[jboss-jira] [JBoss JIRA] Commented: (JBAS-5364) UnifiedInvokerHAProxy can throw NullPointerException under load

UnifiedInvokerHAProxy can throw NullPointerException under load --------------------------------------------------------------- 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.