Brief introduction
Example of scenario with a deployed instance with two elements:
- 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 repeat the action, but in other scenarios it could be different, it depends on 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 "outProperties" to save information related to the deployment process.
"outProperties" is controlled by the participant side, and saved into ACM-r Db by status message (by sendAcElementInfo method). Each participant replica will be synchronized as well.
The examples below are suggestions.
- Below a simple example:
@Override
public void deploy(CompositionElementDto compositionElement, InstanceElementDto instanceElement) throws PfModelException {
if ("DEPLOYED".equals(instanceElement.outProperties().get("state"))) {
// deploy process already done
intermediaryApi.updateAutomationCompositionElementState(instanceElement.instanceId(), instanceElement.elementId(), DeployState.DEPLOYED, null, StateChangeResult.NO_ERROR, "Already Deployed");
return;
}
// deployment process
.......................................
.......................................
// end of the deployment process
if (isDeploySuccess()) {
instanceElement.outProperties().put("state", "DEPLOYED");
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(), null, null, instanceElement.outProperties());
intermediaryApi.updateAutomationCompositionElementState(instanceElement.instanceId(), instanceElement.elementId(), DeployState.DEPLOYED, null, StateChangeResult.NO_ERROR, "Deployed");
} else {
instanceElement.outProperties().put("state", "UNDEPLOYED");
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(), null, null, instanceElement.outProperties());
intermediaryApi.updateAutomationCompositionElementState(instanceElement.instanceId(), instanceElement.elementId(), DeployState.UNDEPLOYED, null, StateChangeResult.FAILED, "Deploy failed!");
}
}
@Override
public void undeploy(CompositionElementDto compositionElement, InstanceElementDto instanceElement) throws PfModelException {
if ("DEPLOYED".equals(instanceElement.outProperties().get("state"))) {
// undeploy process already done
intermediaryApi.updateAutomationCompositionElementState(instanceElement.instanceId(), instanceElement.elementId(), DeployState.UNDEPLOYED, null, StateChangeResult.NO_ERROR, "Already Undeployed");
return;
}
// undeployment process
.......................................
.......................................
// end of the undeployment process
if (isUndeploySuccess()) {
instanceElement.outProperties().put("state", "UNDEPLOYED");
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(), null, null, instanceElement.outProperties());
intermediaryApi.updateAutomationCompositionElementState(instanceElement.instanceId(), instanceElement.elementId(), DeployState.UNDEPLOYED, null, StateChangeResult.NO_ERROR, "Undeployed");
} else {
instanceElement.outProperties().put("state", "DEPLOYED");
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(), null, null, instanceElement.outProperties());
intermediaryApi.updateAutomationCompositionElementState(instanceElement.instanceId(), instanceElement.elementId(), DeployState.DEPLOYED, null, StateChangeResult.FAILED, "Undeploy failed!");
}
}
- Below other suggestion when a process is failed, all elements should repeat the action and it may need some clean up
@Override
public void deploy(CompositionElementDto compositionElement, InstanceElementDto instanceElement) throws PfModelException {
var state = instanceElement.outProperties().get("state");
if ("DEPLOYED".equals(state)) {
// clean up deployment
} else if ("DEPLOYING".equals(state) || "UNDEPLOYING".equals(state)) {
// check and clean up
}
// deployment process
instanceElement.outProperties().put("state", "DEPLOYING");
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(), null, null, instanceElement.outProperties());
.......................................
.......................................
.......................................
// end of the deployment process
if (isDeploySuccess()) {
instanceElement.outProperties().put("state", "DEPLOYED");
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(), null, null, instanceElement.outProperties());
intermediaryApi.updateAutomationCompositionElementState(instanceElement.instanceId(), instanceElement.elementId(), DeployState.DEPLOYED, null, StateChangeResult.NO_ERROR, "Deployed");
} else {
instanceElement.outProperties().put("state", "UNDEPLOYED");
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(), null, null, instanceElement.outProperties());
intermediaryApi.updateAutomationCompositionElementState(instanceElement.instanceId(), instanceElement.elementId(), DeployState.UNDEPLOYED, null, StateChangeResult.FAILED, "Deploy failed!");
}
}
@Override
public void undeploy(CompositionElementDto compositionElement, InstanceElementDto instanceElement) throws PfModelException {
var state = instanceElement.outProperties().get("state");
if ("UNDEPLOYED".equals(state)) {
// clean up undeployment
} else if ("DEPLOYING".equals(state) || "UNDEPLOYING".equals(state)) {
// check and clean up
}
// undeployment process
instanceElement.outProperties().put("state", "UNDEPLOYING");
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(), null, null, instanceElement.outProperties());
.......................................
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// end of the undeployment process
if (isUndeploySuccess()) {
instanceElement.outProperties().put("state", "UNDEPLOYED");
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(), null, null, instanceElement.outProperties());
intermediaryApi.updateAutomationCompositionElementState(instanceElement.instanceId(), instanceElement.elementId(), DeployState.UNDEPLOYED, null, StateChangeResult.NO_ERROR, "Undeployed");
} else {
instanceElement.outProperties().put("state", "DEPLOYED");
intermediaryApi.sendAcElementInfo(instanceElement.instanceId(), instanceElement.elementId(), null, null, instanceElement.outProperties());
intermediaryApi.updateAutomationCompositionElementState(instanceElement.instanceId(), instanceElement.elementId(), DeployState.DEPLOYED, null, StateChangeResult.FAILED, "Undeploy failed!");
}
}