{"id":24070,"date":"2019-02-19T12:15:46","date_gmt":"2019-02-19T10:15:46","guid":{"rendered":"https:\/\/www.webcodegeeks.com\/?p=24070"},"modified":"2019-02-19T11:31:08","modified_gmt":"2019-02-19T09:31:08","slug":"using-node-11-7-worker-threads-rxjs","status":"publish","type":"post","link":"https:\/\/www.webcodegeeks.com\/javascript\/node-js\/using-node-11-7-worker-threads-rxjs\/","title":{"rendered":"Using Node 11.7 Worker Threads with RxJS Observable"},"content":{"rendered":"\n

With the release of Node 11.7, the worker_threads module becomes a standard feature and is no longer hidden behind the --experimental-worker<\/code> switch. The worker_threads module allows developers to run JavaScript asynchronously in light-weight, isolated threads contained within the main Node process. This article will be focusing on how use worker threads to execute a task asynchronously and stream data from that task back to the rest of your Node application using RxJS Observables.<\/p>\n\n\n\n

With the release of Node 11.7, the worker_threads module becomes a standard feature and is no longer hidden behind the --experimental-worker<\/code> switch. The worker_threads module allows developers to run JavaScript asynchronously in light-weight, isolated threads contained within the main Node process. This article will be focusing on how use worker threads to execute a task asynchronously and stream data from that task back to the rest of your Node application using RxJS Observables.<\/p>\n\n\n\n

Before we get started, if you want to learn more about worker threads and why you might want to use them, I would recommend reading Node.js multithreading: What are Worker Threads and why do they matter?<\/a> by Alberto Gimeno.<\/a> Alberto has done a fantastic job explaining the purpose of the worker_thread module, provided some solid examples of where it makes sense to use it as well as demonstrated some alternate ways to build a multi-threaded Node app.<\/p>\n\n\n\n

What are we building?<\/h2>\n\n\n\n

We are going to be building a simple Node app that creates a worker thread running a simulated long-running task that reports status back at regular intervals until it completes or until time runs out. The worker thread will be wrapped in an RxJS Observable so that the rest of the application can stream messages returned from the worker thread using the powerful RxJS library.<\/p>\n\n\n\n

If you want to jump ahead and see the final solution, you can see it out on GitHub at briandesousa\/node-worker-thread-rxjs<\/a>.<\/strong><\/p>\n\n\n\n

Setting up your environment<\/h2>\n\n\n\n

The first thing we need to do is ensure our environment is ready to go:<\/p>\n\n\n\n

  1. Install Node 11.7.0+<\/li>
  2. Use npm init<\/code> to initialize a new NPM package<\/li>
  3. Add a simple start script to the package.json to start the app: node node-parent-thread-rxjs.js<\/code><\/li>
  4. Install the RxJS package with npm install -s rxjs<\/code><\/li>
  5. Create node-parent-thread-rxjs.js which will contain code running on the main thread<\/li>
  6. Create node-worker-thread-rxjs.js which will contain the implementation of the long-running task running on a separate thread<\/li><\/ol>\n\n\n\n

    Creating the worker thread<\/h2>\n\n\n\n

    The worker thread has the logic to simulate a long-running task:<\/p>\n\n\n\n

    \nconst { workerData, parentPort } = require('worker_threads');\n\nparentPort.postMessage(`starting heavy duty work from process ${process.pid} that will take ${workerData}s to complete`);\n\ntimeLimit = workerData;\ntimer = 0;\n\n\/\/ simulate a long-running process with updates posted back on a regular interval\ndo {\n    setTimeout(\n        (count) => {\n            parentPort.postMessage(`heavy duty work in progress...${count + 1}s`);\n            if (count === timeLimit) {\n                parentPort.postMessage('done heavy duty work');\n            }\n        },\n        1000 * timer,\n        timer);\n} while (++timer !== timeLimit);\n<\/pre>\n\n\n\n
    Let\u2019s break this script down a bit:<\/p>\n\n\n\n