ARTEMIS-4456 Register metrics plugin

Author: brusdev

artemis-server/src/main/java/org/apache/activemq/artemis/core/server/impl/ActiveMQServerImpl.java

@@ -3367,6 +3367,10 @@ synchronized boolean initialisePart1(boolean scalingDown) throws Exception {
          registerBrokerPlugins(getBrokerPlugins());
       }
 
+      if (configuration.getMetricsConfiguration() != null && configuration.getMetricsConfiguration().getPlugin() != null) {
+         configuration.getMetricsConfiguration().getPlugin().registered(this);
+      }
+
       return true;
    }
 

artemis-server/src/main/java/org/apache/activemq/artemis/core/server/metrics/ActiveMQMetricsPlugin.java

@@ -20,10 +20,19 @@
 import java.util.Map;
 
 import io.micrometer.core.instrument.MeterRegistry;
+import org.apache.activemq.artemis.core.server.ActiveMQServer;
 
 public interface ActiveMQMetricsPlugin extends Serializable {
 
    ActiveMQMetricsPlugin init(Map<String, String> options);
 
    MeterRegistry getRegistry();
+
+   /**
+    * The plugin has been registered with the server
+    *
+    * @param server The ActiveMQServer the plugin has been registered to
+    */
+   default void registered(ActiveMQServer server) {
+   }
 }

artemis-server/src/main/java/org/apache/activemq/artemis/core/server/metrics/plugins/SimpleMetricsPlugin.java

@@ -20,6 +20,7 @@
 
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+import org.apache.activemq.artemis.core.server.ActiveMQServer;
 import org.apache.activemq.artemis.core.server.metrics.ActiveMQMetricsPlugin;
 
 /**
@@ -31,6 +32,8 @@ public class SimpleMetricsPlugin implements ActiveMQMetricsPlugin {
 
    private Map<String, String> options;
 
+   private ActiveMQServer server;
+
    @Override
    public ActiveMQMetricsPlugin init(Map<String, String> options) {
       this.meterRegistry = new SimpleMeterRegistry();
@@ -43,7 +46,16 @@ public MeterRegistry getRegistry() {
       return meterRegistry;
    }
 
+   @Override
+   public void registered(ActiveMQServer server) {
+      this.server = server;
+   }
+
    public Map<String, String> getOptions() {
       return options;
    }
+
+   public ActiveMQServer getServer() {
+      return server;
+   }
 }

tests/integration-tests/src/test/java/org/apache/activemq/artemis/tests/integration/plugin/MetricsPluginTest.java

@@ -270,6 +270,12 @@ public void testMessageCountWithPaging() throws Exception {
       checkMetric(getMetrics(), "artemis.message.count", "queue", queueName, Double.valueOf(messageCount * 2));
    }
 
+   @Test
+   public void testMetricsPluginRegistration() {
+      assertEquals(SimpleMetricsPlugin.class, server.getConfiguration().getMetricsConfiguration().getPlugin().getClass());
+      assertEquals(server, ((SimpleMetricsPlugin)server.getConfiguration().getMetricsConfiguration().getPlugin()).getServer());
+   }
+
    public Map<Meter.Id, Double> getMetrics() {
       return getMetrics(server);
    }