[rules-users] Continuous deployment of rules/vetoing changesets

[Gustaf Cele]

Hi,

I have a Guvnor server (5.4.0.Final) which provides rules to a client (which itself is an EJB server app) using KnowledgeAgents to get hold of rule updates. The knowledge agents are started with changeset XMLs on the classpath which point at my Guvnor instance.

The KnowledgeAgents are set up thus:

    ResourceFactory.getResourceChangeNotifierService().start();
    ResourceFactory.getResourceChangeScannerService().start();
    KnowledgeAgent knowledgeAgent = KnowledgeAgentFactory.newKnowledgeAgent(agentName);
    knowledgeAgent.monitorResourceChangeEvents(true);
    Resource resource = ResourceFactory.newClassPathResource(changeSetResourcePath, getClass());
    knowledgeAgent.applyChangeSet(resource);
    ResourceFactory.getResourceChangeNotifierService().start();
    ResourceFactory.getResourceChangeScannerService().start();

And the changesets look like this (xsd stuff removed for brevity):

<change-set>
    <add>
        <resource username="ruleclient" password="hunter2" basicAuthentication="enabled"
           source="http://guvnorhost/drools-guvnor/org.drools.guvnor.Guvnor/package/my.package/LATEST"
           type="PKG" />
    </add>
</change-set>

As you can see, we use LATEST because we want continuous deployment of our rules. Change a rule, build the package, and have the connected KnowledgeAgents updated with the new rule. This works very well - a bit too well, unfortunately. We have a comprehensive test suite, and every now and then, you'll check in a rule that breaks a test. We want to prevent any changes to our rules from being propagated to the clients until all the tests succeed, and this is where we're stuck.

We've tried using a KnowledgeAgentEventListener which throws an exception when it detects test failures:

    public class VetoListener extends DefaultKnowledgeAgentEventListener {
        @Override
        public void beforeChangeSetApplied(BeforeChangeSetAppliedEvent event) {
            if (!allTestsPass()) {
                throw new RuntimeException("tests failed, not applying change set");
            }
        }

        boolean allTestsPass(){
            // Get test results from ${guvnor_url}/org.drools.guvnor.Guvnor/package/my.package/LATEST/SCENARIOS
            // and check if there were any failures
        }
    }
    // Usage:
    knowledgeAgent.addEventListener(new VetoListener());

This does prevent the new changeset from being applied, but it also seems to kill the thread polling for new changes entirely. Restarting the ResourceChange{Scanner,Notifier}Services doesn't help.

I've also tried modifying the event's changeset (I know you shouldn't), but it doesn't stop the changes from being applied:

    public void beforeChangeSetApplied(BeforeChangeSetAppliedEvent event) {
        if (!allTestsPass()) {
            event.getChangeSet().getResourcesModified().clear();
            // ... and clear all the other collections you can get from event.getChangeSet()
        }
    }

So, what I wonder is if there is any way of preventing a changeset from being applied to a KnowledgeAgent's knowledge base when there are failing test scenarios, but which applies updates as soon as all tests succeed? More generally, I'm looking for something with fewer manual steps than run tests-make snapshot-publish, and in particular I want to ensure you never publish a package when there are tests failing, and it should preferably not require any changes outside of Guvnor to get out new rules to the client app. Any ideas?

Thanks in advance,

/g

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