How can I tell if a Node.js operation uses the thread pool?
Network-related operations typically use the OS's async I/O directly. File system, system DNS (dns.lookup), and certain crypto operations typically use the thread pool. The Node.js docs and libuv source are the authoritative references.
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More FAQs in Which Node.js Operations Use the libuv Thread Pool?
File system operations (fs module), DNS lookups (dns.lookup), some crypto operations (crypto.pbkdf2, crypto.scrypt), and some zlib operations. Network I/O does not use the thread pool; it uses the OS's async capabilities directly.
No. Network I/O (TCP, UDP, HTTP) uses the OS's async APIs directly through libuv, which is why Node.js handles thousands of network connections efficiently without using the 4 default thread pool threads.
Because the OS provides reliable async APIs for network I/O, so libuv uses those directly. For file systems, the OS does not provide reliable async APIs on all platforms, so libuv uses the thread pool to avoid blocking the main thread.
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