If a node is partitioned away from the rest of the cluster then the
`ClusterFormationFailureHelper` periodically reports that it cannot
discover the expected collection of nodes, but does not indicate why. To
prove it's a connectivity problem, users must today restart the node
with `DEBUG` logging on `org.elasticsearch.discovery.PeerFinder` to see
further details.
With this commit we log messages at `WARN` level if the node remains
disconnected for longer than a configurable timeout, which defaults to 5
minutes.
Relates #72968
Today the discovery phase has a short 1-second timeout for handshaking
with a remote node after connecting, which allows it to quickly move on
and retry in the case of connecting to something that doesn't respond
straight away (e.g. it isn't an Elasticsearch node).
This short timeout was necessary when the component was first developed
because each connection attempt would block a thread. Since #42636 the
connection attempt is now nonblocking so we can apply a more relaxed
timeout.
If transport security is enabled then our handshake timeout applies to
the TLS handshake followed by the Elasticsearch handshake. If the TLS
handshake alone takes over a second then the whole handshake times out
with a `ConnectTransportException`, but this does not tell us which of
the two individual handshakes took so long.
TLS handshakes have their own 10-second timeout, which if reached yields
a `SslHandshakeTimeoutException` that allows us to distinguish a problem
at the TLS level from one at the Elasticsearch level. Therefore this
commit extends the discovery probe timeouts.
Elasticsearch currently blocks writes by default when a master is unavailable. The cluster.no_master_block setting allows
a user to change this behavior to also block reads when a master is unavailable. This PR introduces a way to now also still
allow writes when a master is offline. Writes will continue to work as long as routing table changes are not needed (as
those require the master for consistency), or if dynamic mapping updates are not required (as again, these require the
master for consistency).
Eventually we should switch the default of cluster.no_master_block to this new mode.
There is no point in timing out a join attempt any more. Timing out and
retrying with the same master is pointless, and an in-flight join
attempt to one master no longer blocks attempts to join other masters.
This commit removes this unnecessary setting.
Relates #60872 in which this setting was deprecated.
* Moves `Discovery and cluster formation` content from `Modules` to
`Set up Elasticsearch`.
* Combines `Adding and removing nodes` with `Adding nodes to your
cluster`. Adds related redirect.
* Removes and redirects the `Modules` page.
* Rewrites parts of `Discovery and cluster formation` to remove `module`
references and meta references to the section.
The introductory sections of the reference manual contains some simplified
instructions for adding a node to the cluster. Unfortunately they are a little
too simplified and only really work for clusters running on `localhost`. If you
try and follow these instructions for a distributed cluster then the new node
will, confusingly, auto-bootstrap itself into a distinct one-node cluster.
Multiple nodes running on localhost is a valid config, of course, but we should
spell out that these instructions are really only for experimentation and that
it takes a bit more work to add nodes to a distributed cluster. This commit
does so.
Also, the "important config" instructions for discovery say that you MUST set
`discovery.seed_hosts` whereas in fact it is fine to ignore this setting and
use a dynamic discovery mechanism instead. This commit weakens this statement
and links to the docs for dynamic discovery mechanisms.
Finally, this section is also overloaded with some technical details that are
not important for this context and are adequately covered elsewhere, and
completely fails to note that the default discovery port is 9300. This commit
addresses this.
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.
Removes all traces of Zen1 from the code base. Some of these commits will also be backported to
7.0/7.x (#39470) as the cluster.coordination package was making use of some things in
discovery.zen and we want to keep 7.x as close as possible to master.
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
James Rodewig
Yannick Welsch
James Rodewig
Lisa Cawley