Database Reference
In-Depth Information
Understanding revisions
When a
HelloWorld
composite is deployed to the server, a revision is required
during the deployment. Thus, the service's
Web Services Description Lan-
guage (WSDL)
can be accessed via a URL similar to the following, clearly indic-
ating a revision of "1.0" after the composite name:
However, there may be a case where a new version of the service needs to
be deployed and that this version has a different implementation from the exist-
ing one. Overwriting the existing version may not be the right option as it would
break all client applications that are already utilizing the service. Thus, it makes
sense to deploy the new service using a different revision, such as revision "2.0",
and thus make both the versions available simultaneously. It would, therefore,
be accessible at a different URL:
Now, the old and new services are both available and accessible. Clients ac-
cessing revision 1.0 of the composite may transition to revision 2.0 at their own
pace. If multiple revisions of the same service are deployed, one of them must
be specified as the default revision. This can be specified during deployment
time or changed at runtime. The default revision would thus be accessed at a
revision-independent URL:
Typically, client applications will access the default revision. Revisions are ad-
vantageous in environments where maintaining old and new versions of the
same composite is required, particularly if it involves breaking changes.
As shown in the following screenshot, default revisions are indicated by a green
dot in the list of composites for a given partition. Partitions will be explained in
detail later in this chapter.
