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Lint multiple files in parallel [$500]

Freshabout 22 hours ago

Mar 14, 20260 views

Confidence Score95%

95%

Problem

This is a discussion issue for adding ability to run eslint in parallel for multiple files. The idea is that ESLint is mostly CPU bound, not IO bound, so creating multiple threads (for machine with multiple cores) might (and probably will) increase performance in a meaningful way. The downside is that currently ESLint's codebase is synchronous. So this would require rewriting everything up to and including eslint.js to be asynchronous, which would be a major effort. I played with this a little while ago and found a few libraries for Node that handle thread pool, including detection of number of cores available on the machine. - Node-threads-a-gogo - seems pretty good, but looks dead. - nPool - seems actively in development, but has native components (C++) - Node WebWorkers - seems pretty dead too. - Parallel - seems dead, and no pool implementation. - Node Clusters - not stable yet, and probably isn't going to be available on Node v0.10 - WebWorkers - seems that they are only implemented in io.js And there are a ton of other libraries out there for this. If anyone had any experience writing multithreaded applications for node.js and would like to suggest alternatives or comment on the above list, please feel free. P.S. https://www.airpair.com/javascript/posts/which-async-javascript-libraries-should-i-use <bountysource-plugin> Want to back this issue? Post a bounty on it! We accept bounties via Bountysource. </bountysource-plugin>

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2 Fixes

Canonical Fix

Unverified Fix

New Fix – Awaiting Verification

Implement Parallel Linting in ESLint Using Worker Threads

Medium Risk

ESLint's synchronous codebase limits performance on multi-core machines, as it does not utilize parallel processing capabilities. This results in inefficient CPU usage during linting tasks, especially for large codebases.

Awaiting Verification

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1
Install Worker Threads
Add the 'worker_threads' module to your ESLint project to enable parallel processing. This module allows you to create threads that can run JavaScript operations concurrently.
bash
```
npm install worker_threads
```

Refactor ESLint Linting Function

Modify the existing linting function to utilize worker threads. This involves creating a worker for each file to be linted, allowing multiple files to be processed simultaneously.

javascript

const { Worker } = require('worker_threads');

function lintFile(filePath) {
  return new Promise((resolve, reject) => {
    const worker = new Worker('./lintWorker.js', { workerData: filePath });
    worker.on('message', resolve);
    worker.on('error', reject);
    worker.on('exit', (code) => {
      if (code !== 0) reject(new Error('Worker stopped with exit code ' + code));
    });
  });
}

Create Lint Worker Script

Create a separate worker script (lintWorker.js) that will handle the linting process for each file. This script should import ESLint and execute the linting logic.

javascript

const { workerData, parentPort } = require('worker_threads');
const { ESLint } = require('eslint');

(async () => {
  const eslint = new ESLint();
  const results = await eslint.lintFiles(workerData);
  parentPort.postMessage(results);
})();

4
Modify Main Linting Logic
Update the main linting logic to distribute file paths across multiple workers based on the number of CPU cores available. Use the 'os' module to determine the number of cores.
javascript
```
const os = require('os');
const numCPUs = os.cpus().length;

async function lintFiles(filePaths) {
  const promises = filePaths.map((filePath) => lintFile(filePath));
  return Promise.all(promises);
}
```
5
Test Parallel Linting
Run the modified ESLint on a sample project with multiple files to ensure that the parallel linting works correctly and improves performance. Monitor CPU usage and linting time.
bash
```
node your-eslint-script.js
```

Validation

Confirm that the linting process completes successfully for multiple files and that the performance (time taken) is improved compared to the previous synchronous implementation. Check CPU usage to ensure multiple cores are being utilized.

1 low-confidence fix

Unverified Fix

New Fix – Awaiting Verification

Implement ESLint Parallel Linting Using Worker Threads

Medium Risk

ESLint's synchronous codebase limits its ability to utilize multiple CPU cores effectively, leading to performance bottlenecks when linting multiple files. By rewriting ESLint to leverage Node.js Worker Threads, we can achieve parallel processing, significantly improving linting performance on multi-core systems.

Awaiting Verification

Be the first to verify this fix

1
Set Up Worker Threads
Install the required dependencies for using Worker Threads in Node.js. This will allow us to create multiple threads for linting files in parallel.
bash
```
npm install worker_threads
```

Create Worker Script

Create a separate JavaScript file (e.g., `lintWorker.js`) that will handle the linting of individual files. This script will receive file paths from the main thread, run ESLint on them, and return the results.

javascript

const { parentPort } = require('worker_threads');
const { ESLint } = require('eslint');

const eslint = new ESLint();

parentPort.on('message', async (filePath) => {
  const results = await eslint.lintFiles(filePath);
  parentPort.postMessage(results);
});

Modify Main Linting Logic

Update the main ESLint script to spawn multiple worker threads based on the number of CPU cores available. Distribute the file paths among these workers for parallel processing.

javascript

const { Worker, isMainThread, parentPort } = require('worker_threads');
const os = require('os');
const path = require('path');

if (isMainThread) {
  const files = ['file1.js', 'file2.js', ...]; // List of files to lint
  const numCPUs = os.cpus().length;
  const workers = [];

  for (let i = 0; i < numCPUs; i++) {
    const worker = new Worker(path.resolve(__dirname, 'lintWorker.js'));
    workers.push(worker);
    worker.on('message', (result) => {
      console.log(result);
    });
    worker.postMessage(files[i]); // Send file path to worker
  }
}

4
Handle Worker Results
Implement logic to aggregate results from all worker threads and handle any errors that may occur during linting. This ensures that the main thread can report the final linting results accurately.
javascript
```
let results = [];
workers.forEach(worker => {
  worker.on('message', (result) => {
    results.push(result);
    // Optionally, check for completion and handle final results
  });
});
```
5
Test and Validate
Run the modified ESLint script on a project with multiple files to confirm that linting occurs in parallel and performance improvements are observed. Monitor CPU usage to ensure multiple cores are utilized.
bash
```
node your-eslint-script.js
```

Validation

Confirm that the ESLint runs complete faster than the previous synchronous implementation. Monitor CPU usage to ensure multiple cores are being utilized effectively during the linting process.

Environment

Submitted by

Alex Chen

2450 rep

Lint multiple files in parallel [$500]

Problem

2 Fixes

Implement Parallel Linting in ESLint Using Worker Threads

Install Worker Threads

Refactor ESLint Linting Function

Create Lint Worker Script

Modify Main Linting Logic

Test Parallel Linting

Validation

Implement ESLint Parallel Linting Using Worker Threads

Set Up Worker Threads

Create Worker Script

Modify Main Linting Logic

Handle Worker Results

Test and Validate

Validation

Environment

Submitted by

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