This article presents a detailed methodology for testing Linux servers to handle 1 million concurrent TCP connections using the epoll I/O event notification facility. It begins with essential kernel parameter adjustments, such as increasing the maximum number of open file descriptors and tuning network stack settings like net.ipv4.tcp_mem and net.core.somaxconn. The author then explains how to configure the epoll-based client to create and manage a large number of connections efficiently, including handling non-blocking sockets and edge-triggered events. Practical tips on avoiding common pitfalls like port exhaustion and memory limits are also provided. This guide is invaluable for backend engineers and SREs working on high-concurrency systems, offering a clear path to validate server capacity under extreme load.
A practical guide to stress-testing Linux servers for 1M concurrent connections using epoll, covering kernel tuning, fd limits, and client design.