[GEODE-5281] Race between registering and unregistering CustomMXBeans in concurrent thread may result in NPE

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.0.0-incubating
• Fix Version/s: 1.7.0
• Component/s: jmx
• Labels: pull-request-available
• Assignee: Ken Howe
• Reporter: Ken Howe
• Created: 04/Jun/18 15:43
• Updated: 03/Oct/18 21:38
• Resolved: 06/Jul/18 15:08

Description

Stack trace from an example of the unexpected NullPointerException in MBeanProxyFactory.createProxy()

[warning 2018/02/03 17:32:13.561 UTC managing_1_gemfire2_79a23c4a-f5e3-4c9f-6455-149c397ce13c_38199 <pool-3-thread-4> tid=0x5e] Create Proxy failed for GemFire:type=CustomMXBean213,member=locator_managing_gemfire1_79a23c4a-f5e3-4c9f-6455-149c397ce13c_37116 with exception null
java.lang.NullPointerException
        at org.apache.geode.management.internal.MBeanProxyFactory.createProxy(MBeanProxyFactory.java:83)
        at org.apache.geode.management.internal.MBeanProxyFactory.createAllProxies(MBeanProxyFactory.java:137)
        at org.apache.geode.management.internal.FederatingManager$GIITask.call(FederatingManager.java:457)
        at org.apache.geode.management.internal.FederatingManager$GIITask.call(FederatingManager.java:341)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)

The registering thread enters

  public void createProxy(DistributedMember member, ObjectName objectName,
      Region<String, Object> monitoringRegion, Object newVal) {

with the objectName existing in the _monitoringRegion. A few lines further the entry is retrieved from the region, but is now null due to it being removed by the unregistering thread.

      String name = objectName.toString();
      FederationComponent federationComponent = (FederationComponent) monitoringRegion.get(name);
      String interfaceClassName = federationComponent.getMBeanInterfaceClass();

federationComponent == null results in the NPE.

Issue Links

• links to: GitHub Pull Request #2096