A systematic troubleshooting guide for Nginx 502 Bad Gateway errors covering six root-cause areas: upstream process/socket issues, config mismatches, permission blocks, application crashes/timeouts, DNS/TCP upstream problems, and host resource exhaustion — with exact commands, config snippets, and a ready-to-run evidence collection script.
When Nginx returns a 502 Bad Gateway, the article walks through six systematic investigation directions—preserving evidence, checking upstream processes and sockets, validating configuration, verifying permissions, examining upstream timeouts, DNS resolution, and host resource limits—using concrete commands and log analysis to pinpoint the root cause.
Go 1.26 introduces context‑aware net.Dialer methods that combine the zero‑overhead speed of net.DialTCP with timeout, cancellation and tracing capabilities, eliminating DNS resolution and protocol dispatch overhead while providing clear code and a 10‑15% latency reduction for high‑frequency short connections.
This article demonstrates how to use the junixsocket library to add Unix domain socket support to Java applications, providing Maven dependency details, full server and client code examples, and cross‑language testing with a Go server implementation.
This article explains how PHP‑FPM and Nginx interact via FastCGI, detailing the roles of master and worker processes, configuration directives, and the differences between TCP and Unix socket communication methods.
This article explains how to achieve graceful, zero‑downtime restarts for long‑living TCP services by passing open file descriptors through a Unix domain socket, allowing new processes to inherit existing connections without interrupting clients, and provides a complete Go demo implementation.
