"
Messaging service checks dc/rack of the target node when creating a
socket. However, this information is not available for all verbs, in
particular gossiper uses RPC to get topology from other nodes.
This generates a chicken-and-egg problem -- to create a socket messaging
service needs topology information, but in order to get one gossiper
needs to create a socket.
Other than gossiper, raft starts sending its APPEND_ENTRY messages early
enough so that topology info is not avaiable either.
The situation is extra-complicated with the fact that sockets are not
created for individual verbs. Instead, verbs are groupped into several
"indices" and socket is created for it. Thus, the "gossiping" index that
includes non-gossiper verbs will create topology-less socket for all
verbs in it. Worse -- raft sends messages w/o solicited topology, the
corresponding socket is created with the assumption that the peer lives
in default dc and rack which doesn't matchthe local nodes' dc/rack and
the whole index group gets the "randomly" configured socket.
Also, the tcp-nodelay tries to implement similar check, but uses wrong
index of 1, so it's also fixed here.
"
* 'br-messaging-topology-ignoring-clients' of https://github.com/xemul/scylla:
messaging_service: Fix gossiper verb group
messaging_service: Mind the absence of topology data when creating sockets
messaging_service: Templatize and rename remove_rpc_client_one
13ace7a05e