Refer to #1598 (comment). It looks like @adleong's commit 9deb5f7 revealed a memory leak in long-running gRPC streams. This leak was probably already there, but wasn't being reached because the flow-control issue fixed in 9deb5f7 was preventing us from reaching a state in which it could occur.

@klingerf did some investigation of a heap dump (see #1598 (comment)) and it looks like unbounded AsyncQueue creation might be the cause of this leak. I talked it over w/ Alex & we suspect that long streams probably cause a future chain that gets longer and longer, probably in StreamProxy or BufferedStream.