Database Reference
In-Depth Information
Pattern
Problem
Implementation
The advantage of this pattern implementation is that in Coherence, you
do not need to wrap objects into messages, that is, you can skip serial-
ization operations; you use the same distributed infrastructure around
your applications without establishing a new one.
Although the main purpose of Coherence is different than just being a
distributed hubless SAF, some of us who experienced troubles with the
original WLS will agree that SAF greatly appreciates this pattern im-
plementation. Old JMSes and AQs can definitely perform the same
task cheaply in all ways; still, this pattern is the foundation of the next
one.
One word of caution, which is common for all object distribution pat-
terns: plan the distribution path carefully between your nodes and
place the aggregation nodes close to the processing nodes for better
throughput.
Yes, Coherence is the cache we need and the change of objects' state
will not go unnoticed with a properly arranged invalidation strategy (if
you do not know which one to use, go for Listen Auto). Remember the
last figure from the previous paragraph? Coherence is the closest com-
panion of Oracle Event Processing and can provide the following:
If you want something done fast, do it yourself and do
it in cache. If your service component can put the up-
dated object into a distributed cache, then it would be
the fastest way possible to propagate the event notifica-
tion. Thus, the need for cache in events processing is
justified.
The Event
Distribution
pattern
(EDN)
•
Five types of channels for files, errors, and all types of
caches, both local and distributed.
•
Guaranteed delivery of events. No events losses.
This pattern sets the necessary infrastructure for the next pattern in
line.
As the name suggests, data is pushed from the place where changes oc-
curred to all the nodes that are configured to be notified. This is a bit
more than a pattern; it's an entire framework within Coherence that
provides the following types of object pushes:
How can you keep all the objects in all the Grid nodes
synchronized in the most fastest and reliable way? How
can you propagate the changes from one cluster to an-
other?
The Push
Replication
pattern
•
active-passive
•
active-active
•
hub-and-spoke
•
multi-master
•
centralized replication
We touched upon some of these aspects while discussing the three pos-
sible distribution models and ways of data invalidation.
The following table includes Coherence Object Processing patterns:
Pattern
Problem
Implementation
This is a distributed version of the classic Command pattern, and the code
presented in the incubator is quite self explanatory. The executable method
provided by the Command interface simply called
execute
, which requires
The Com-
mand pat-
tern
An operation on a certain object that should be
executed possibly several times (or none) must be
represented as an executable object called Com-
Search WWH ::
Custom Search