help wantedstaletimers
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Description
- Version: v8.15.1
- Platform: Darwin Charlies-MacBook-Pro.local 18.2.0 Darwin Kernel Version 18.2.0: Thu Dec 20 20:46:53 PST 2018; root:xnu-4903.241.1~1/RELEASE_X86_64 x86_64
I have the following code in Node.js.
const timeout = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
I'm trying to test this code with the following test:
it("Should wait for given time before resolving", async () => {
const MS = 100;
const start = process.hrtime();
await timeout(MS);
const diff = process.hrtime(start);
expect(((diff[0] * NS_PER_SEC) + diff[1]) / 1000000).to.at.least(MS);
});
The problem is sometimes (rarely), this test fails:
Should wait for given time before resolving:
AssertionError: expected 99.595337 to be at least 100
+ expected - actual
-99.595337
+100
Obviously this is some type of timing issue with Node.js or something. If anything I expect await timeout(MS); to take slightly longer than MS. In no case do I expect it to take less time.
What is it about the internals of JavaScript/Node.js that causes this to happen?
This occurred on macOS 10.14.3 running Node.js version 8.15.1.