[jboss-jira] [JBoss JIRA] Created: (JBAS-5364) UnifiedInvokerHAProxy can throw NullPointerException under load
UnifiedInvokerHAProxy can throw NullPointerException under load
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Key: JBAS-5364
URL: http://jira.jboss.com/jira/browse/JBAS-5364
Project: JBoss Application Server
Issue Type: Bug
Security Level: Public (Everyone can see)
Components: Clustering
Affects Versions: JBossAS-5.0.0.Beta4, JBossAS-4.2.2.GA
Reporter: Galder Zamarreno
Assigned To: Galder Zamarreno
Under heavy load and sharing an EJB proxy between different threads, there's a
chance of NullPointerException like the one below being reported, specially when
using proxies configured with RoundRobin as load balance policy, such as SLSBs
or EJB2 home proxies:
java.lang.NullPointerException
at
org.jboss.invocation.unified.interfaces.UnifiedInvokerHAProxy.invoke(UnifiedInvokerHAProxy.java:186)
at org.jboss.invocation.InvokerInterceptor.invokeInvoker(InvokerInterceptor.java:365)
at
org.jboss.invocation.MarshallingInvokerInterceptor.invoke(MarshallingInvokerInterceptor.java:63)
at org.jboss.proxy.ejb.RetryInterceptor.invoke(RetryInterceptor.java:176)
at org.jboss.proxy.TransactionInterceptor.invoke(TransactionInterceptor.java:61)
at org.jboss.proxy.SecurityInterceptor.invoke(SecurityInterceptor.java:70)
at org.jboss.proxy.ejb.HomeInterceptor.invoke(HomeInterceptor.java:184)
at org.jboss.proxy.ClientContainer.invoke(ClientContainer.java:100)
at $Proxy1.create(Unknown Source)
Whenever a new target for an invocation is chosen, init(InvokerLocator locator)
method in UnifiedInvokerProxy is executed:
protected void init(InvokerLocator locator)
{
this.locator = locator;
try
{
client = createClient(locator, getSubSystem());
client.connect();
}
catch(Exception e)
{
log.fatal("Could not initialize UnifiedInvokerProxy.", e);
}
}
This method could be executed in paralell to the following in
UnifiedInvokerHAProxy.invoke(Invocation invocation):
Client clientInstance = getClient(invocation);
log.debug("Making invocation on " + clientInstance.getInvoker().getLocator());
When the new client instance is created, the invoker is null until client.connect() is
called, so something like this can happen:
1.- T1 (Thread 1) executes getClient(invocation); and returns client#1
2.- T2 (Thread 2) selects a new target for the invocation and calls init(InvokerLocator
locator)
3.- T2 calls createClient() and the instance variable client becomes client#2
4.- T1 now calls clientInstance.getInvoker().getLocator() which is now client#2 but
connect() has not been called on this instance, so results on NPE.
The simplest of all solutions would be to make assignment of client instance thread safe,
something I already did for JBAS-4815 to get around another thread safety issue.
I'm gonna take the tests I created for JBAS-4815 and use them to replicate something
like
this and check whether the fix for that fixes this as well.
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