This guide explains the distinct causes of 502 Bad Gateway, 504 Gateway Timeout, and Connection Reset errors in Nginx reverse‑proxy setups and provides a step‑by‑step, four‑segment troubleshooting workflow with concrete log examples, shell commands, and configuration recommendations.
This guide explains how to distinguish the root causes of 502 Bad Gateway, 504 Gateway Timeout, and Connection Reset errors in Nginx reverse‑proxy deployments and provides a step‑by‑step, four‑segment troubleshooting workflow with concrete log patterns, shell commands, and configuration tweaks.
The article explains that during TCP's three‑way handshake, if a client receives a SYN‑ACK with an unexpected acknowledgment number, it must send an RST to abort the stale connection, because silently discarding the packet would cause long retransmission delays and prevent the new connection from being established.
This article details a production incident where a Go backend service returned "connection reset by peer" due to exhausted process file descriptors caused by a saturated database connection pool, and describes the step‑by‑step troubleshooting, socket internals, and the eventual fix.
