Brief introduction
Example of scenario with a deployed instance with two element:
- user call undeploy command
- first instance element success with UNDEPLOYED state
- second instance element fail with DEPLOYED state
- user call undeploy command again
- first instance element does not know that the element is already UNDEPLOYED
Add support for the participant to understand what was the last state.
Additional comments
It is important to make distinction between the state of the instance/element in the flow, and the state of the application involved. A deployed element means that a participant has completed a deploy action, and should not be confused with a deployed application.
There are scenarios where it make sense when a process is failed, all elements should be repeat fully, by in other scenarios could de different, it depend of the context. Anyway a participant could implement idempotent operations.
The responsibility to know what it needs to be done is delegated to the participant.
When a participant cannot implement idempotent operations, in order to cover the scenario with failed process with more than one element involved, it has to know what was the previous state.
Solutions
A simple solution from participant side is that it can use "useState" or "operationalState" to save information related to the deployment process.
Into the participant implementation it can send the completition of the process by sendAcElementInfo method.
To support the participant implementation we can add "useState" and "operationalState" into the InstanceElementDto:
public record InstanceElementDto(UUID instanceId, UUID elementId, ToscaServiceTemplate toscaServiceTemplateFragment,
Map<String, Object> inProperties, Map<String, Object> outProperties, String operationalState, String useState) {
}
Below an example with operationalState where the process should not be repeated:
@Override
public void deploy(CompositionElementDto compositionElement, InstanceElementDto instanceElement)
throws PfModelException {
if ("DEPLOYED".equals(instanceElement.operationalState())) {
// deploy process already done
intermediaryApi.updateAutomationCompositionElementState(instanceId, elementId,
DeployState.DEPLOYED, null, StateChangeResult.NO_ERROR, "Already Deployed");
return;
}
// deployment process
.......................................
.......................................
// end of the deployment process
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(),
"", "DEPLOYED", instanceElement.outProperties());
intermediaryApi.updateAutomationCompositionElementState(instanceId, elementId,
DeployState.DEPLOYED, null, StateChangeResult.NO_ERROR, "Deployed");
}
@Override
public void undeploy(CompositionElementDto compositionElement, InstanceElementDto instanceElement)
throws PfModelException {
if ("UNDEPLOYED".equals(instanceElement.operationalState())) {
// undeploy process already done
intermediaryApi.updateAutomationCompositionElementState(instanceId, elementId,
DeployState.UNDEPLOYED, null, StateChangeResult.NO_ERROR, "Already Undeployed");
return;
}
// undeployment process
.......................................
.......................................
// end of the undeployment process
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(),
"", "UNDEPLOYED", instanceElement.outProperties());
intermediaryApi.updateAutomationCompositionElementState(instanceId, elementId,
DeployState.UNDEPLOYED, null, StateChangeResult.NO_ERROR, "Undeployed");
}