Moves all remaining (rolling-upgrade and mixed-version) REST tests to use Zen2. To avoid adding
extra configuration, it relies on Zen2 being set as the default discovery type. This required a few
smaller changes in other tests. I've removed AzureMinimumMasterNodesTests which tests Zen1
functionality and dates from a time where host providers were not configurable and each cloud
plugin had its own discovery.type, subclassing the ZenDiscovery class. I've also adapted a few tests
which were unnecessarily adding addTestZenDiscovery = false for the same legacy reasons. Finally,
this also moves the unconfigured-node-name REST test to Zen2, testing the auto-bootstrapping
functionality in development mode when no discovery configuration is provided.
In real deployments it is important that clusters are properly configured to
avoid accidentally forming multiple independent clusters at cluster
bootstrapping time. However we also expect to be able to unpack Elasticsearch
and start up one or more nodes without any up-front configuration, and have
them do their best to find each other and form a cluster after a few seconds.
This change adds a delayed automatic bootstrapping process to nodes that start
up with no relevant settings set to support the desired out-of-the-box
experience without compromising safety in properly-configured deployments.
Change the logging infrastructure to handle when the node name isn't
available in `elasticsearch.yml`. In that case the node name is not
available until long after logging is configured. The biggest change is
that the node name logging no longer fixed at pattern build time.
Instead it is read from a `SetOnce` on every print. If it is unset it is
printed as `unknown` so we have something that fits in the pattern.
On normal startup we don't log anything until the node name is available
so we never see the `unknown`s.
Yannick Welsch
David Turner
Armin Braun
Nik Everett