Getting this error in my logstash-plain.log. There doesn't seem to be an exact frequency from what I can tell - or exact replication steps. It is not affecting messages going the output filters. This logstash is installed from logstash-5.0.0-beta1.rpm. Interestingly, the error seems to not occur when I change the log level from default/info to debug. Possible metric API issue? Or maybe something that just needs some more precise error handling to better identify the issue? Unless of course I am missing something obvious.
[2016-10-06T22:59:02,450][ERROR][logstash.instrument.periodicpoller.jvm] PeriodicPoller: exception {:poller=>#<LogStash::Instrument::PeriodicPoller::JVM:0x1724e9f5 @task=#<Concurrent::TimerTask:0x554897af @observers=#<Concurrent::Collection::CopyOnNotifyObserverSet:0x3e394ed0 @observers={#<LogStash::Instrument::PeriodicPoller::JVM:0x1724e9f5 ...>=>:update}>, @timeout_interval=60.0, @running=#<Concurrent::AtomicBoolean:0x5fa80d2a>, @StoppedEvent=#<Concurrent::Event:0x4e4c1c9f @set=false, @iteration=0>, @execution_interval=1.0, @do_nothing_on_deref=true, @run_now=nil, @freeze_on_deref=nil, @executor=#<Concurrent::SafeTaskExecutor:0x3a779448 @task=#<Proc:0x19547770@/usr/share/logstash/logstash-core/lib/logstash/instrument/periodic_poller/base.rb:52>, @exception_class=StandardError>, @StopEvent=#<Concurrent::Event:0x68af82d @set=false, @iteration=0>, @value=nil, @copy_on_deref=nil, @dup_on_deref=nil>, @peak_threads=36, @peak_open_fds=260, @metric=#<LogStash::Instrument::Metric:0x280ca487 @collector=#<LogStash::Instrument::Collector:0x4e5cd56 @agent=nil, @metric_store=#<LogStash::Instrument::MetricStore:0x2e5fb01a @store=#<Concurrent::Map:0x148aad56 @default_proc=nil>, @structured_lookup_mutex=#<Mutex:0x4510747a>, @fast_lookup=#<Concurrent::Map:0x8f5d8c3 @default_proc=nil>>, @observer_state=false, @snapshot_task=#<Concurrent::TimerTask:0x5bf966a7 @observers=#<Concurrent::Collection::CopyOnNotifyObserverSet:0x1a588093 @observers={#<LogStash::Instrument::Collector:0x4e5cd56 ...>=>:update}>, @timeout_interval=600.0, @running=#<Concurrent::AtomicBoolean:0x7a386c90>, @StoppedEvent=#<Concurrent::Event:0x6ae4f12e @set=false, @iteration=0>, @execution_interval=1.0, @do_nothing_on_deref=true, @run_now=nil, @freeze_on_deref=nil, @executor=#<Concurrent::SafeTaskExecutor:0x34e6b8f9 @task=#<Proc:0x4db87d7@/usr/share/logstash/logstash-core/lib/logstash/instrument/collector.rb:87>, @exception_class=StandardError>, @StopEvent=#<Concurrent::Event:0x3d3e2730 @set=false, @iteration=0>, @value=false, @copy_on_deref=nil, @dup_on_deref=nil>>>, @options={:polling_interval=>1, :polling_timeout=>60}>, :result=>nil, :exception=>#<Concurrent::TimeoutError: Concurrent::TimeoutError>, :executed_at=>2016-10-06 22:59:02 -0400}