How Stuff Works

Following diagrams are my understanding of the ServiceMix architecture based on a study of the source code. Enjoy – PS.

NMR Flow types

The flow type determines the mechanism by which the Normalized Message Router (NMR) Broker sends messages from one BC/SE to another.

Flow implementation classes

• JBIContainer "flowName" attribute determines the flow type used

• There is only 1 flow per Broker (and 1 Broker per JBIContainer)

• Flow name/class mappings are in the ServiceMix JAR. See META-INF/services/org/servicemix/jbi/nmr/flow

• There are a number of flow implementations. For example: STFlow, SedaFlow, JMSFlow, JCAFlow

Broker send sequence diagram

• The NMR Broker calls sendExchangePacket to deliver a message

• The flow implementation of abstract doSend Method determines how the message sending mechanism works

STFlow

STFlow = "Straight Through" Flow. This is the simplest mechanism. There is no staging or buffering.

sequence diagram

SedaFlow

SEDA = "Staged Event Driven Architecture" Flow. SEDA decomposes a complex, event-driven application into a set of stages connected by queues.

SedaFlow / SedaQueue classes

• There is 1 SedaFlow instance and a number of SedaQueue instances (1 per component)

• The SedaFlow "enqueues" an ME to send a message

• The SedaQueue instance "dequeues" the ME and processes it

• Each SedaQueue holds a concurrent HashMap of MessageExchanges (MEs) to the component. Enqueue/Dequeue is simply put/get of this HashMap

sequence diagram

• SedaQueue instances are lazilly created as needed and referenced in a queueMap

• Each SedaQueue instance runs as JCA1.5 asynchronous Work thread polling the HashMap at fixed intervals

• Having enqueued the ME, the SedaFlow doSend Method may return

• When the SedaQueue Worker (run Method) finds (dequeues) an ME, it processes it in another JCA Worker thread created solely for that purpose

JMSFlow

coming soon