Kenneth Howe created GEODE-5281:
-----------------------------------
Summary: Race between registering and unregistering CustomMXBeans
in concurrent thread may result in NPE
Key: GEODE-5281
URL: https://issues.apache.org/jira/browse/GEODE-5281
Project: Geode
Issue Type: Improvement
Components: jmx
Reporter: Kenneth Howe
Stack trace from an example of the unexpected NullPointerException in
{{MBeanProxyFactory.createProxy()}}
{code:java}
[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)
{code}
The registering thread enters
{code}
public void createProxy(DistributedMember member, ObjectName objectName,
Region<String, Object> monitoringRegion, Object newVal) {
{code}
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.
{code}
String name = objectName.toString();
FederationComponent federationComponent = (FederationComponent)
monitoringRegion.get(name);
String interfaceClassName = federationComponent.getMBeanInterfaceClass();
{code}
{{federationComponent == null}} results in the NPE.
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