query frontend doesn't stop cache on exit

[dmitsh]

When the query frontend exits, it does not invoke Stop method of Cache interface.

[bboreham]

What are the bad consequences of this?

[dmitsh]

What are the bad consequences of this?

In case of memcached, we will have updateLoop go-routine running indefinitely.
In case of Redis (#1612) we won't properly clean up and close connection pool.

[bboreham]

You’re saying the updateLoop continues running past the process’ decision to exit?

[dmitsh]

You’re saying the updateLoop continues running past the process’ decision to exit?

No, when a process exits, obviously all running go-routines belonging to that process are terminated.
What I'm saying is that Stop method in Cache interface is never called, despite being declared.
We might need to gracefully stop the cache before exiting.

[bboreham]

Ok, I like to be precise.
So the issue is that there are no bad consequences but there might be, under some different circumstances in future?

[dmitsh]

You are correct. There are no immediate consequences. There is a bug in memcached_client.go, which I submitted PR #1610 for, but since Stop is never called, this bug hasn't been exposed.

I've been working on adding Redis cache support (PR #1612), and for that case calling Stop would be desirable, as it would properly dispose connection pool.

[bboreham]

it would properly dispose connection pool

What is the value of this when the program is exiting?

[jtlisi]

If the Stop function in the cache interface is never called and there are currently no consequences, that sounds s like a good reason to remove the Stop function from the interface.