feat: Add a prometheus /metrics endpoint. (#517)

* chore: Update jicoco.
* feat: Port some metrics to prometheus.
* chore: Bump jetty.
* feat: Add a /metrics endpoint for prometheus.
* feat: Port most stats to metrics.

pom.xml

@@ -22,8 +22,8 @@
     <smack.version>4.4.6</smack.version>
     <jxmppVersion>1.0.3</jxmppVersion>
     <!-- Match jicoco's jetty version. -->
-    <jicoco.version>1.1-107-gfb316f8</jicoco.version>
-    <jetty.version>11.0.10</jetty.version>
+    <jicoco.version>1.1-133-g768ef2e</jicoco.version>
+    <jetty.version>11.0.14</jetty.version>
   </properties>
 
   <dependencies>
@@ -435,6 +435,12 @@
       <version>1.6</version>
       <scope>test</scope>
     </dependency>
+      <dependency>
+          <groupId>org.jitsi</groupId>
+          <artifactId>jicoco-metrics</artifactId>
+          <version>${jicoco.version}</version>
+          <scope>compile</scope>
+      </dependency>
   </dependencies>
 
   <build>

src/main/java/org/jitsi/jigasi/metrics/JigasiMetricsContainer.java

@@ -0,0 +1,31 @@
+/*
+ * Jigasi, the JItsi GAteway to SIP.
+ *
+ * Copyright @ 2024 - present 8x8, Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jitsi.jigasi.metrics;
+
+import io.prometheus.client.*;
+import org.jitsi.metrics.*;
+
+public class JigasiMetricsContainer extends MetricsContainer
+{
+    public final static JigasiMetricsContainer INSTANCE = new JigasiMetricsContainer();
+
+    private JigasiMetricsContainer()
+    {
+        super(CollectorRegistry.defaultRegistry, "jitsi_jigasi");
+    }
+}

src/main/java/org/jitsi/jigasi/rest/AbstractJettyBundleActivator.java

@@ -377,9 +377,16 @@ protected Server initializeServer(BundleContext bundleContext)
         server.addConnector(connector);
 
         Handler handler = initializeHandler(bundleContext, server);
+        Handler metricsHandler = new MetricsHandler();
 
+        HandlerCollection handlers = new HandlerCollection();
         if (handler != null)
-            server.setHandler(handler);
+        {
+            handlers.addHandler(handler);
+        }
+        handlers.addHandler(metricsHandler);
+
+        server.setHandler(handlers);
 
         return server;
     }

src/main/java/org/jitsi/jigasi/rest/MetricsHandler.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright @ 2024 - present, 8x8 Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jitsi.jigasi.rest;
+
+import io.prometheus.client.exporter.common.*;
+import jakarta.servlet.*;
+import jakarta.servlet.http.*;
+import org.eclipse.jetty.server.*;
+import org.eclipse.jetty.server.handler.*;
+import org.jitsi.jigasi.metrics.*;
+import org.jitsi.jigasi.stats.*;
+
+import java.io.*;
+
+public class MetricsHandler extends AbstractHandler
+{
+    @Override
+    public void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response)
+            throws IOException, ServletException
+    {
+        if ("/metrics".equals(target))
+        {
+            String accept = request.getHeader("Accept");
+
+            Statistics.updateMetrics();
+
+            String responseBody;
+            if (accept != null && accept.startsWith("application/openmetrics-text"))
+            {
+                responseBody = JigasiMetricsContainer.INSTANCE.getPrometheusMetrics(
+                        TextFormat.CONTENT_TYPE_OPENMETRICS_100);
+                response.setContentType(TextFormat.CONTENT_TYPE_OPENMETRICS_100);
+            }
+            else if (accept != null && accept.startsWith("text/plain"))
+            {
+                responseBody = JigasiMetricsContainer.INSTANCE.getPrometheusMetrics(TextFormat.CONTENT_TYPE_004);
+                response.setContentType(TextFormat.CONTENT_TYPE_004);
+            }
+            else
+            {
+                responseBody = JigasiMetricsContainer.INSTANCE.getJsonString();
+                response.setContentType(RESTUtil.JSON_CONTENT_TYPE_WITH_CHARSET);
+            }
+
+            Writer writer = response.getWriter();
+            writer.write(responseBody);
+            response.setStatus(200);
+        }
+    }
+}