65 lines
2.2 KiB
JavaScript
65 lines
2.2 KiB
JavaScript
'use strict';
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const ONE_MINUTE_IN_SECONDS = 60;
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const THREE_MINUTE_IN_SECONDS = 60 * 3;
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const FIVE_MINUTES_IN_SECONDS = ONE_MINUTE_IN_SECONDS * 5;
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const TEN_MINUTES_IN_SECONDS = ONE_MINUTE_IN_SECONDS * 10;
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const FIFTEEN_MINUTES_IN_SECONDS = ONE_MINUTE_IN_SECONDS * 15;
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const THIRTY_MINUTES_IN_SECONDS = ONE_MINUTE_IN_SECONDS * 30;
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const ONE_HOUR_IN_SECONDS = ONE_MINUTE_IN_SECONDS * 60;
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const ONE_YEAR_IN_SECONDS = ONE_HOUR_IN_SECONDS * 24 * 365;
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const defaultCacheTTL = {
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ttl: ONE_YEAR_IN_SECONDS,
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fallbackTtl: FIVE_MINUTES_IN_SECONDS
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};
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const validFallbackTTL = [
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ONE_MINUTE_IN_SECONDS,
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THREE_MINUTE_IN_SECONDS,
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FIVE_MINUTES_IN_SECONDS,
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TEN_MINUTES_IN_SECONDS,
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FIFTEEN_MINUTES_IN_SECONDS,
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THIRTY_MINUTES_IN_SECONDS,
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ONE_HOUR_IN_SECONDS
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];
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const { ttl, fallbackTtl } = Object.assign(defaultCacheTTL, global.settings.cache);
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module.exports = function cacheControlHeader () {
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if (!validFallbackTTL.includes(fallbackTtl)) {
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throw new Error(`Invalid fallback TTL value for Cache-Control header. Got ${fallbackTtl}, expected ${validFallbackTTL.join(', ')}`);
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}
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return function cacheControlHeaderMiddleware (req, res, next) {
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const { cachePolicy } = res.locals.params;
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const { affectedTables, mayWrite } = res.locals;
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if (cachePolicy === 'persist') {
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res.header('Cache-Control', `public,max-age=${ONE_YEAR_IN_SECONDS}`);
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return next();
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}
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if (affectedTables && affectedTables.getTables().every(table => table.updated_at !== null)) {
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const maxAge = mayWrite ? 0 : ttl;
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res.header('Cache-Control', `no-cache,max-age=${maxAge},must-revalidate,public`);
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return next();
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}
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const maxAge = fallbackTtl;
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res.header('Cache-Control', `no-cache,max-age=${computeNextTTL({ ttlInSeconds: maxAge })},must-revalidate,public`);
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return next();
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};
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};
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function computeNextTTL ({ ttlInSeconds } = {}) {
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const nowInSeconds = Math.ceil(Date.now() / 1000);
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const secondsAfterPreviousTTLStep = nowInSeconds % ttlInSeconds;
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const secondsToReachTheNextTTLStep = ttlInSeconds - secondsAfterPreviousTTLStep;
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return secondsToReachTheNextTTLStep;
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}
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