Friday, May 23, 2008

Custom Decision Service

I am not very big fan of Decision Service which comes out of the box with Oracle BPEL. There are couple of issues I found

- It creates whole bunch JAXB classes in my bpel process, which are .java and .class files (I have to keep both of them, .class files are not generated during compilation of bpel process!)

- I can NOT change the created Decision Service, it is not like I can click on DB adapter and reconfigure it. It make my life extremely difficult when have to accommodate changes from client

- I can not call the service from ESB or other WS consumer, the decision service exposed takes millions of parameters which are not relevant to web service consumer (e.g. bpelInstanceId? why in the hell rule engine needs to know bpel instance id?)

- There is a decision service for each partner link! We have 20 BPEL processes making almost 30 different type of calls, that ends up in 30 decision services. That make my life impossible to manage.

- It is way too complicated to implement WSIF with the decision service.

I love the idea of BAM, where all Active Data cache operations are exposed as one service. I had very naive and romantic idea of implementing my custom decision service and talk to any type of rule set, rule function, do the connection pooling of rules via one web service interface. It can take any type of parameter and using Java reflection I can convert to right type and that's all I need. My client did buy this idea and I implemented very nice and generic Custom Decision Service.

1. Implemented POJO

- I implemented a small Java POJO service, which does takes configuration

e.g. RuleRepositoryType (webdav, files), File Repository Connection Information, WebDav Repository Connection Information, Whole bunch of debug flags which are supported by Rule Engine, Dictionary Name, Rule Function or Rule Set, Input types and output types.

2. Implemented EJB 3.0 and exposed as Web service via annotations

- Just created EJB 3.0 session facade on top of POJO so that it is container managed, I can easily expose as Web Service via Annotations, and for implementing Connection pool.

3. Implemented Connection Pooling in EJB

- I implemented custom connection pool of Rule Repository and Rule Dictionary. I initiate new Rule Session each time. I also noticed that pooling/caching Rule repository was not just good enough so I had to cache Rule Dictionary as well. Yeah, I implemented

4. WSIF Interface via annotations

- I just followed to create WSIF on top of my EJB 3.0 session facade.

5. Performance Matrix

Test case: Used WebDav repository, Rule Function interface which executes more than 10 rule sets and creates whole bunch of external connection. It usually takes about 2 seconds to complete the Rule Session itself. I used about 10 threads and loop of 50 with 1 second delay in each (so total number of instances will be 500).

Default Decision Service over SOAP: I created sample BPEL process and created decision service with decide activity (which comes with jaxb java and classes, jar, ear, war, and so on...). Here were the results:

Average execution time: 3.1 second

Number of failures: 15

Custom Decision Service over SOAP: To be fair I didn't use WSIF interface. Calling my custom decision service over soap protocol. It is just like normal partner link.

Average execution time: 3.5 second

Number of failures: 10


- Reason behind slowness is because of I am doing more reflection which is a bit expensive.

- Because of EJB and container managed stuff, I am getting less number of failures.

- Out-of-box decision service caches the Rule Connection where the custom decision service manages the entire pool which is shared across the enterprise. I believe if I test with 20 different BPEL processes with different pattern of calls, I will be far ahead in comparison with default decision service.

I am more than willing to get your feedback on this. I am not sure if I did right thing, but I believe I reduced (rather completely eliminated) overhead for managing far complex default decision service.

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