mirror of
https://github.com/scylladb/scylladb.git
synced 2026-05-31 20:16:43 +00:00
73e5298273
1) make address map API flexible Before this patch: - having a mapping without an actual IP address was an internal error - not having a mapping for an IP address was an internal error - re-mapping to a new IP address wasn't allowed After this patch: - the address map may contain a mapping without an actual IP address, and the caller must be prepared for it: find() will return a nullopt. This happens when we first add an entry to Raft configuration and only later learn its IP address, e.g. via gossip. - it is allowed to re-map an existing entry to a new address; 2) subscribe to gossip notifications Learning IP addresses from gossip allows us to adjust the address map whenever a node IP address changes. Gossiper is also the only valid source of re-mapping, other sources (RPC) should not re-map, since otherwise a packet from a removed server can remap the id to a wrong address and impact liveness of a Raft cluster. 3) prompt address map state with app state Initialize the raft address map with initial gossip application state, specifically IPs of members of the cluster. With this, we no longer need to store these IPs in Raft configuration (and update them when they change). The obvious drawback of this approach is that a node may join Raft config before it propagates its IP address to the cluster via gossip - so the boot process has to wait until it happens. Gossip also doesn't tell us which IPs are members of Raft configuration, so we subscribe to Group0 configuration changes to mark the members of Raft config "non-expiring" in the address translation map. Thanks to the changes above, Raft configuration no longer stores IP addresses. We still keep the 'server_info' column in the raft_config system table, in case we change our mind or decide to store something else in there.