Workers and Test Runners

Guidance for multi-threaded Node apps and test frameworks.

Worker Threads (Node)

• Create one logger per worker (each has its own VM context).
• If you need deterministic ordering across workers, aggregate logs in the main thread:

// worker.js
import spec from 'spectrallogs';
import { parentPort } from 'worker_threads';

const log = spec.child('w1');
function emit(level, msg) {
  parentPort.postMessage({ level, msg });
}

emit('info', 'ready');

// main.js
import spec from 'spectrallogs';
import { Worker } from 'worker_threads';

const main = spec.child('main');
const worker = new Worker('./worker.js');

worker.on('message', ({ level, msg }) => {
  (main)[level](msg); // writes through a single sink
});

Notes:

• This preserves order at the aggregation point and avoids interleaved stdout from multiple writers.
• You may also route to a file or IPC plugin if preferred.

Test Runners (Vitest/Jest/Mocha)

• Runners capture/wrap stdout; buffering can change interleaving.
• Recommendations:
  • In CI, disable colors for clean logs.
  • For strict interleaving, disable buffering: spec.configure({ bufferWrites: false }).
  • When runners aggressively capture output, consider a custom sink (file plugin, or redirect to a buffer and print at the end).

Web Test Environments (JSDOM, Playwright)

• Use spectrallogs/web.
• For heavy logs, batch or provide a DOM sink to avoid DevTools overhead:

import { SpectralLoggerWeb } from 'spectrallogs/web';
const sink = (args: any[]) => console.log(...args);
const logger = new SpectralLoggerWeb({ batching: true, sink });