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ated, so the individual legacy adapter will just send a clear message to Audit (the
orange line).
At the same time, when Adapter-Aggregator is based on an agnostic composition
controller, then exception handling should also be agnostic with extraction of res-
olution action from Service Repository. We should do this with caution, not over-
loading the SR endpoint with requests that involve trivial responses (OSB can
perfectly handle retries with predefined intervals). The advantage of this approach
is that you can monitor a controller's state (active or down) more proactively,
without the need of having an additional heartbeat and external monitoring (al-
though, it is inevitable for a passive adapter and some other components in the
underlying frameworks). Other (additional) reasons could be that the ABCS layer
is down, there is a network/firewall issue, file location is detached, the queue is
unavailable, load balancer is (mis)configured, and the server (node) is down.
2. The next error situation:
data extracted and assembled on the
north side, but transformation from ABO1 to EBO failed
.
The potential reasons for this can be that the XQuery statement is not available,
the execution of XQuery returns a business fault, and business data is inconsist-
ent. Here, we cannot blame the application-composition initiator for all these er-
rors; if the transformation descriptor is not available, we might have severe prob-
lems with the Enterprise Repository. Recovery options are still limited, but the
severity of this problem is very high. If an adapter supports asynchronous com-
munications, the recovery operation will not involve data retransmission from the
source. Technically, this error could be related to misconfiguration or erroneous
installation, so it can be recognized at earlier stages.
3. When business data is invalid, we should stop processing immediately and store
the inbound message in an Audit log for further investigations. The application
source should be informed accordingly.
4. What if we get an exception in ErM? In this case, the ErM composition controller
will not be able to invoke compensation flows or return names/code of resolution
actions to individual components. This problem is quite similar to the situation
where the master composition controller fails. (To avoid possible misunderstand-
ings, the main composition controller and the EH composition controller are dif-
ferent instances of the same agnostic composition controller; both of them are
based on the SOA pattern and promote Reuse and Composability. In order to re-
duce the EH footprint, you could decide to physically separate them on different
WLS nodes.) Most commonly, this situation is related to the missing/inaccessible
routing slip (execution plan). This is a highly critical situation, and a warning will
be issued together with a proper Audit.
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