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Subject: [OASIS Issue Tracker] Commented: (TOSCA-32) Action transfer between source nodes and target nodes
[ http://tools.oasis-open.org/issues/browse/TOSCA-32?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=30796#action_30796 ]
Thomas Spatzier commented on TOSCA-32:
---------------------------------------
Two observations when looking at the proposal in the chart deck:
(1) Having sourceAction and targetAction being URIs that need to be defined, this kind of contradicts to the notion of interfaces defined for Node Types. The source and target of a relationship are Node Templates of a specific Node Type, and it should only be possible to invoke operations (actions) defined in their interfaces. Otherwise, having general "actions" like suspend, start, delete ... might not be supported on all nodes.
(2) While there are some nice features we could get out of such a solution, I am much afraid of the complexity this can introduce. This approach can lead to chains of actions that can get fired off throughout a potentially complex topology of a service which will soon be hard to overlook. I.e. changing one tiny thing in some point might escalate as complex actions flows on a number of components. The original idea in TOSCA was that the execution of flows of operations would be defined in plans, not in action propagation annotated in the topology.
I agree that having the current "cascadingDeletion" attribute is already one step in such a direction, but not a full solution and people will want to do more. However, thinking about the complexity that is introduces (see #2) I would even be inclined to drop the cascadingDeletion attribute completely and encourage the use of plans for such functionality.
> Action transfer between source nodes and target nodes
> -----------------------------------------------------
>
> Key: TOSCA-32
> URL: http://tools.oasis-open.org/issues/browse/TOSCA-32
> Project: OASIS Topology and Orchestration Specification for Cloud Applications (TOSCA) TC
> Issue Type: Improvement
> Reporter: Paul Zhang
>
> cascadingDeletion is used to indicate that if the target instance is deleted automatically with the deletion of the source instance.
> There may be some other cases that one action of the target instance leads to one action of the source instance, where the actions may be not restricted to the deletion action. For example, two Node Templates describing an AppServer and a DBServer are associated by a Relationship Template with the relationship type "Integrated with", where the DBServer is the target node and the AppServer is the source node. Developers may want to indicate in Relationship Type that the DBServer is suspended automatically when the AppServer is suspended. Furthermore, in some cases, suspending a target instance can also lead to the action of suspending the source instance.
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