dinsdag 25 juni 2013

Oracle SOA 11g BPEL transaction semantics and performance

In this post I'll provide a simple integration example and provide some suggestions to optimize the performance. Optimization suggestions are focused on transaction semantics. It's purpose is to indicate the importance to take into account various settings related to transaction management.

The base and inspiration for this post are the presentations and material from SOA Blackbelt training which was given by Oracle in Berlin this year from the 11th to the 14th of June. The training covered a lot of material in great depth. If you have the chance to follow it, I highly recommend it!

Test setup

First I enqueue 2000 messages on an Oracle AQ and take a timestamp which I write in a separate table in the same transaction. After a COMMIT, a BPEL process is triggered and picks up the messages (one instance per message). This process puts the message in a table. The moment of insertion is determined by having a default value on a field in the table. I then determine the time difference between the last message put in the table in the batch and the moment of insertion in the AQ. To avoid the overhead of audit logging, I turn this off for the specific process. The code used can be downloaded at the end of this post.

I will vary the bpel.config.oneWayDeliveryPolicy. I will try sync and async.persist (the default). async.persist will first put dequeued messages in the DLV_MESSAGE table before they are further processed in a separate transaction. sync will not do this and will invoke the BPEL process synchronously. I use three different datasource settings for this test. I will try both oneWayDeliveryPolicy settings with an XA datasource (which uses a 2-phase commit) and two non XA datasources. For the non XA datasource I will test with and without Global Transaction support. I will test this using different datasources and the same datasource. I will also test all combinations with the bpel.config.transaction setting to required and requiresNew.

Summarized; four different settings are varied in all combinations of the other settings. Two measures are taken with each combination.
- bpel.config.oneWayDeliveryPolicy (async.persist, sync)
- bpel.config.transaction (required, requiresNew)
- different datasource settings; XA, NonXA, NonXA no global transaction support
- using the same and different datasources with the same settings

I created 6 datasources with the three different settings;
testuserXa, testuserXa2
testuserNonXa, testuserNonXa2
testuserNonXaGlobal, testuserNonXaGlobal2

Next I created 6 connection factories for the DbAdapter and 6 connection factories for the AqAdapter. I varied the datasources in the JCA files in the BPEL process I created. For every test I primed the datasources/engine with 100 messages. Next I took 2 measures of 2000 messages.

Results


The * indicates the process failed with the following exception;
BINDING.JCA-11616
DBWriteInteractionSpec Execute Failed Exception.
insert failed. Descriptor name: [WriteToStore.TestStore].
Caused by java.sql.SQLException: Cannot call Connection.commit in distributed transaction.  Transaction Manager will commit the resource manager when the distributed transaction is committed..

As can be seen, using an XA datasource decreased performance. Also using the sync property increased performance. In this example, little effect was visible when changing the transaction property. There was little difference in using two different datasources instead of a single datasource for processing. The NonXa datasource with global transaction support executed an explicit commit (apparently) which conflicted with the distributed nature of the transaction. This happened in all cases when performing an insert action using this datasource. This also indicates the transaction was distributed in all cases (even when using a Non Xa datasource without global transaction support).

Conclusion

When using the oneWayDeliveryPolicy setting of sync, the entire process is processed in a single transaction. When using async.persist, 2 transactions are involved. One to write to the DLV_MESSAGE table and one to call the DB insert.

The performance impact of writing to DLV_MESSAGE and the extra transaction was measurable. When calling a process synchronously, the effect would have been greater since then it would have been 4 transactions when using the async.persist setting.

Using an XA datasource means a two-phase commit is used. This has a slight overhead which is measurable in this example. It also provides a difference in behavior, mainly in the event of a fault. See for example; http://soaranch.wordpress.com/2010/10/08/global-and-local-transactions-in-oracle-soa-11g-composites/.

Because of the process setup, I could not measure much effect on the transaction setting since the process initialization by the Aq adapter always starts a new transaction. When a process is called from another process, I would have expected to see a performance gain with the 'required' setting since then I woukld have expected less transactions.

I would have liked to see if the DbAdapter and AqAdapter behaved differently when different datasources on the same database schema were used to connect instead of the same datasource. The only difference found however was that when using async.persist, requiresNew and using the same NonXA datasource without global transaction support, errors occurred. These errors did not occur when using different datasources (also NonXA without global transaction support). Apparently with these settings, an explicit commit is executed when performing an insert by using the DbAdapter. Also the incoming message was read using the AqAdapter and the result was written using the DbAdapter. These adapters both have their own connectionpools. Using the same adapter might have caused different behavior. Using different datasources might make it possible to have more open incoming connections. This however in this case was most likely limited by other settings such as invoker threads.

Something to mind when considering the transaction related settings is it's impact on fault handling. This is however not the focus of this post. See for example; http://docs.oracle.com/cd/E15523_01/integration.1111/e10224/soa_transactions.htm and https://blogs.oracle.com/soabpm/entry/soa_suite_11g_-_transactions_b

Of course many other settings can be tuned to increase performance. The effects found when changing the settings might also differ with the nature of the process tested. In this case, invoker threads can be increased to allow messages to be picked up faster and the maximum number of connections allowed by the datasources can be increased. The process can also be made transient. The list of other possible options to make this specific process go faster are numerous. The purpose of this example is however to indicate the impact transactions can have on the performance of a process so the other factors are kept constant and the default settings from the Oracle SOA 11g PS5 image are used; http://www.oracle.com/technetwork/middleware/soasuite/learnmore/vmsoa-172279.html

You can download the used code and test results below;
https://dl.dropboxusercontent.com/u/6693935/blog/Transactions.zip