Taking Care – Error Handling - Applied SOA Patterns on the Oracle Platform - page 479

sources, essential for the business operation environment. The EH com-
ponent must not only be lightweight, but the physical components should
be separated as well to reduce the additional burden on EH. Obviously,
the Retry / Continue / Cancel default resolutions are properties of
OFM service engines (OSB/SCA), and the basic compensation mechan-
isms are attached to BPEL. However, log consolidation jobs, complex
processing of events using patterns, instances of composition controllers,
and running EH-related compositions can be moved to the separate envir-
onment.
• Next and probably the main EH requirement is the Error Handling automation. In
the previous bullet point, we already mentioned the basic resolution operations
based on primitive policies, but what we really are looking for is the automation
of complex compensations, triggered by irregularities in dynamic compositions.
Logically, compensation of such compositions should also be dynamic, which
makes this task quite difficult. If service composition error classifications are
covered diligently with all the necessary details, dynamic compensation is achiev-
able in various ways: through the standard OFM Error Hospital and/or custom
compensation execution plans similar to what we discussed in Chapter 3 , Build-
ing the Core - Enterprise Business Flows , and Chapter 4 , From Traditional In-
tegration to Composition - Enterprise Business Services , which are dedicated to
synchronous and asynchronous composition controllers.
• Finally, if dynamic resolution is impossible (too late or too complex), manual res-
olution is the only option.
Generic Audit requirements in OFM are covered by Audit Framework for any application,
included in the Audit policy (yes, another policy), using two-phase event propagation with
optional event filtering. Any Audit-enabled application (Java running on WLS or a web
app on an HTTP server) can dump Audit data using an Audit API to local storages called
bus-stops. In the second phase, an Audit loader agent will upload dumped data to the cent-
ralized DB for Log Centralization. In some cases, dispersed bus-stops will suffice, but
then you will miss the analytical capabilities that are provided by the Oracle BI Publisher
connected to the central DB.
These five major requirements all together present the complete scope of EH that is cap-
able of resolving most SOA errors with reasonably reduced pressure on Ops task forces.
Naturally, the complexity of the recovery operations will not disappear only with the real-
ization of what has to be done; to make it happen, quite a considerable amount of work
must be done during the service design phase and during the initial exception testing
phase in the dev environment.