AS11 SOA : Tracing events using event logger

If you are publishing events in AS11 and would like to trace it : A quick check to see whether event has been published or not would be using event logger.

http://:port/soa-infra/events/edn-db-log

Of course, you can also use Enterprise Manager (em) to trace the event. There are multiple ways to trace them in EM.

1. Through instance tracking on the subscribing composite,
2. Business Events page in EM ( Right click on soa-infra -> select Business Events)
3. Looking into log files ( once again via EM)

Event vs Services to initiate a BPEL process in AS11

Since As11 supports both events and services to initiate a SOA composite ( may be having a BPEL process within it), there is always a question around when to use events and when to use service invocation to start the process.

The decision can be based on the following understanding of the events and service patterns.

Events

• Events are suitable for a decoupled integration.
  
• Events are one way messaging (no request response pattern and correlation)
  
• The publisher does not know about the subscribers (there might not be subscribers too)
• The publisher is not blocked for the execution of the subscriptions
• Events support 1:n fan out (multiple subscribers for the same event)
  

Service invocations

• Service invocation is a tight integrations with the service provider
• Service invocation supports request response patterns (sync or async)
• Synchronous service invocation is blocked till the execution of the service completes.
• Async Request response pattern is often supported via WS-adderessing and correlation

Quick Summary of Business Events Support in SOA As11

Oracle's SOA Suite AS11 is a rendezvous of SOA and EDA models. The EDA functionality is served by Business Events Framework (called Event Delivery Network EDN) and Complex Event Process (CEP) are two main components.

EDN: EDN supports a loosely coupled event pub-sub model. From another J2EE server, a publisher can publish the events either programmatically using Java API from a J2EE container or declaratively via ADFbc Entity Objects. These events can be subscribed by zero or more mediator(s) or bpel(s). Both Mediator and BPEL can publish events too. EDN's event pub-sub model supports m:n relations. EDN has been implemented on top of JMS. It supports delivery policies like AtLeastOnce, OneAndOnlyOne, and ExactlyOnce.

EDL: Events are described using EDL (Event Description Language). Each event has a event name as QName and event payload as a xml element. Events carry properties, headers and a payload in runtime.

SCA: We have also made events as a first-class-citizen of SCA. In SCA composite, event publishing and subscribing can be specified.

Subscription: Event subscriptions are defined with event name and (optionally) Xpath based condition filter. While multiple components from one or more composites can subscribe an event, there can be only one subscription per subscribing component.

Testing: You can fire a test event using SOA console in Enterprise Manager (EM)

Monitoring: Events can be monitored by SOA console in EM or http://soaserver:port/soa-infra/events/edn-db-log.html