The current implementation starts/stops watcher using an executor. This
can result in our of order operations.
This commit reduces those executor calls to an absolute minimum in order
to be able to do state changes within the cluster state listener method,
which runs in sequence.
When a state change occurs that forces the watcher service to pause
(like no watcher index, no master node, no local shards), the service is
now in a paused state.
Pausing is a super lightweight operation, which marks the
ExecutionService as paused and waits for the currently executing watches
to finish in the background via an executor. The same applies for
stopping, the potentially long running operation is outsourced in to an
executor, as waiting for executed watches is decoupled from the current
state.
The only other long running operation is starting, where watches need to
be loaded. This is also done via an executor, but has an additional
protection by checking the cluster state version it was started with. If
another cluster state version was trying to load the watches, then this
loading will not take effect.
This PR also cleans up some unused states, like the a simple boolean in
the HistoryStore/TriggeredWatchStore marking it as started or stopped,
as this can now be caught in the execution service.
Another advantage of this approach is the fact, that now only triggered
watches are not getting executed, while watches that are run via the
Execute Watch API will still be executed regardless if watcher is
stopped or not.
Lastly the TickerScheduleTriggerEngine thread now only starts on data nodes.
In order to have less qa/ projects, this commit removes the
watcher-smoke-test-mustache and the watcher-smoke-test-painless projects
and moves the tests of both into the watcher-smoke-test projects.
This results in less projects to parse when calling gradle and a shorter test
time due to being able to run everything within one elasticsearch
instance.
This commit makes x-pack a module and adds it to the default
distrubtion. It also creates distributions for zip, tar, deb and rpm
which contain only oss code.
Alexander Reelsen
Ryan Ernst