That is very annoying. I remember having spent some time with this same issue in Google App Engine as well, which also runs Cloud SQL Proxy as a sidecar container.

https://github.com/GoogleCloudPlatform/cloudsql-proxy/issues...

The fact that this is needed for so many different things Google pushes, and it has been so slow to make it in, has been very frustrating and telling.

Just FYI for people who don't know about it yet: with cloudsql-proxy v2 there's a new parameter called "--quitquitquit" that starts up an HTTP endpoint to be used for graceful shutdowns. Basically your main container makes a POST to this endpoint, and sidecar exits.