[jira] [Created] (OAK-3398) make lease update more robust

["Stefan Egli (JIRA)" <ji...@apache.org>]

Stefan Egli created OAK-3398:
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             Summary: make lease update more robust
                 Key: OAK-3398
                 URL: https://issues.apache.org/jira/browse/OAK-3398
             Project: Jackrabbit Oak
          Issue Type: Improvement
          Components: core
    Affects Versions: 1.3.6
            Reporter: Stefan Egli
            Assignee: Stefan Egli
             Fix For: 1.3.7


With the lease check introduced in OAK-2739 (and refined to do a oak-core stop in OAK-3397) it becomes more critical that the lease is always properly updated (to avoid an unnecessary oak-core stop). The following issues exist atm:
* currently the lease is valid 60sec by default, updated every 20sec, the lease check fails with a margin of 20sec *before* it times out. this means if the lease update thread is not operating for 20sec it will cause a stop. that's quite a low figure probably
** the suggestion is to increase the lease timeout to 120sec from 60sec - update it as soon as 10sec has been eaten off it, and leave the 20sec safety margin at the end. This would result in 90sec 'idle equals faulty'
* on a machine with heavy load it seems likely that the lease-update-thread doesn't get scheduled timely enough - as it races for cpu against all the other busy threads
** the suggestion is to increase the thread priority of the lease update thread - so if the VM supports thread priorities, that would help reduce lease failure 'just because the cpu is too busy'
* the ClusterNodeInfo, when renewing the lease, doesn't check if the lease has been marked as timed-out/recovering by another instance. it just overwrites whatever is there. 
** It should, however, only update the lease when it has not yet been marked as timed out.



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