[jboss-jira] [JBoss JIRA] Created: (JBAS-7535) Handle nested transactions in transaction-sticky load balance policies

[Brian Stansberry (JIRA)]

Handle nested transactions in transaction-sticky load balance policies
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                 Key: JBAS-7535
                 URL: https://jira.jboss.org/jira/browse/JBAS-7535
             Project: JBoss Application Server
          Issue Type: Feature Request
      Security Level: Public (Everyone can see)
          Components: Clustering
            Reporter: Brian Stansberry
            Assignee: Brian Stansberry
             Fix For: JBossAS-6.0.0.CR1


If the client creates a nested transaction, ClientUserTransactionStickyInterceptor doesn't detect that the TransactionPropagationContext has changed following the response, and thus doesn't associate the target with the new TPC. Effect is the new TPC is not sticky.

One possibility is to throw NotSupportedTransaction if we detect a nested transaction. But from a quick look at this code, it seems easier to support nested transactions than to throw NotSupportedTransaction. Is it as simple as detecting if the TPC changes from before and after the invocation and storing the target if it has?

public class ClientUserTransactionStickyInterceptor extends AbstractTransactionStickyInterceptor
{
   @Override
   public Object invoke(Invocation invocation) throws Throwable
   {
      putIfExistsTransactionTarget(invocation);
      Object existingTPC = getTransactionPropagationContext(); // NEW
      Object response = getNext().invoke(invocation);
      invocationHasReachedAServer(invocation, response, existingTPC); //NEW
      return response;
   }

   public void invocationHasReachedAServer(Invocation invocation, Object response, Object existingTPC)
   {
      Object tpc = getTransactionPropagationContext();
      if (tpc == null || tpc.equals(existingTPC) == false) // NEW
      {
         /* If tpc is null when invoking a UserTransaction operation, begin()
          * is being called, so we remember the target where the transaction
          * was started.
          */
         rememberTransactionTarget(invocation, response);
      }
   }
} 

I don't much like detecting the nested transaction in advance and throwing an exception. Certainly not if we *can* support nested transactions; in that case it's not the interceptors place to decide what the server allows. AFAICT throwing an exception would require doing something ugly like this on every call

Object existingTPC = getTransactionPropagationContext();
if (existingTPC != null && ("begin".equals(invocation.getMethod().getName()) && invocation.getMethod().getDeclaringClass().equals(UserTransaction.class))
{
    throw new NotSupportedTransaction("blah blah blah");
}
putIfExistsTransactionTarget(invocation);
Object response = getNext().invoke(invocation);
invocationHasReachedAServer(invocation, response); 

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