added a few gauges updated on a timer

.gitignore

@@ -0,0 +1,2 @@
+*~
+target/

docker-compose.yml

@@ -0,0 +1,16 @@
+version: '3'
+
+services:
+  keycloak:
+      image: quay.io/keycloak/keycloak:21.0.2
+      environment:
+        KEYCLOAK_ADMIN: admin
+        KEYCLOAK_ADMIN_PASSWORD: admin
+        KC_HTTP_RELATIVE_PATH: /auth
+        KC_HEALTH_ENABLED: true
+        KC_METRICS_ENABLED: true
+      ports:
+        - 8080:8080
+      volumes: 
+        - ./target/keycloak-event-metrics-0.2.1-SNAPSHOT.jar:/opt/keycloak/providers/keycloak-event-metrics.jar
+      command: [ "start-dev" ] 

src/main/java/io/kokuwa/keycloak/metrics/MicrometerEventListenerFactory.java

@@ -1,15 +1,18 @@
 package io.kokuwa.keycloak.metrics;
 
+import com.google.common.collect.ImmutableList;
+import io.micrometer.core.instrument.ImmutableTag;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Tag;
 import javax.enterprise.inject.spi.CDI;
-
 import org.jboss.logging.Logger;
 import org.keycloak.Config.Scope;
 import org.keycloak.events.EventListenerProvider;
 import org.keycloak.events.EventListenerProviderFactory;
 import org.keycloak.models.KeycloakSession;
 import org.keycloak.models.KeycloakSessionFactory;
-
+import org.keycloak.models.utils.KeycloakModelUtils;
-import io.micrometer.core.instrument.MeterRegistry;
+import org.keycloak.timer.TimerProvider;
 
 /**
  * Factory for {@link MicrometerEventListener}, uses {@link MeterRegistry} from CDI.
@@ -18,13 +21,15 @@ import io.micrometer.core.instrument.MeterRegistry;
  */
 public class MicrometerEventListenerFactory implements EventListenerProviderFactory {
 
+  private static final String PROVIDER_ID = "metrics-listener";
+  private static final int INTERVAL = 60 * 1000; //1 MINUTE
 	private static final Logger log = Logger.getLogger(MicrometerEventListener.class);
 	private MeterRegistry registry;
 	private boolean replace;
 
 	@Override
 	public String getId() {
-		return "metrics-listener";
+		return PROVIDER_ID;
 	}
 
 	@Override
@@ -36,6 +41,17 @@ public class MicrometerEventListenerFactory implements EventListenerProviderFact
 	@Override
 	public void postInit(KeycloakSessionFactory factory) {
 		registry = CDI.current().select(MeterRegistry.class).get();
+
+                KeycloakModelUtils.runJobInTransaction(factory, s1 -> {
+                    TimerProvider timer = s1.getProvider(TimerProvider.class);
+                    log.info("Registering gauge update job TimerProvider");
+                    timer.schedule(() -> {
+                        KeycloakModelUtils.runJobInTransaction(s1.getKeycloakSessionFactory(), s2 -> {
+                            log.info("Updating gauges");
+                            updateGauges(s2);
+                          });
+                      }, INTERVAL, PROVIDER_ID);
+                  });
 	}
 
 	@Override
@@ -45,4 +61,49 @@ public class MicrometerEventListenerFactory implements EventListenerProviderFact
 
 	@Override
 	public void close() {}
+
+
+  private Iterable<Tag> tags(String... tags) {
+    if (tags.length % 2 != 0) throw new IllegalStateException("Tag name value pairs must be even"); 
+    ImmutableList.Builder<Tag> builder = new ImmutableList.Builder<Tag>();
+    for (int i = 0;i < tags.length;i+=2) {
+      builder.add(new ImmutableTag(tags[i], tags[i+1]));
+    }
+    return builder.build();
+  }
+    
+  private void updateGauges(KeycloakSession session) {
+    session.realms().getRealmsStream().forEach(realm -> {
+        // keycloak_users = total number of users
+        registry.gauge("keycloak_users",
+                       tags("realm", replace ? realm.getName() : realm.getId()),
+                       session.users().getUsersCount(realm));
+      
+        // keycloak_clients = total number of clients
+        registry.gauge("keycloak_clients",
+                       tags("realm", replace ? realm.getName() : realm.getId()),
+                       realm.getClientsCount());
+
+        // sessions - by client
+
+        realm.getClientsStream().forEach(client -> {
+            // keycloak_active_user_sessions
+            registry.gauge("keycloak_active_user_sessions",
+                           tags("realm", replace ? realm.getName() : realm.getId(),
+                                "client", replace ? client.getClientId() : client.getId()),
+                           session.sessions().getActiveUserSessions(realm, client));
+            // keycloak_active_client_sessions
+            registry.gauge("keycloak_active_client_sessions",
+                           tags("realm", replace ? realm.getName() : realm.getId(),
+                                "client", replace ? client.getClientId() : client.getId()),
+                           session.sessions().getActiveClientSessionStats(realm,false).get(client.getId()));
+
+            // keycloak_offline_sessions
+            registry.gauge("keycloak_offline_sessions",
+                           tags("realm", replace ? realm.getName() : realm.getId(),
+                                "client", replace ? client.getClientId() : client.getId()),
+                           session.sessions().getOfflineSessionsCount(realm, client));
+          });
+      });    
+  }
 }