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https://issues.apache.org/jira/browse/STRATOS-1439?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mariangela Hills reassigned STRATOS-1439:
-----------------------------------------
Assignee: Mariangela Hills
> Detecting Issues with Read Write Locks
> --------------------------------------
>
> Key: STRATOS-1439
> URL: https://issues.apache.org/jira/browse/STRATOS-1439
> Project: Stratos
> Issue Type: Task
> Components: Documentation
> Affects Versions: 4.1.0
> Reporter: Mariangela Hills
> Assignee: Mariangela Hills
> Fix For: 4.1.0
>
>
> Derive the information provided by Imesh in the email thread [1] and add it
> to the developer guide.
> [1] [Discuss] Detecting Issues with Read Write Locks
> ----------------------
> Hi Devs,
> Currently we have significant amount of read write locks in Stratos codebase
> to synchronize data structure updates made by multiple threads.
> As I figured out recently there are several possibilities that these locks
> could cause problems if not properly implemented:
> Problem 1: A thread trying to acquire a write lock while having a read lock.
> Problem 2: Locks acquired but not released
> I just implemented a ReadWriteLock class in stratos common module which could
> detect these problems. This class make use of
> java.util.concurrent.locks.ReentrantReadWriteLock and implements additional
> logic to detect problems. By default problem 2 detection logic is disabled,
> it can be enabled by setting following system property:
> read.write.lock.monitor.enabled=true
> I have now updated all read write locks with the above class.
> Following is an example scenario where I detected an unreleased lock in the
> REST API:
> org.apache.stratos.common.exception.LockNotReleasedException
> at
> org.apache.stratos.common.concurrent.locks.ReadWriteLockMonitor.checkTimeout(ReadWriteLockMonitor.java:71)
> at
> org.apache.stratos.common.concurrent.locks.ReadWriteLockMonitor.run(ReadWriteLockMonitor.java:50)
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
> at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:304)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run(Thread.java:745)
> [2015-01-20 18:30:12,952] ERROR
> {org.apache.stratos.common.concurrent.locks.ReadWriteLockMonitor} - System
> error, lock has not released for 30 seconds: [lock-name] topology [lock-type]
> Read [thread-id] 405 [thread-name] http-nio-9443-exec-21 [stack-trace]
> java.lang.Thread.getStackTrace(Thread.java:1589)
> org.apache.stratos.common.concurrent.locks.ReadWriteLock.acquireReadLock(ReadWriteLock.java:160)
> org.apache.stratos.messaging.message.receiver.topology.TopologyManager.acquireReadLockForCluster(TopologyManager.java:173)
> org.apache.stratos.rest.endpoint.api.StratosApiV41Utils.addClustersInstancesToGroupInstanceBean(StratosApiV41Utils.java:1015)
> org.apache.stratos.rest.endpoint.api.StratosApiV41Utils.setSubGroupInstances(StratosApiV41Utils.java:1027)
> org.apache.stratos.rest.endpoint.api.StratosApiV41Utils.addGroupsInstancesToApplicationInstanceBean(StratosApiV41Utils.java:979)
> org.apache.stratos.rest.endpoint.api.StratosApiV41Utils.getApplicationRuntime(StratosApiV41Utils.java:963)
> org.apache.stratos.rest.endpoint.api.StratosApiV41.getApplicationRuntime(StratosApiV41.java:579)
> Thanks
> Imesh
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