Stefan Egli created SLING-5284:
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Summary: use dedicate thread instead of scheduler
Key: SLING-5284
URL: https://issues.apache.org/jira/browse/SLING-5284
Project: Sling
Issue Type: Improvement
Components: Extensions
Affects Versions: Discovery Base 1.0.2, Discovery Oak 1.0.2, Discovery Impl
1.2.0
Reporter: Stefan Egli
Assignee: Stefan Egli
Fix For: Discovery Impl 1.2.2, Discovery Base 1.0.4, Discovery Oak
1.0.4
Currently discovery (base/oak/impl) use the sling scheduler for scheduling the
background jobs that periodically issue heartbeats, ping the topology
connectors and check if the view is current. It's very important that these
jobs run at the exact defined periods - delays of a few minutes can break their
usefullness and in the end cause an instability in the topology. Sling
scheduler uses a thread-pool which is by definition limited. And if, for some
reason, this pool is busy doing other stuff, then the job is not executed for a
certain amount of time. Consider the situation when all the jobs are busy with
other things (non discovery stuff) when discovery wants to store a heartbeat or
monitor the view - that's then not possible and gets delayed. If the delay is
big enough to let the heartbeats time out (or changes to get unnoticed), then
the topology can break.
Thus to avoid this, instead of relying on the size-bound-scheduler, use a
dedicated thread for these high priority tasks.
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