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https://issues.apache.org/jira/browse/SYNAPSE-659?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12876971#action_12876971
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Hiranya Jayathilaka commented on SYNAPSE-659:
---------------------------------------------
In order to fix this, I'm going to synchronize the register and unregister
methods in the registrar. Since the registrar is maintained as a singleton, it
will ensure only one thread can invoke these methods at a time. Also since
these methods are called only during the system initialization and shutdown,
synchronizing them does not have an impact on the runtime performance.
> MBeanRegistrar Is Not Thread Safe
> ---------------------------------
>
> Key: SYNAPSE-659
> URL: https://issues.apache.org/jira/browse/SYNAPSE-659
> Project: Synapse
> Issue Type: Bug
> Affects Versions: 1.2
> Reporter: Hiranya Jayathilaka
> Assignee: Hiranya Jayathilaka
> Fix For: 2.0
>
>
> The MBeanRegistrar implementation used to register various MBeans, is not
> thread safe. The register method can be invoked by multiple threads at the
> same time with the same arguments.With a sufficient level of contention, the
> registrar may attempt to register the same MBean multiple times. This results
> in an exception like this:
> [2010-06-09 11:28:56,840] WARN - MBeanRegistrar Error registering a MBean
> with name ' StatisticsView ' and category name ' StatisticsView' for JMX
> management
> javax.management.InstanceAlreadyExistsException:
> org.apache.synapse:Type=StatisticsView,Name=StatisticsView
> at com.sun.jmx.mbeanserver.Repository.addMBean(Repository.java:453)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.internal_addObject(DefaultMBeanServerInterceptor.java:1484)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerDynamicMBean(DefaultMBeanServerInterceptor.java:963)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerObject(DefaultMBeanServerInterceptor.java:917)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerMBean(DefaultMBeanServerInterceptor.java:312)
> at
> com.sun.jmx.mbeanserver.JmxMBeanServer.registerMBean(JmxMBeanServer.java:482)
> at
> org.apache.synapse.commons.jmx.MBeanRegistrar.registerMBean(MBeanRegistrar.java:51)
> at
> org.apache.synapse.aspects.statistics.StatisticsCollector.<init>(StatisticsCollector.java:36)
> at
> org.apache.synapse.aspects.statistics.StatisticsReporter.collectStatistics(StatisticsReporter.java:192)
> at
> org.apache.synapse.aspects.statistics.StatisticsReporter.reportForComponent(StatisticsReporter.java:56)
> at
> org.apache.synapse.core.axis2.ProxyServiceMessageReceiver.receive(ProxyServiceMessageReceiver.java:75)
> at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:178)
> at
> org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:167)
> at
> org.apache.synapse.transport.nhttp.ServerWorker.processEntityEnclosingMethod(ServerWorker.java:349)
> at
> org.apache.synapse.transport.nhttp.ServerWorker.run(ServerWorker.java:239)
> at
> org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:58)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:619)
> [2010-06-09 11:28:56,840] WARN - MBeanRegistrar Error registering a MBean
> with name ' StatisticsView ' and category name ' StatisticsView' for JMX
> management
> javax.management.InstanceAlreadyExistsException:
> org.apache.synapse:Type=StatisticsView,Name=StatisticsView
> at com.sun.jmx.mbeanserver.Repository.addMBean(Repository.java:453)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.internal_addObject(DefaultMBeanServerInterceptor.java:1484)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerDynamicMBean(DefaultMBeanServerInterceptor.java:963)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerObject(DefaultMBeanServerInterceptor.java:917)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerMBean(DefaultMBeanServerInterceptor.java:312)
> at
> com.sun.jmx.mbeanserver.JmxMBeanServer.registerMBean(JmxMBeanServer.java:482)
> at
> org.apache.synapse.commons.jmx.MBeanRegistrar.registerMBean(MBeanRegistrar.java:51)
> at
> org.apache.synapse.aspects.statistics.StatisticsCollector.<init>(StatisticsCollector.java:36)
> at
> org.apache.synapse.aspects.statistics.StatisticsReporter.collectStatistics(StatisticsReporter.java:192)
> at
> org.apache.synapse.aspects.statistics.StatisticsReporter.reportForComponent(StatisticsReporter.java:56)
> at
> org.apache.synapse.core.axis2.ProxyServiceMessageReceiver.receive(ProxyServiceMessageReceiver.java:75)
> at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:178)
> at
> org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:167)
> at
> org.apache.synapse.transport.nhttp.ServerWorker.processEntityEnclosingMethod(ServerWorker.java:349)
> at
> org.apache.synapse.transport.nhttp.ServerWorker.run(ServerWorker.java:239)
> at
> org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:58)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:619)
> [2010-06-09 11:28:56,840] WARN - MBeanRegistrar Error registering a MBean
> with name ' StatisticsView ' and category name ' StatisticsView' for JMX
> management
> javax.management.InstanceAlreadyExistsException:
> org.apache.synapse:Type=StatisticsView,Name=StatisticsView
> at com.sun.jmx.mbeanserver.Repository.addMBean(Repository.java:453)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.internal_addObject(DefaultMBeanServerInterceptor.java:1484)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerDynamicMBean(DefaultMBeanServerInterceptor.java:963)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerObject(DefaultMBeanServerInterceptor.java:917)
> at
> com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerMBean(DefaultMBeanServerInterceptor.java:312)
> at
> com.sun.jmx.mbeanserver.JmxMBeanServer.registerMBean(JmxMBeanServer.java:482)
> at
> org.apache.synapse.commons.jmx.MBeanRegistrar.registerMBean(MBeanRegistrar.java:51)
> at
> org.apache.synapse.aspects.statistics.StatisticsCollector.<init>(StatisticsCollector.java:36)
> at
> org.apache.synapse.aspects.statistics.StatisticsReporter.collectStatistics(StatisticsReporter.java:192)
> at
> org.apache.synapse.aspects.statistics.StatisticsReporter.reportForComponent(StatisticsReporter.java:56)
> at
> org.apache.synapse.core.axis2.ProxyServiceMessageReceiver.receive(ProxyServiceMessageReceiver.java:75)
> at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:178)
> at
> org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:167)
> at
> org.apache.synapse.transport.nhttp.ServerWorker.processEntityEnclosingMethod(ServerWorker.java:349)
> at
> org.apache.synapse.transport.nhttp.ServerWorker.run(ServerWorker.java:239)
> at
> org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:58)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:619)
> [2010-06-09 11:28:56,840] WARN - MBeanRegistrar Error registering a MBean
> with name ' StatisticsView ' and category name ' StatisticsView' for JMX
> management
> In this case I engaged statistics on an endpoint and then loaded the ESB with
> Java bench using 30 concurrent threads.
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