[jira] [Assigned] (STRATOS-1439) Detecting Issues with Read Write Locks

["Mariangela Hills (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/STRATOS-1439?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

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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