From Traditional Integration to Composition – Enterprise Business Services - Applied SOA Patterns on the Oracle Platform - page 261

Detailed analysis - functional decomposition
The Synchronous Composition Controller can receive service consumer calls from two dir-
ections—from Composition Initiator (Application Sender), optionally through the Adapter
framework, or from the EBF/SCA master Composition Controller. In the case of a syn-
chronous interchange pattern, we could perform all operations in OSB without involving
the SCA business flows.
We really should do that, because even synchronous logic can be quite complex. Do not let
your enterprise service collaboration layer (or EBS framework) turn into a full-scale or-
chestration! We have started with a demonstration of the Proxy capability of ESB, and we
would like to repeat that decoupling again. It is probably the most important role of ESB
and we would perform transformation, validation, and protocol bridging (which we can rel-
atively easily implement on the Adapter level, which is not always ESB) only after that.
Synchronous Composition Controller should operate only with simple and linear routing
slips (execution plans), with a number of steps not more than 10 (this is quite an empirical
figure). Of course, the limit for the number of invocations should be set according to your
operational environment / computing power.
Note
Let's do the simplest math. You certainly have three fully equipped network zones, namely
DB, APP, and integration, in your technical infrastructure. Ping integration from the DB.
Most probably, you will get no less than 2 ms. Even the simplest pass-through Proxy will
have the same ping interpretation period of 2 ms. We can expect double or more from util-
ity services implementing VETRO patterns in OSB. With full logging, 10 consecutive in-
vocations can have up to 300 ms of operational time in OSB alone. Be careful about prom-
ising something faster than that.
In the case of a linear sequential synchronous process, inbound and outbound functional
parts of OSB will be reduced to the same technical layer that acts as a Service Broker with
intermediate routing and asynchronous queuing, if necessary. Here, the main difference
with the Message Broker will be the complete reliance on the Proxy Service pattern imple-
mentation for true decoupling.
Now, we will summarize the challenges of ESB's functional decomposition.