Ungraceful shutdown of mysql-router-exporter can lead to connections in TIME_WAIT; missing graceful shutdown of server

[shayancanonical]

Issue

The exporter starts a server on listen-port using http.ListenAndServe. However, there is no attempt at a graceful shutdown when a SIGTERM is received (see this post for some ideas of how a SIGTERM can be reacted with a server.Shutdown())

We have an issue in our project where we use this project (mysqlrouter_exporter). As the trace in the issue indicates, we run into bind address in use error intermittently when we start exporter, stop it and then restart it. Further digging revealed that when we stop exporter, sometimes, due to an ungraceful shutdown, we have connections in TIME_WAIT:

root@mysql-router-k8s-0:/# netstat -nat  | grep 49152
tcp        0      0 10.1.241.229:49152      10.1.241.230:3306       TIME_WAIT

It is exactly under these conditions that we run into the bind address in use error. When the

Suggested Solution

To gracefully shutdown the server as indicated by the above linked post when a SIGTERM is received

Potential followups

I will attempt to create a PR with a proposed solution for this issue

[rluisr]

@shayancanonical Thank you for reporting.

I released a new version v5.0.1. If the problem has not been resolved, re-open it.