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https://issues.apache.org/jira/browse/SYNAPSE-659?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12876976#action_12876976
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Hiranya Jayathilaka commented on SYNAPSE-659:
---------------------------------------------
Just had another look at the design and it seems the race condition can occur
only when registering the statistics MBean. All other MBeans (endpoints, server
management, datasources etc) are registered by single thread instances. So we
can just synchronize the invocation in the StatisticsCollector class.
> 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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