With WildFly 11 you can now listen to JMX notifications on a server lifecycle events.

A server will now send AttributeChangeNotifications for the attributes RuntimeConfigurationState and RunningState on the object named "jboss.root:type=state".

What does this mean to me ?

There are 2 kinds of events on a WildFly server lifecyle :

* those that concern the state of the model configuration compared to the running configuration : restart-required, reload-required, starting, stopping, stopped and ok.

* those that concern the running state of a server : stopped, starting, pre-suspended, suspended, stopping, suspending, admin_only and normal. Please note that you can only suspend and resume standalone or managed servers instance.

So now you can simply register a javax.management.NotificationListener on "jboss.root:type=state" and get all those notifications.

You can filter on the attribute name to get only those that you are interested in.

Some code

Let's create a simple javax.management.NotificationListener

public class StateNotificationListener implements NotificationListener {

    public static final String RUNTIME_CONFIGURATION_FILENAME = "runtime-configuration-notifications.txt";
    public static final String RUNNING_FILENAME = "running-notifications.txt";
    private final Path targetFile;

    public ControlledStateNotificationListener() {
        this.targetFile = Paths.get("notifications/data").toAbsolutePath();
        init(targetFile);
    }

    protected Path getRuntimeConfigurationTargetFile() {
        return this.targetFile.resolve(RUNTIME_CONFIGURATION_FILENAME);
    }

    protected Path getRunningConfigurationTargetFile() {
        return this.targetFile.resolve(RUNNING_FILENAME);
    }

    protected final void init(Path targetFile) {
        if (!Files.exists(targetFile)) {
            try {
               Files.createDirectories(targetFile);
               if (!Files.exists(targetFile.resolve(RUNTIME_CONFIGURATION_FILENAME))) {
                    Files.createFile(targetFile.resolve(RUNTIME_CONFIGURATION_FILENAME));
               }
               if (!Files.exists(targetFile.resolve(RUNNING_FILENAME))) {
                    Files.createFile(targetFile.resolve(RUNNING_FILENAME));
               }
            } catch (IOException ex) {
                Logger.getLogger(StateNotificationListener.class).error("Problem handling JMX Notification", ex);
            }
        }
    }

    @Override
    public void handleNotification(Notification notification, Object handback) {
        AttributeChangeNotification attributeChangeNotification = (AttributeChangeNotification) notification;
        if ("RuntimeConfigurationState".equals(attributeChangeNotification.getAttributeName())) {
            writeNotification(attributeChangeNotification, getRuntimeConfigurationTargetFile());
        } else {
            writeNotification(attributeChangeNotification, getRunningConfigurationTargetFile());
        }
    }

    private void writeNotification(AttributeChangeNotification notification, Path path) {
        try (BufferedWriter in = Files.newBufferedWriter(path, StandardCharsets.UTF_8, StandardOpenOption.APPEND)) {
            in.write(String.format("%s %s %s %s", notification.getType(), notification.getSequenceNumber(), notification.getSource().toString(), notification.getMessage()));
            in.newLine();
            in.flush();
        } catch (IOException ex) {
            Logger.getLogger(StateNotificationListener.class).error("Problem handling JMX Notification", ex);
        }
    }

}

Now we can just deploy it using a SAR and registering our listener :

mbeanServer.addNotificationListener(new ObjectName("jboss.root:type=state"), new StateNotificationListener(), null, null);

and here we are, ready to listen to all those events.

Using a Java Agent

Another way to register such a listener is to use a Java agent. This requires us to write such an agent like this ( you may find the whole agent source code attached) :

public class WildFlyStateAgent {

    public static void premain(String agentArgs) {
        try {
            final Path runningTargetFile = new File("notifications/data/running-states.txt").toPath();
            final Path runtimeConfigurationTargetFile = new File("notifications/data/runtime-configuration-states.txt").toPath();
            Files.createDirectories(runningTargetFile.getParent());
            Files.deleteIfExists(runningTargetFile);
            Files.createFile(runningTargetFile);
            Files.deleteIfExists(runtimeConfigurationTargetFile);
            Files.createFile(runtimeConfigurationTargetFile);
            final ObjectName name = new ObjectName("jboss.root:type=state");
            final MBeanServer server = ManagementFactory.getPlatformMBeanServer();
            MBeanServerNotificationFilter filter = new MBeanServerNotificationFilter();
            filter.enableAllObjectNames();
            server.addNotificationListener(MBeanServerDelegate.DELEGATE_NAME, new NotificationListener() {
                @Override
                public void handleNotification(Notification notification, Object handback) {
                    MBeanServerNotification mbs = (MBeanServerNotification) notification;
                    if (MBeanServerNotification.REGISTRATION_NOTIFICATION.equals(mbs.getType()) && name.equals(mbs.getMBeanName())) {
                        try {
                            server.addNotificationListener(name, new NotificationListener() {
                                @Override
                                public void handleNotification(Notification notification, Object handback) {
                                    AttributeChangeNotification attributeChangeNotification = (AttributeChangeNotification) notification;
                                    if ("RunningState".equals(attributeChangeNotification.getAttributeName())) {
                                        try (BufferedWriter in = Files.newBufferedWriter(runningTargetFile, StandardCharsets.UTF_8, StandardOpenOption.APPEND)) {
                                            in.write(String.format("%s %s %s %s", notification.getType(), notification.getSequenceNumber(), notification.getSource().toString(), notification.getMessage()));
                                            in.newLine();
                                            in.flush();
                                        } catch (IOException ex) {
                                            throw new RuntimeException(ex);
                                        }
                                    }
                                    else if ("RuntimeConfigurationState".equals(attributeChangeNotification.getAttributeName())) {
                                        try (BufferedWriter in = Files.newBufferedWriter(runtimeConfigurationTargetFile, StandardCharsets.UTF_8, StandardOpenOption.APPEND)) {
                                            in.write(String.format("%s %s %s %s", notification.getType(), notification.getSequenceNumber(), notification.getSource().toString(), notification.getMessage()));
                                            in.newLine();
                                            in.flush();
                                        } catch (IOException ex) {
                                            throw new RuntimeException(ex);
                                        }
                                    }
                                }
                            }, null, null);
                        } catch (InstanceNotFoundException ex) {
                            throw new RuntimeException(ex);
                        }
                    }
                }
            }, filter, null);
        } catch (MalformedObjectNameException | InstanceNotFoundException | IOException ex) {
            throw new RuntimeException(ex);
        }
    }
}

Now we just have to edit the standalone.conf to start our agent when starting the WildFly server instance by changing the $JBOSS_MODULES_SYSTEM_PKGS and adding some $JAVA_OPTS like this :

if [ "x$JBOSS_MODULES_SYSTEM_PKGS" = "x" ]; then
   JBOSS_MODULES_SYSTEM_PKGS="org.jboss.byteman,org.jboss.logmanager,org.wildfly.sample.jmxagent"
fi

JAVA_OPTS="$JAVA_OPTS -Djava.util.logging.manager=org.jboss.logmanager.LogManager -Xbootclasspath/p:$JBOSS_HOME/modules/system/layers/base/org/jboss/logmanager/main/jboss-logmanager-2.0.4.Final.jar -javaagent:/home/ehsavoie/NetBeansProjects/jmxagent/target/jmxagent.jar"