Today we use `cluster.join.timeout` to prevent nodes from waiting indefinitely
if joining a faulty master that is too slow to respond, and
`cluster.publish.timeout` to allow a faulty master to detect that it is unable
to publish its cluster state updates in a timely fashion. If these timeouts
occur then the node restarts the discovery process in an attempt to find a
healthier master.
In the special case of `discovery.type: single-node` there is no point in
looking for another healthier master since the single node in the cluster is
all we've got. This commit suppresses these timeouts and instead lets the node
wait for joins and publications to succeed no matter how long this might take.
Today the lag detector may remove nodes from the cluster if they fail to apply
a cluster state within a reasonable timeframe, but it is rather unclear from
the default logging that this has occurred and there is very little extra
information beyond the fact that the removed node was lagging. Moreover the
only forewarning that the lag detector might be invoked is a message indicating
that cluster state publication took unreasonably long, which does not contain
enough information to investigate the problem further.
This commit adds a good deal more detail to make the issues of slow nodes more
prominent:
- after 10 seconds (by default) we log an INFO message indicating that a
publication is still waiting for responses from some nodes, including the
identities of the problematic nodes.
- when the publication times out after 30 seconds (by default) we log a WARN
message identifying the nodes that are still pending.
- the lag detector logs a more detailed warning when a fatally-lagging node is
detected.
- if applying a cluster state takes too long then the cluster applier service
logs a breakdown of all the tasks it ran as part of that process.
In #38333 and #38350 we moved away from the `discovery.zen` settings namespace
since these settings have an effect even though Zen Discovery itself is being
phased out. This change aligns the documentation and the names of related
classes and methods with the newly-introduced naming conventions.
Renames the following settings to remove the mention of `zen` in their names:
- `discovery.zen.hosts_provider` -> `discovery.seed_providers`
- `discovery.zen.ping.unicast.concurrent_connects` -> `discovery.seed_resolver.max_concurrent_resolvers`
- `discovery.zen.ping.unicast.hosts.resolve_timeout` -> `discovery.seed_resolver.timeout`
- `discovery.zen.ping.unicast.hosts` -> `discovery.seed_addresses`
Reduces the leader and follower check timeout to 3 * 10 = 30s instead of 3 * 30 = 90s, with 30s still
being a very long time for a node to be completely unresponsive.
David Turner
Lisa Cawley
Yannick Welsch