There is a flaw in how the raft rpc endpoints are
currently managed. The io_fiber in raft::server
is supposed to first add new servers to rpc, then
send all the messages and then remove the servers
which have been excluded from the configuration.
The problem is that the send_messages function
isn't synchronous, it schedules send_append_entries
to run after all the current requests to the
target server, which can happen
after we have already removed the server from address_map.
In this patch the remove_server function is changed to mark
the server_id as expiring rather than synchronously dropping it.
This means all currently scheduled requests to
that server will still be able to resolve
the ip address for that server_id.
Fixes: #11228Closes#11748
0923cb435f