This would be a Denial of Service attack. Security: If it is possible that for certain input one of your threads might block, a malicious client could submit this 'evil input', make your threads block, and keep them from working on other clients.Performance: If you regularly perform heavyweight activity on either type of thread, the throughput (requests/second) of your server will suffer.This provides two motivations for blocking neither the Event Loop nor the Worker Pool: While a thread is blocked working on behalf of one client, it cannot handle requests from any other clients. If a thread is taking a long time to execute a callback (Event Loop) or a task (Worker), we call it 'blocked'. In Node.js there are two types of threads: one Event Loop (aka the main loop, main thread, event thread, etc.), and a pool of k Workers in a Worker Pool (aka the threadpool). Node.js uses a small number of threads to handle many clients. Why should I avoid blocking the Event Loop and the Worker Pool? This applies to callbacks on the Event Loop and tasks on the Worker Pool. Node.js is fast when the work associated with each client at any given time is 'small'. Here's a good rule of thumb for keeping your Node.js server speedy: If Node.js can make do with fewer threads, then it can spend more of your system's time and memory working on clients rather than on paying space and time overheads for threads (memory, context-switching).īut because Node.js has only a few threads, you must structure your application to use them wisely. The secret to the scalability of Node.js is that it uses a small number of threads to handle many clients. Node.js scales well, sometimes better than more heavyweight approaches like Apache. Node.js runs JavaScript code in the Event Loop (initialization and callbacks), and offers a Worker Pool to handle expensive tasks like file I/O.

Where OS-specific details vary, this document is Linux-centric. This document is written with Node.js servers in mind, but the concepts apply to complex Node.js applications as well. If you're writing anything more complicated than a brief command-line script, reading this should help you write higher-performance, more-secure applications. Don't Block the Event Loop (or the Worker Pool) Should you read this guide?

Node js thread sleep