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From Dakshika Jayathilaka <daksh...@wso2.com>
Subject Re: [Discuss] Detecting Issues with Read Write Locks
Date Tue, 20 Jan 2015 16:56:23 GMT
Great Work imesh.. This will help to developers in many ways..

Better if we can add this to developer guide.

*Dakshika Jayathilaka*
Software Engineer
WSO2, Inc.
lean.enterprise.middleware
0771100911

On Tue, Jan 20, 2015 at 7:08 PM, Imesh Gunaratne <imesh@apache.org> wrote:

> Above issue is now fixed with commit revision:
> fe0e6f81a673d6db815a56a3592c41441c4be3ae
>
> On Tue, Jan 20, 2015 at 7:03 PM, Imesh Gunaratne <imesh@apache.org> wrote:
>
>> Following JIRA explains the above problem found in 4.1.0-alpha:
>> https://issues.apache.org/jira/browse/STRATOS-1089
>>
>> On Tue, Jan 20, 2015 at 6:50 PM, Imesh Gunaratne <imesh@apache.org>
>> wrote:
>>
>>> 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 Gunaratne
>>>
>>> Technical Lead, WSO2
>>> Committer & PMC Member, Apache Stratos
>>>
>>
>>
>>
>> --
>> Imesh Gunaratne
>>
>> Technical Lead, WSO2
>> Committer & PMC Member, Apache Stratos
>>
>
>
>
> --
> Imesh Gunaratne
>
> Technical Lead, WSO2
> Committer & PMC Member, Apache Stratos
>

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