Database Reference
In-Depth Information
•
Rule 7
: Maintain strict control on the ErM components footprint on Services and
Compositions. As a logical outcome of rule 3, EH decentralization or service de-
composition (if we assume Error Handler as a service utility type) will reduce an
exception-handling footprint on the service infrastructure. Depending on your
hardware specs and daily business workload, you will set thresholds for EH activ-
ities such as 5 percent CPU, 10 percent RAM, and 10 percent of total threads (just
an example).
•
Rule 8
: Apply the
Redundant Implementation
pattern on critical elements of
ErM. Redundant implementation of elements of the SOA infrastructure (WLS
Nodes and Node manager, and SAN RAC DB) is an absolute must for a resilient
HA infrastructure; however, from the EH standpoint, it is also prudent to consider
a separate node for ErM SB.
•
Rule 9
: Provide alternative execution paths for business-critical service composi-
tions. You cannot fix faulty OFM using the same OFM.
Automated Recovery
Tool (ART)
, or whatever you call it, must be in the utility service layer with a
very shallow technical infrastructure and a maximum of one or two service en-
gines, at least part of it. Just think of this: if an airplane loses its hydraulics, usu-
ally it is doomed as it cannot steer. The bitter irony is that there are still plenty of
means to keep the plane safe and maneuverable: we could still have the engine's
thrust and use it; alternatively, inbound air flows could power a small generator
for elevator/rudder servos. Why is it not implemented? Actually it is, but only for
some special (mostly military) cases because it's rather expensive. Is it also ex-
pensive in SOA? Not at all! We have presented universal XML EPs, and we
clearly demonstrated how they can be executed by different engines (BPEL, JEE,
XMLDB). So you have it already. Additionally, consider Dual Protocols for help-
ing different engines consume EP and messages (for instance, OraDB can con-
sume an HTTP call more easily than HTTP/SOAP; although, SOAP is not an is-
sue either). Sync/Async pairs are always good, especially with Oracle AQ.
•
Rule 10
: Avoid SPOF on MetadataStore and provide alternative means to access
it. Metadata Centralization, like with any type of centralization, has a natural
flaw: SPOF. Its weak point is
Inventory Endpoint
, which is used by
Execu-
tionPlanLookupService
in our design (the same is true for any design). In
addition Service Grid and Redundant Implementation, consider the dual storage
type for your Metadata Storage in ESR. Technically, it's a service data replication
(we can assume service metadata elements that are consumed by SB as its sole
data) for execution plans. The realization of this design rule is exceedingly
simple; in fact, you have it already. As you will remember, initially we implemen-
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