The Process That Kept Dying: A memory leak murder mystery (node)

The article narrates the investigation of a recurring 502 Bad Gateway error affecting a crowdfunding site, led by an SRE named Charlie and a detective figure. The detective begins by analyzing the situation, noting that the errors have been occurring intermittently since June, primarily linked to the Next.js application. Initial suspicions fall on PM2, a process manager for Node.js, which was found to be restarting processes due to memory limits. Despite adjusting the PM2 configuration, the errors persisted, indicating a deeper issue—a memory leak in the application.

The detective outlines a systematic approach to identify the leak, involving debugging, taking heap snapshots, and load testing. After several attempts, the detective discovers that Moment.js, a date manipulation library, was responsible for the memory leak due to calls to moment.updateLocale. An update from version 2.24.0 to 2.29.4 of Moment.js resolves the issue, eliminating the 502 errors.

The narrative emphasizes the challenges of debugging memory leaks and the importance of thorough investigation and systematic troubleshooting in software development. The case concludes with a sense of relief as the immediate problem is resolved, but the detective acknowledges that more challenges lie ahead in the ever-evolving tech landscape.