Q: You see many connections in the `TIME_WAIT` state on your busy proxy server. Is this an error? What causes it?
TIME_WAIT is not an error; it is a normal part of the TCP teardown process.
🛠️ Production Runbook & Step-by-Step Resolution
Production Solution & Architecture
TIME_WAIT is not an error; it is a normal part of the TCP teardown process. When the server closes a connection (by sending the first FIN packet), it enters the TIME_WAIT state for a period (usually 2 * MSL, around 60 seconds). This ensures that any delayed packets floating in the network are dropped and don't accidentally corrupt a new connection that happens to reuse the exact same source IP and port. However, on a very busy proxy, too many TIME_WAIT sockets can exhaust ephemeral ports, preventing new outbound connections. It can be mitigated by keeping connections alive longer (connection pooling), or tuning sysctl (tcp_tw_reuse=1 to safely reuse them for outbound connections).
- Immediate Triage: TIME_WAIT is not an error; it is a normal part of the TCP teardown process.
- Run targeted verification commands before modifying configuration.
- Automate permanent guardrails (CI check, alerts, IaC policy) to prevent recurrence.