{"id":10886,"library":"fibers","title":"Node Fibers","description":"Fibers is a Node.js module that enables cooperative multi-tasking, often referred to as coroutines, by providing an API to jump between multiple call stacks within a single thread. It allows developers to write asynchronous code in a synchronous, blocking style, making it easier to integrate with older synchronous libraries. Originally developed in early 2011 for Node.js v0.1.x, the module's utility has largely been superseded by the standardization of native JavaScript features like Promises, async/await, and Generators. The current stable version is 5.0.3, although its compatibility is limited to Node.js v14.x and older, specifically not supporting v16.0.0 or later due to V8 engine changes. The project maintainer actively recommends avoiding its use due to its obsolescence and the inherent difficulty in maintaining compatibility with the rapidly evolving V8 engine and Node.js platform, which makes its long-term viability uncertain. It does not follow a regular release cadence, with updates primarily driven by critical compatibility fixes for older Node.js versions. A key differentiator was its ability to bring synchronous-looking code to asynchronous environments, a niche now robustly filled by modern JS concurrency primitives. Given its age and the availability of superior native alternatives, it is largely considered a legacy solution.","status":"deprecated","version":"5.0.3","language":"javascript","source_language":"en","source_url":"git://github.com/laverdet/node-fibers","tags":["javascript","fiber","fibers","coroutine","thread","async","parallel","worker","future"],"install":[{"cmd":"npm install fibers","lang":"bash","label":"npm"},{"cmd":"yarn add fibers","lang":"bash","label":"yarn"},{"cmd":"pnpm add fibers","lang":"bash","label":"pnpm"}],"dependencies":[],"imports":[{"note":"Fibers is a CommonJS module and provides the Fiber class as the default export of `require('fibers')`. It does not support ES Modules.","wrong":"import Fiber from 'fibers';","symbol":"Fiber","correct":"const Fiber = require('fibers');"},{"note":"The `yield` operation is a static method of the Fiber class, used to pause the current fiber's execution and return control to the caller. It is not the native JavaScript `yield` keyword.","wrong":"yield;","symbol":"Fiber.yield","correct":"Fiber.yield();"},{"note":"Once a Fiber instance is created, its execution is started or resumed by calling the `.run()` method. Calling the Fiber instance directly as a function will not execute it.","wrong":"myFiber();","symbol":"fiberInstance.run","correct":"myFiber.run();"}],"quickstart":{"code":"const Fiber = require('fibers');\n\nconsole.log('Main thread start');\n\nconst myFiber = Fiber(function() {\n  let counter = 0;\n  while (true) {\n    console.log(`Fiber step ${++counter}`);\n    if (counter >= 3) {\n      console.log('Fiber exiting');\n      break; // Exit the fiber\n    }\n    Fiber.yield(); // Pause fiber, return to caller\n  }\n});\n\nconsole.log('Starting fiber...');\nmyFiber.run(); // Run until first yield or completion\nconsole.log('Back in main thread after first yield');\n\nmyFiber.run(); // Resume fiber\nconsole.log('Back in main thread after second yield');\n\nmyFiber.run(); // Resume fiber\nconsole.log('Back in main thread after third yield');\n\nif (!myFiber.isFinished()) {\n  myFiber.run(); // In case it hasn't finished (e.g., if break condition isn't met)\n}\nconsole.log('Main thread end');","lang":"javascript","description":"Demonstrates the basic usage of `fibers` by creating a fiber, starting its execution, yielding control back to the main thread, and then resuming the fiber multiple times."},"warnings":[{"fix":"Downgrade Node.js to v14.x or earlier, or refactor code to use modern async/await, Promises, or Generators instead of `fibers`.","message":"Fibers is not compatible with Node.js v16.0.0 or later due to breaking changes in the V8 engine, specifically V8 commit dacc2fee0f. Workarounds are non-trivial and unsupported.","severity":"breaking","affected_versions":">=16.0.0"},{"fix":"Migrate existing code to use native async/await, Promises, or Generators, which offer better maintainability, performance, and ecosystem compatibility.","message":"The author of `fibers` actively recommends avoiding its use. The module is considered obsolete, as modern JavaScript features like async/await, Promises, and Generators provide superior, native alternatives for asynchronous control flow.","severity":"deprecated","affected_versions":">=0.1.0"},{"fix":"Ensure the correct `fibers` version is installed for your Node.js runtime. For Node.js v10.x, use `npm install fibers@4`. For v12.x/v14.x, use `npm install fibers@5`.","message":"Specific versions of `fibers` are required for different Node.js major versions. For example, Node.js v10.x requires `fibers@4`, while v12.x and v14.x require `fibers@5`.","severity":"gotcha","affected_versions":"<=14.x"},{"fix":"Install `node-gyp` globally (`npm install -g node-gyp`) and ensure all required build tools are available on your system. Refer to `node-gyp` documentation for platform-specific setup instructions.","message":"`fibers` is a native C++ addon and requires `node-gyp` for compilation. Installation may fail if development tools (Python, C++ compiler, Visual Studio on Windows) are not properly set up, or if V8 ABI changes between Node.js minor versions.","severity":"gotcha","affected_versions":"*"},{"fix":"If using Meteor, uninstall all versions of Node.js and Meteor, then reinstall Meteor to ensure a clean, integrated environment. Do not install `fibers` manually for Meteor projects unless explicitly directed by official Meteor documentation.","message":"Meteor users should generally avoid directly installing `fibers`. Meteor bundles its own compatible version, and manual installation often indicates a misconfiguration or leads to conflicts.","severity":"gotcha","affected_versions":"*"}],"env_vars":null,"last_verified":"2026-04-19T00:00:00.000Z","next_check":"2026-07-18T00:00:00.000Z","problems":[{"fix":"Downgrade your Node.js version to 14.x or earlier, or refactor your application to use native async/await, Promises, or Generators.","cause":"The V8 engine underwent breaking changes in Node.js v16.0.0, which are incompatible with the internal mechanisms of `fibers`.","error":"Fibers is not compatible with nodejs v16.0.0 or later."},{"fix":"Install `node-gyp` globally (`npm install -g node-gyp`) and ensure all required build tools are installed as per `node-gyp` documentation for your operating system. Verify your Node.js version is supported by the `fibers` version you are installing.","cause":"Native compilation of the `fibers` module failed, often due to missing build tools (e.g., Python, C++ compiler) or incompatible Node.js headers.","error":"Error: `node-gyp rebuild` failed with exit code 1"},{"fix":"Run `npm rebuild fibers` to force a recompilation. If it fails, ensure `node-gyp` and build tools are correctly set up. Verify your Node.js version is compatible with the installed `fibers` version.","cause":"The `fibers` native module could not be loaded, typically because compilation failed, or a pre-compiled binary for your specific environment (OS, architecture, V8 version) does not exist.","error":"Cannot find module 'fibers/bin/darwin-x64-v8-XX/fibers.node' (or similar path)"},{"fix":"This often indicates a design issue with using `fibers` for tasks better suited for native async/await or Promises. Consider refactoring your code to avoid `fibers` for memory-intensive operations.","cause":"Using `fibers` in certain complex or long-running scenarios can lead to memory exhaustion due to its native memory management and interaction with V8's garbage collector.","error":"FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory"},{"fix":"Ensure `fibers` is correctly installed via `npm install fibers`. Verify that you are using CommonJS `require` and not ES Module `import`. Check Node.js version compatibility and reinstall if necessary.","cause":"The `require('fibers')` call did not return the expected Fiber class, possibly due to a corrupted installation or an attempt to use it in an incompatible environment.","error":"TypeError: Fiber is not a constructor"}],"ecosystem":"npm"}