This change cleans up "unused variable" warnings. There are several cases were we
most likely want to suppress the warnings (especially in the client documentation test
where the snippets contain many unused variables). In a lot of cases the unused
variables can just be deleted though.
* INGEST: Fix ThreadWatchDog Throwing on Shutdown
* #32539 is caused by the fact that ThreadWatchDog.Default could throw on shutdown if the ThreadPool is interrupted while `interruptLongRunningExecutions` is in progress. This is a result of the watchdog not having a lifecycle of its own (normally it terminates when the threadpool terminates).
* We can't easily use `org.elasticsearch.common.util.concurrent.EsRejectedExecutionException#isExecutorShutdown` to catch this state the same way other components do since thatwould require adding the core lib to Grok as a dependency
* Since we have no knowledge of the lifecycle in this compontent since we're only passed the scheduler `BiFunction` I fixed this by only scheduling the watchdog when there's actually registered threads in it.
* I think using the patter of locking via two `Atomic*` values should not be much of a performance concern here under load since either the integer will likely be > 0 in this case (because we have multiple Grok in parallel) or the running state will be true because there likely was at least one thread registered when the watchdog ran and so the enqueing of the watchdog task during `register` will happen very rarely here (in the worst case scenario of only a single Grok thread it will happen less frequently than once every `ingest.grok.watchdog.interval`). The atomic update on the count should not be relevant relative to the cost of adding a new node to the CHM either.
* Fixes#32539
* Also fixes the watchdog to run if it doens't have to in general.
This adds a thread interrupter that allows us to encapsulate calls to org.joni.Matcher#search()
This method can hang forever if the regex expression is too complex.
The thread interrupter in the background checks every 3 seconds whether there are threads
execution the org.joni.Matcher#search() method for longer than 5 seconds and
if so interrupts these threads.
Joni has checks that that for every 30k iterations it checks if the current thread is interrupted and
if so returns org.joni.Matcher#INTERRUPTED
Closes#28731
John
Christoph Büscher
Armin Braun
Martijn van Groningen
Tanguy Leroux