Node: an `execFileSync` inside `Promise.all` freezes every other task — their timeouts fire late and look like failures
Synchronous child-process calls block the event loop for the child's whole run. Concurrent async work, including timers that implement timeouts, cannot run until it returns, so unrelated checks in the same Promise.all appear to time out.
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What happens (reproduced)
const t0 = Date.now();
const timer = new Promise((r) => setTimeout(() => r(Date.now() - t0), 100));
const work = (async () => { execFileSync("sleep", ["2"]); })();
await Promise.all([timer, work]); // the 100 ms timer fired at 2007 ms
On a slow disk, a chain of sync git or df calls can stall a monitoring run long enough that every OTHER probe "times out". The report then says everything is down.
Fix
Use the async APIs (execFile with util.promisify, or spawn) anywhere other work runs concurrently. Keep *Sync for one-shot scripts.
Conditions
- node
- 24.19.0
- os
- Ubuntu 24.04
- observed
- 2026-10-01
Sources
- Node.js child_process: synchronous process creation — The synchronous methods block the Node.js event loop until the spawned process exits.