346111250e
Before this change, `promises.timesLimit()` created `concurrency - 1`
too many promises. The only users of this function use a concurrency
of 500, so this meant that 499 extra promises were created each time
it was used. The bug didn't affect correctness, but it did result in a
large number of unnecessary database operations whenever a pad was
deleted. This change fixes that bug.
Also:
* Convert the function to async and have it resolve after all of the
created promises are resolved.
* Reject concurrency of 0 (unless total is 0).
* Document the function.
* Add tests.
85 lines
2.6 KiB
JavaScript
85 lines
2.6 KiB
JavaScript
function m(mod) { return __dirname + '/../../../src/' + mod; }
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const assert = require('assert').strict;
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const promises = require(m('node/utils/promises'));
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describe('promises.timesLimit', async () => {
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let wantIndex = 0;
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const testPromises = [];
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const makePromise = (index) => {
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// Make sure index increases by one each time.
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assert.equal(index, wantIndex++);
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// Save the resolve callback (so the test can trigger resolution)
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// and the promise itself (to wait for resolve to take effect).
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const p = {};
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const promise = new Promise((resolve) => {
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p.resolve = resolve;
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});
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p.promise = promise;
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testPromises.push(p);
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return p.promise;
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};
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const total = 11;
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const concurrency = 7;
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const timesLimitPromise = promises.timesLimit(total, concurrency, makePromise);
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it('honors concurrency', async () => {
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assert.equal(wantIndex, concurrency);
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});
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it('creates another when one completes', async () => {
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const {promise, resolve} = testPromises.shift();
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resolve();
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await promise;
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assert.equal(wantIndex, concurrency + 1);
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});
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it('creates the expected total number of promises', async () => {
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while (testPromises.length > 0) {
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// Resolve them in random order to ensure that the resolution order doesn't matter.
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const i = Math.floor(Math.random() * Math.floor(testPromises.length));
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const {promise, resolve} = testPromises.splice(i, 1)[0];
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resolve();
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await promise;
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}
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assert.equal(wantIndex, total);
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});
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it('resolves', async () => {
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await timesLimitPromise;
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});
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it('does not create too many promises if total < concurrency', async () => {
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wantIndex = 0;
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assert.equal(testPromises.length, 0);
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const total = 7;
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const concurrency = 11;
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const timesLimitPromise = promises.timesLimit(total, concurrency, makePromise);
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while (testPromises.length > 0) {
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const {promise, resolve} = testPromises.pop();
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resolve();
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await promise;
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}
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await timesLimitPromise;
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assert.equal(wantIndex, total);
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});
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it('accepts total === 0, concurrency > 0', async () => {
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wantIndex = 0;
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assert.equal(testPromises.length, 0);
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await promises.timesLimit(0, concurrency, makePromise);
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assert.equal(wantIndex, 0);
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});
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it('accepts total === 0, concurrency === 0', async () => {
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wantIndex = 0;
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assert.equal(testPromises.length, 0);
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await promises.timesLimit(0, 0, makePromise);
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assert.equal(wantIndex, 0);
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});
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it('rejects total > 0, concurrency === 0', async () => {
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await assert.rejects(promises.timesLimit(total, 0, makePromise), RangeError);
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});
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});
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