![]() When the main thread later inspects the data, it sees the changes written by the worker. This works because the worker thread can access the shared memory region created by the main thread. There is an exception to this rule: you can use a SharedArrayBuffer to directly share memory between the threads by specifically allocating it as shared memory: Variables set on one side aren't visible to the other. ![]() The postMessage() function is used to send data to the opposite end of the main-worker thread divide. This code, which you looked at in detail in part one, creates a worker process that receives a value ( hello) from the main thread and sends it back in a different form ( You said "hello".). Since the file is executed as a child process, there's no implicit memory sharing between the main program and the worker "thread." Instead, an event-based messaging system is provided so values can be exchanged between the processes.ฤก0 const worker = new Worker(_filename, \".` ) The new runtime can then be used to execute a JavaScript file out of the main event loop. They work by spawning an isolated instance of Node's V8 JavaScript runtime. Node.js worker threads spawn child processes that operate independently of the JavaScript code in the main process. In this scenario, memory updated in one thread will be visible to the others, and implementing multithreaded code requires careful memory management to prevent race conditions. Truly multithreaded applications allow the concurrent execution of multiple threads that share the same state. The first and most prominent restriction of worker threads is that they aren't real threads in the conventional sense. You need to be aware of these before you start implementing your workers, as some situations shouldn't be parallelized with this mechanism. The module and the concept it implements come with several caveats though. CPU-intensive operations, background processing, and any parallel code execution other than async I/O will need to be implemented using worker threads. The benefits of worker threads can be easily summarized: They're the only way to get something similar to multithreading when you're programming with Node.js. We'll also tour five prominent libraries that make the worker_threads module easier to use. In this article, we'll look at the pitfalls of worker threads and how they differ from the multithreading implementations in other programming languages. In a previous post, you learned what worker threads are, their common use cases, and how to add them to your project. The worker_threads module addresses this problem by providing a mechanism for running code in parallel using a form of threading. ![]() Node.js presents a single-threaded event loop to your application, which allows CPU-bound operations to block the main thread and create delays.
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