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b76f1f166b
The reason for refactoring was to accommodate Multiseis / client sequence exports, which will be served by this endpoint via a specific Content-Type. In the process, the cache has been fixed and redesigned. Related to #12.
84 lines
2.1 KiB
JavaScript
84 lines
2.1 KiB
JavaScript
const { listen } = require('../../../ws/db');
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// Event responses take a long time as we are querying a view
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// which is the union of other views and non-optimised tables,
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// so to speed things up a bit for the user we cache the
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// results here.
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// We do this by indexing each result by its ETag value and
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// storing the ID of the project it belongs to as well as the
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// timestamp of the request. If the events for a project are
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// modified in any way (addition/deletion/change) we immediately
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// invalidate all cached responses for that project, else we
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// delete them when they're older than maxAge (plus a delay).
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// When the user sends a request with an ETag, we search for
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// the ETag in our cache and return that, if present, instead
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// of hitting the database.
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const cache = {};
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const maxAge = 90*60*1000; // 1.5 hours
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setInterval(() => {
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const now = Date.now();
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for (const key in cache) {
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const value = cache[key];
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if ((now - value.tstamp) > maxAge) {
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// console.log("CLEARING", key);
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delete cache[key];
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}
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}
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}, 5*60*1000); // Run every five minutes
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listen(["event"], (data) => {
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for (const key in cache) {
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const value = cache[key];
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if (value.pid == data.payload.pid) {
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delete cache[key];
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}
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}
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});
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function get (req, res, next) {
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try {
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// console.log(cache);
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const etag = req.get('if-none-match');
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// console.log("ETag", etag);
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if (etag && cache[etag]) {
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// console.log("In cache");
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if (cache[etag].headers) {
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for (const header in cache[etag].headers) {
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const value = cache[etag].headers[header];
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if (header && value) {
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res.set(header, value);
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}
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}
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}
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// 304s have no body
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// https://tools.ietf.org/html/rfc7232#section-4.1
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res.status(304).send();
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next('route');
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} else {
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// console.log("Not in cache");
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next();
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}
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} catch (err) {
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next(err);
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}
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}
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function save (req, res, next) {
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const etag = res.getHeader("etag");
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if (etag) {
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cache[etag] = {
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headers: {
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"Content-Type": res.getHeader("content-type") || "application/json"
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},
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pid: req.params.project,
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tstamp: Date.now()
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}
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// console.log("CACHE", cache);
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}
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next();
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}
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module.exports = { get, save };
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