exports dropwizard-metrics to prometheus format

Signed-off-by: Max Thonagel <12283268+thoniTUB@users.noreply.github.com>

backend/pom.xml

@@ -389,5 +389,25 @@
             <artifactId>ngdbc</artifactId>
             <version>2.17.10</version>
         </dependency>
+        <dependency>
+            <groupId>io.prometheus</groupId>
+            <artifactId>simpleclient_dropwizard</artifactId>
+            <version>0.16.0</version>
+        </dependency>
+        <dependency>
+            <groupId>io.prometheus</groupId>
+            <artifactId>prometheus-metrics-simpleclient-bridge</artifactId>
+            <version>1.2.1</version>
+        </dependency>
+        <dependency>
+            <groupId>io.prometheus</groupId>
+            <artifactId>prometheus-metrics-exporter-servlet-jakarta</artifactId>
+            <version>1.2.1</version>
+        </dependency>
+        <dependency>
+            <groupId>io.prometheus</groupId>
+            <artifactId>prometheus-metrics-core</artifactId>
+            <version>1.2.1</version>
+        </dependency>
     </dependencies>
 </project>

backend/src/main/java/com/bakdata/conquery/Conquery.java

@@ -9,6 +9,7 @@
 import com.bakdata.conquery.commands.ShardNode;
 import com.bakdata.conquery.io.jackson.Jackson;
 import com.bakdata.conquery.io.jackson.MutableInjectableValues;
+import com.bakdata.conquery.metrics.prometheus.PrometheusBundle;
 import com.bakdata.conquery.mode.Manager;
 import com.bakdata.conquery.mode.ManagerProvider;
 import com.bakdata.conquery.mode.cluster.ClusterManagerProvider;
@@ -82,6 +83,8 @@ public void initialize(Bootstrap<?> bootstrap) {
 						bootstrap.getConfigurationSourceProvider(), StringSubstitutor.createInterpolator()));
 			}
 		});
+
+		bootstrap.addBundle(new PrometheusBundle());
 	}
 
 	@Override

backend/src/main/java/com/bakdata/conquery/metrics/prometheus/PrometheusBundle.java

@@ -0,0 +1,28 @@
+package com.bakdata.conquery.metrics.prometheus;
+
+import com.bakdata.conquery.models.config.ConqueryConfig;
+import io.dropwizard.core.ConfiguredBundle;
+import io.dropwizard.core.setup.Bootstrap;
+import io.dropwizard.core.setup.Environment;
+import io.prometheus.client.CollectorRegistry;
+import io.prometheus.client.dropwizard.DropwizardExports;
+import io.prometheus.metrics.exporter.servlet.jakarta.PrometheusMetricsServlet;
+import io.prometheus.metrics.simpleclient.bridge.SimpleclientCollector;
+import org.eclipse.jetty.servlet.ServletHolder;
+
+public class PrometheusBundle implements ConfiguredBundle<ConqueryConfig> {
+
+	@Override
+	public void initialize(Bootstrap<?> bootstrap) {
+		// Init simple_client https://www.robustperception.io/exposing-dropwizard-metrics-to-prometheus/
+		CollectorRegistry.defaultRegistry.register(new DropwizardExports(bootstrap.getMetricRegistry()));
+		// Init client_java bridge: https://prometheus.github.io/client_java/migration/simpleclient/
+		SimpleclientCollector.builder().register();
+	}
+
+	@Override
+	public void run(ConqueryConfig configuration, Environment environment) throws Exception {
+
+		environment.getAdminContext().addServlet(new ServletHolder(new PrometheusMetricsServlet()), "/metrics-prometheus");
+	}
+}