feat(jmc-agent): add handler for retrieving available probe templates

[Josh-Matsuoka]

Small PR to add a handler for retrieving currently available probe templates, this is needed for the Agent Plugin frontend. Also fixes an issue with the notification category for the delete handler and tweaks the way the TargetProbesGetHandler outputs the active probes for the frontend.

Keeping as Draft until I add tests for the new handler

Depends on cryostatio/cryostat-core#156

[mergify]

Pull Request blocked. web-client submodule updates are performed automatically by CI when that repository is updated. Please revert or drop all changes to the web-client submodule from this PR and perform any required frontend work by opening and merging a PR against cryostat-web.

[andrewazores]

Nice, that removal of connection.connect() actually revealed a bug, since I don't think anywhere else in Cryostat actually uses connection.getHandle() like that.

SEVERE: HTTP 500: Cannot invoke "org.openjdk.jmc.rjmx.IConnectionHandle.getServiceOrDummy(java.lang.Class)" because "connectionHandle" is null
io.vertx.ext.web.handler.HttpException: Internal Server Error
Caused by: io.cryostat.net.web.http.api.v2.ApiException: Cannot invoke "org.openjdk.jmc.rjmx.IConnectionHandle.getServiceOrDummy(java.lang.Class)" because "connectionHandle" is null
	at io.cryostat.net.web.http.api.v2.AbstractV2RequestHandler.handle(AbstractV2RequestHandler.java:112)
	at io.cryostat.net.web.http.api.v2.AbstractV2RequestHandler.handle(AbstractV2RequestHandler.java:68)
	at io.vertx.ext.web.impl.BlockingHandlerDecorator.lambda$handle$0(BlockingHandlerDecorator.java:48)
	at io.vertx.core.impl.ContextImpl.lambda$null$0(ContextImpl.java:159)
	at io.vertx.core.impl.AbstractContext.dispatch(AbstractContext.java:100)
	at io.vertx.core.impl.ContextImpl.lambda$executeBlocking$1(ContextImpl.java:157)
	at io.vertx.core.impl.TaskQueue.run(TaskQueue.java:76)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: java.lang.NullPointerException: Cannot invoke "org.openjdk.jmc.rjmx.IConnectionHandle.getServiceOrDummy(java.lang.Class)" because "connectionHandle" is null
	at io.cryostat.core.agent.AgentJMXHelper.<init>(AgentJMXHelper.java:68)
	at io.cryostat.net.web.http.api.v2.TargetProbesGetHandler.lambda$handle$0(TargetProbesGetHandler.java:113)
	at io.cryostat.net.TargetConnectionManager.executeConnectedTask(TargetConnectionManager.java:163)
	at io.cryostat.net.web.http.api.v2.TargetProbesGetHandler.handle(TargetProbesGetHandler.java:109)
	at io.cryostat.net.web.http.api.v2.AbstractV2RequestHandler.handle(AbstractV2RequestHandler.java:102)
	... 10 more

The problem is here, in -core's JFRConnection class:

    public synchronized IConnectionHandle getHandle() {
        return this.handle;
    }

    public synchronized IFlightRecorderService getService()
            throws ConnectionException, IOException, ServiceNotAvailableException {
        if (!isConnected()) {
            connect();
        }
        IFlightRecorderService service = serviceFactory.getServiceInstance(handle);
        if (service == null || !isConnected()) {
            throw new ConnectionException(
                    String.format(
                            "Could not connect to remote target %s",
                            this.connectionDescriptor.createJMXServiceURL().toString()));
        }
        return service;
    }

This could either be fixed in -core by checking for a connection before returning from getHandle(), or it could be fixed in Cryostat's TargetConnectionManager by calling connect() on the connection instance before invoking the connected task on it. I'm inclined to say that doing it in -core is the better fix.

stale

[Josh-Matsuoka]

Fixed the getHandle issue in the core PR, and made a quick adjustment here to accompany it

[github-actions]

This PR/issue depends on:

• fix(jmc-agent): Agent plugin updates and cleanup cryostat-core#156
  By Dependent Issues (🤖). Happy coding!