merge: #9294

9294: Add actor metrics r=Zelldon a=Zelldon

## Description

As discussed here https://camunda.slack.com/archives/C037RS2JHB8/p1651668160788749 add new actor metrics but no new panels for now. 

Details:

- Add counter for actorTask execution
- Add histogram to observe actorTask execution

Currently starting a benchmark to verify whether metrics are exported as expected.

I will create a separate PR for the atomix executors.

`@npepinpe` I'm not sure whether it fulfills all requirements for #9282 I will remove my assignment then. 



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## Related issues

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related #9282 



Co-authored-by: Christopher Zell <zelldon91@googlemail.com>

util/pom.xml

@@ -20,6 +20,10 @@
       <groupId>org.agrona</groupId>
       <artifactId>agrona</artifactId>
     </dependency>
+    <dependency>
+      <groupId>io.prometheus</groupId>
+      <artifactId>simpleclient</artifactId>
+    </dependency>
 
     <dependency>
       <groupId>org.slf4j</groupId>

util/src/main/java/io/camunda/zeebe/util/sched/ActorMetrics.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH under
+ * one or more contributor license agreements. See the NOTICE file distributed
+ * with this work for additional information regarding copyright ownership.
+ * Licensed under the Zeebe Community License 1.1. You may not use this file
+ * except in compliance with the Zeebe Community License 1.1.
+ */
+package io.camunda.zeebe.util.sched;
+
+import io.prometheus.client.Counter;
+import io.prometheus.client.Histogram;
+
+final class ActorMetrics {
+
+  private static final Histogram EXECUTION_LATENCY =
+      Histogram.build()
+          .namespace("zeebe")
+          .name("actor_task_execution_latency")
+          .help("Execution time of a certain actor task")
+          .labelNames("actorName")
+          .register();
+
+  private static final Counter EXECUTION_COUNT =
+      Counter.build()
+          .namespace("zeebe")
+          .name("actor_task_execution_count")
+          .help("Number of times a certain actor task was executed successfully")
+          .labelNames("actorName")
+          .register();
+
+  Histogram.Timer startExecutionTimer(final String name) {
+    return EXECUTION_LATENCY.labels(name).startTimer();
+  }
+
+  void countExecution(final String name) {
+    EXECUTION_COUNT.labels(name).inc();
+  }
+}

util/src/main/java/io/camunda/zeebe/util/sched/ActorThread.java

@@ -42,6 +42,7 @@ public class ActorThread extends Thread implements Consumer<Runnable> {
   protected final ActorTimerQueue timerJobQueue;
   protected ActorTaskRunnerIdleStrategy idleStrategy = new ActorTaskRunnerIdleStrategy();
   ActorTask currentTask;
+  private final ActorMetrics actorMetrics = new ActorMetrics();
   private final CompletableFuture<Void> terminationFuture = new CompletableFuture<>();
   private final ActorClock clock;
   private final int threadId;
@@ -77,7 +78,12 @@ private void doWork() {
 
     if (currentTask != null) {
       try {
-        executeCurrentTask();
+        final var actorName = currentTask.actor.getName();
+        try (final var timer = actorMetrics.startExecutionTimer(actorName)) {
+          executeCurrentTask();
+        }
+        actorMetrics.countExecution(actorName);
+
       } finally {
         taskScheduler.onTaskReleased(currentTask);
       }