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28c7394319
PR-URL: https://github.com/nodejs/node/pull/55063 Reviewed-By: Filip Skokan <panva.ip@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
66 lines
2.1 KiB
JavaScript
66 lines
2.1 KiB
JavaScript
'use strict';
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// Test to validate massive dns lookups do not block filesystem I/O
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// (or any fast I/O). Prior to https://github.com/libuv/libuv/pull/1845
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// few back-to-back dns lookups were sufficient to engage libuv
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// threadpool workers in a blocking manner, throttling other work items
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// that need pool resources. Start slow and fast I/Os together, make sure
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// fast I/O can complete in at least in 1/100th of time for slow I/O.
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// TEST TIME TO COMPLETION: ~5 seconds.
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const common = require('../common');
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const dns = require('dns');
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const fs = require('fs');
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const assert = require('assert');
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const start = Date.now();
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const slowIOmax = 100;
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let slowIOcount = 0;
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let fastIOdone = false;
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let slowIOend, fastIOend;
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function onResolve() {
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slowIOcount++;
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if (slowIOcount === slowIOmax) {
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slowIOend = Date.now();
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// Conservative expectation: finish disc I/O
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// at least by when the net I/O completes.
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assert.ok(fastIOdone,
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'fast I/O was throttled due to threadpool congestion.');
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// More realistic expectation: finish disc I/O at least within
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// a time duration that is half of net I/O.
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// Ideally the slow I/O should not affect the fast I/O as those
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// have two different thread-pool buckets. However, this could be
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// highly load / platform dependent, so don't be very greedy.
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const fastIOtime = fastIOend - start;
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const slowIOtime = slowIOend - start;
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const expectedMax = slowIOtime / 2;
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assert.ok(fastIOtime < expectedMax,
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'fast I/O took longer to complete, ' +
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`actual: ${fastIOtime}, expected: ${expectedMax}`);
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}
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}
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for (let i = 0; i < slowIOmax; i++) {
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// We need to refresh the domain string everytime,
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// otherwise the TCP stack that cache the previous lookup
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// returns result from memory, breaking all our Math.
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dns.lookup(`${randomDomain()}.com`, {}, common.mustCall(onResolve));
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}
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fs.readFile(__filename, common.mustCall(() => {
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fastIOend = Date.now();
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fastIOdone = true;
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}));
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function randomDomain() {
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const d = Buffer.alloc(10);
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for (let i = 0; i < 10; i++)
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d[i] = 97 + (Math.round(Math.random() * 13247)) % 26;
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return d.toString();
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}
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