Sonar issue fixes, improved deprecating (java)doc

doc/telemetry.md

@@ -114,17 +114,6 @@ Third the `aer.rabbitmq.worker.*`  metrics are the values as received from the R
 These metrics could also be obtained by directly reading the RabbitMQ api, but specifically for the usage don't require additional logic to get the usage metrics.
 In general these metrics should report the same values, but due to timing (e.g. the moment the measure is taken) there can be differences.
 
-##### Deprecated metrics
-
-The following metrics have been replaced by the more standardized naming mentioned above
-
-| Metric name                                           | type      | description                                                          | Replaced by                                |
-|-------------------------------------------------------|-----------|----------------------------------------------------------------------|--------------------------------------------|
-| `aer.taskmanager.worker_size`<sup>1</sup>             | gauge     | The sum of idle workers + occupied workers.                          | `aer.taskmanager.workerpool.worker.limit`  |
-| `aer.taskmanager.current_worker_size`<sup>1</sup>     | gauge     | The number of workers based on what RabbitMQ reports.                | `aer.rabbitmq.worker.limit`                |
-| `aer.taskmanager.running_worker_size`<sup>1</sup>     | gauge     | The number of workers that are occupied.                             | `aer.taskmanager.workerpool.worker..usage` |
-| `aer.taskmanager.running_client_size`<sup>3</sup>     | gauge     | The number of workers that are occupied for a specific client queue. | `aer.taskmanager.client.queue.usage`       |
-
 ##### Metric attributes
 
 The workers have different attributes to distinguish specific metrics.

source/taskmanager-client/src/main/java/nl/aerius/taskmanager/client/TaskMetrics.java

@@ -61,7 +61,8 @@ public static long longValue(final Map<String, Object> messageMetaData, final St
   }
 
   public static String stringValue(final Map<String, Object> messageMetaData, final String key) {
-    return Optional.ofNullable(messageMetaData.get(key))
+    return Optional.ofNullable(messageMetaData)
+        .map(m -> m.get(key))
         .filter(LongString.class::isInstance)
         .map(t -> new String(((LongString) t).getBytes()))
         .orElse("");

source/taskmanager/src/main/java/nl/aerius/taskmanager/StartupGuard.java

@@ -17,17 +17,18 @@
 package nl.aerius.taskmanager;
 
 import java.util.concurrent.Semaphore;
+import java.util.concurrent.locks.ReentrantLock;
 
 import nl.aerius.taskmanager.adaptor.WorkerSizeObserver;
 
 /**
- * Class to be used at startup. The Scheduler should not start before it is known how many messages are still on the queue.
- * This to register any work that is still on the queue and to properly calculate load metrics.
- * Because the Task Manager is not aware of the tasks already on the queue and therefore otherwise these messages won't be counted in the metrics.
- * This can result in the metrics being skewed, and thereby negatively reporting load metrics.
+ * Class to be used at startup. The Scheduler should not start before the number of messages on the queue is zero.
+ * Because the Task Manager has no information of the tasks already on the queue and therefore there is no tracking information of those messages.
+ * As all tracking information only lives in memory and is reset when the Task Manager is restarted.
  */
 public class StartupGuard implements WorkerSizeObserver {
 
+  private final ReentrantLock lock = new ReentrantLock();
   private final Semaphore openSemaphore = new Semaphore(0);
 
   private boolean open;
@@ -48,11 +49,14 @@ public void waitForOpen() throws InterruptedException {
 
   @Override
   public void onNumberOfWorkersUpdate(final int numberOfWorkers, final int numberOfMessages, final int numberOfMessagesInProgress) {
-    synchronized (openSemaphore) {
+    lock.lock();
+    try {
       if (!open) {
         open = true;
         openSemaphore.release();
       }
+    } finally {
+      lock.unlock();
     }
   }
 }

source/taskmanager/src/main/java/nl/aerius/taskmanager/TaskManager.java

@@ -174,8 +174,6 @@ public TaskScheduleBucket(final QueueConfig queueConfig) throws InterruptedExcep
         workerSizeObserverProxy.addObserver(workerQueueName, wzo);
       }
       workerProducer.start();
-      // Set up metrics
-      WorkerPoolMetrics.setupMetrics(workerPool, workerQueueName);
 
       dispatcher = new TaskDispatcher(workerQueueName, taskScheduler, workerPool);
       executorService.execute(() -> {
@@ -234,7 +232,6 @@ public void addTaskConsumerIfAbsent(final QueueConfig queueConfig) {
       });
     }
 
-
     /**
      * Removes a task consumer with the given queue name.
      *
@@ -250,7 +247,6 @@ public void shutdown() {
       dispatcher.shutdown();
       workerProducer.shutdown();
       taskManagerMetrics.remove(workerQueueName);
-      WorkerPoolMetrics.removeMetrics(workerQueueName);
       taskConsumers.forEach((k, v) -> v.shutdown());
     }