Comment 1 for bug 1803629

Just to mention the Panic() that we saw is what happens if you have a shared mgo.Session and one side calls .Close() while the other side tries to do a query. (Using a closed Session is a panic())

" unable to return unknown model 308db235-38d6-4f31-8e4b-4cb5380900bf to the pool"

That sounds like we have a reference counting issue. Where something is grabbing access to a State object, and calls Release() on it, and a second bit of code is *also* calling Release on it.

That might be related to the Close() issue. If we ended up with 2 code paths getting a copy of the same State object, and then double releasing it, probably the first Release is triggering a cleanup, including closing the mgo session of that State object, and then the *second* Release is trying to use/close one that is already closed and thus you get the error and a panic.