy for failed requests to the university, with retry logic based on HTTP response status. - Modified status.js to display backoff information in the status response. - Adjusted watch.js to reduce request frequency during university downtime. - Enhanced test coverage with new backoff.test.js to validate backoff behavior and user-agent format.
45 lines
1.7 KiB
JavaScript
45 lines
1.7 KiB
JavaScript
import { getCatalog, catalogFailure } from "./source.js";
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import { syncIndex } from "./directory.js";
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import { checkCatalog, checkSource } from "./alerts.js";
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// The server checks the university's catalog by itself, not only when a request asks: a
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// republished document is parsed within minutes, the clients' next refresh gets it, and the
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// owner hears about problems (see alerts.js). An unchanged catalog costs two listings. While the
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// university is down, checks reach it less and less often (source.js pauses after failures).
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const INTERVAL = Number(process.env.PSU_WATCH_INTERVAL_MS) || 5 * 60 * 1000;
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/** For /api/health. */
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export const watchStatus = { intervalMinutes: INTERVAL / 60000, lastAt: null, lastError: null };
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let running = null;
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/** One check: the catalog (refreshed), the index of a changed catalog, the messages. */
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export function watchOnce() {
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// A slow university must not stack checks on top of each other.
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running ||= check().finally(() => {
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running = null;
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});
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return running;
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}
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async function check() {
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try {
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const catalog = await getCatalog(true);
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// A failed crawl answers with the saved catalog: nothing new to read or report then.
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if (!catalog.stale) await checkCatalog(await syncIndex(catalog), catalog);
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watchStatus.lastError = catalog.stale ? catalog.error || null : null;
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} catch (error) {
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watchStatus.lastError = error.message;
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}
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await checkSource(catalogFailure());
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watchStatus.lastAt = new Date().toISOString();
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}
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let timer = null;
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/** Checks every few minutes (PSU_WATCH_INTERVAL_MS) for as long as the process runs. */
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export function startWatch() {
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if (timer) return;
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timer = setInterval(watchOnce, INTERVAL);
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timer.unref();
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}
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