CODEWITHSUNDEEP
ibm-mq
Yash
Yash

Reputation: 1018

Testing transaction capability of applications

Application 1(A1) sends messages to A2 over MQ. A2 uses XA transactions so that a message dropped on the queue is picked by A2, processed and written to the DB and the whole transaction is committed at once.

I would like to test whether A2 correctly maintains system consistency if the transaction fails mid-way and whether XA has been implemented correctly.

I would like to stop the DB as soon as A2 picks up the message. But I am not sure whether I will have enough time to stop the DB and whether I will know for sure that the message has been picked.

Any other suggestions for testing this?

Thanks,

Yash

Upvotes: 0

Views: 43

Answers (1)

Nicholas
Nicholas

Reputation: 16066

I am assuming you are using Java here, otherwise, some of this won't be applicable.

The quick, pragmatic solution is to inject a delay into your process which will give you time to take your transactionally destructive action. The easiest way to do this would be to run the app in a debugger. Place a breakpoint at some suitable location (perhaps after the message has been received and the DB write is complete but not committed) and kill the DB when the debugger pauses the thread. Alternatively, add a test hook to your code whereby the thread will sleep if the MQ message has a header titled something unlikely like 'sleeponmessagereceived'.

A more complex but sophisticated technique is to use error injection via some AOP tool. I would definitely look at Byteman. It allows you to inject bytecode at runtime and was originally written to test XA scenarios like yours for the Arjuna transaction manager. You can inject code procedurally, or you can annotate unit testing procedures. Some of the advantages of this approach is that you can direct Byteman to trigger an error condition based on a variety of other conditions, such as nth invocation, or if a method arg is X. Also, depending on how detailed your knowledge of your transaction manager is, you can recreate a wider set of scenarios to produce some more tricky XA outcomes like Heuristic exceptions. There's some examples here that demonstrate how to use Byteman scripts to validate MQ XA Recovery. This project is intended to help reproducing XA failure and recovery. It is JBoss specific, but I would imagine you would be able to adapt to your environment.

Upvotes: 1

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