Chetan Mehrotra created OAK-4483:
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Summary: Remove synchronized access requirement from
MetricStatisticsProvider#getStats
Key: OAK-4483
URL: https://issues.apache.org/jira/browse/OAK-4483
Project: Jackrabbit Oak
Issue Type: Improvement
Components: core
Affects Versions: 1.4
Reporter: Chetan Mehrotra
Assignee: Chetan Mehrotra
Fix For: 1.6, 1.4.4
{{MetricStatisticsProvider}} makes {{getStats}} as synchronized. This can cause
contention in concurrent scenarios specially when lots of Sessions are created
as the stats instance are looked at time of session creation
{noformat}
"qtp618865225-3444" #3444 prio=5 os_prio=0 tid=0x00007f7fe5083800 nid=0x7629
waiting for monitor entry [0x00007f7fdb9f7000]
java.lang.Thread.State: BLOCKED (on object monitor)
at
org.apache.jackrabbit.oak.plugins.metric.MetricStatisticsProvider.getStats(MetricStatisticsProvider.java:129)
- waiting to lock <0x00000003c1bfb1d0> (a
org.apache.jackrabbit.oak.plugins.metric.MetricStatisticsProvider)
at
org.apache.jackrabbit.oak.plugins.metric.MetricStatisticsProvider.getCounterStats(MetricStatisticsProvider.java:107)
at
org.apache.jackrabbit.oak.stats.StatisticManager.getStatsCounter(StatisticManager.java:99)
at
org.apache.jackrabbit.oak.jcr.session.SessionStats.<init>(SessionStats.java:83)
at
org.apache.jackrabbit.oak.jcr.delegate.SessionDelegate.<init>(SessionDelegate.java:150)
at
org.apache.jackrabbit.oak.jcr.repository.RepositoryImpl$1.<init>(RepositoryImpl.java:301)
at
org.apache.jackrabbit.oak.jcr.repository.RepositoryImpl.createSessionDelegate(RepositoryImpl.java:299)
at
org.apache.jackrabbit.oak.jcr.repository.RepositoryImpl.login(RepositoryImpl.java:281)
at
com.adobe.granite.repository.impl.CRX3RepositoryImpl.login(CRX3RepositoryImpl.java:94)
{noformat}
Instead of current approach it should use ConcurrentHashMap and still ensure
that duplicate metric instance did not get created
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