LINUX: Debugging Tip: How to Know Whether The PID, File Descriptor Is Stale?

When a PID and associated file description is stale, following are the symptoms we see

• Any connections to the listen address will fail with connected refused messages.
• Restarting the app process, the PID is not cleared and app process or container instances fails with bind address already in use message.
• strace -p <PID> command shows that there is no activity on the PID. We may also see messages that the process is detached.

Keywords

PID state zombie process process id PID FD filedescriptor file descriptor file-descriptor cleanup clear clearing