Deeply analyze the agent layer root cause of 502 error, explain the causes of timeout, resource exhaustion and process crash in Nginx and PHP-FPM collaboration, and provide professional diagnosis ideas.

This article clearly analyzes the fundamental difference between the two common gateway errors 502 and 504. The article provides from checking server logs, restarting services to optimize the code and database query the complete path of investigation, and especially for WordPress site plug-ins and theme conflict solution ...