diff --git a/src/main/java/org/elasticsearch/cluster/service/InternalClusterService.java b/src/main/java/org/elasticsearch/cluster/service/InternalClusterService.java
index 82f3116b32a..8e1ce7a0e2c 100644
--- a/src/main/java/org/elasticsearch/cluster/service/InternalClusterService.java
+++ b/src/main/java/org/elasticsearch/cluster/service/InternalClusterService.java
@@ -32,8 +32,8 @@ import org.elasticsearch.cluster.metadata.ProcessClusterEventTimeoutException;
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.node.DiscoveryNodeService;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
-import org.elasticsearch.cluster.routing.RoutingTable;
 import org.elasticsearch.cluster.routing.OperationRouting;
+import org.elasticsearch.cluster.routing.RoutingTable;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Priority;
 import org.elasticsearch.common.component.AbstractLifecycleComponent;
@@ -235,7 +235,7 @@ public class InternalClusterService extends AbstractLifecycleComponent<ClusterSe
         }
         // call the post added notification on the same event thread
         try {
-            updateTasksExecutor.execute(new PrioritizedRunnable(Priority.HIGH) {
+            updateTasksExecutor.execute(new TimedPrioritizedRunnable(Priority.HIGH, "_add_listener_") {
                 @Override
                 public void run() {
                     NotifyTimeout notifyTimeout = new NotifyTimeout(listener, timeout);
@@ -272,7 +272,7 @@ public class InternalClusterService extends AbstractLifecycleComponent<ClusterSe
                         threadPool.generic().execute(new Runnable() {
                             @Override
                             public void run() {
-                                timeoutUpdateTask.onFailure(task.source, new ProcessClusterEventTimeoutException(timeoutUpdateTask.timeout(), task.source));
+                                timeoutUpdateTask.onFailure(task.source(), new ProcessClusterEventTimeoutException(timeoutUpdateTask.timeout(), task.source()));
                             }
                         });
                     }
@@ -291,19 +291,19 @@ public class InternalClusterService extends AbstractLifecycleComponent<ClusterSe
 
     @Override
     public List<PendingClusterTask> pendingTasks() {
-        long now = System.currentTimeMillis();
         PrioritizedEsThreadPoolExecutor.Pending[] pendings = updateTasksExecutor.getPending();
         List<PendingClusterTask> pendingClusterTasks = new ArrayList<>(pendings.length);
         for (PrioritizedEsThreadPoolExecutor.Pending pending : pendings) {
             final String source;
             final long timeInQueue;
-            if (pending.task instanceof UpdateTask) {
-                UpdateTask updateTask = (UpdateTask) pending.task;
-                source = updateTask.source;
-                timeInQueue = now - updateTask.addedAt;
+            if (pending.task instanceof TimedPrioritizedRunnable) {
+                TimedPrioritizedRunnable runnable = (TimedPrioritizedRunnable) pending.task;
+                source = runnable.source();
+                timeInQueue = runnable.timeSinceCreatedInMillis();
             } else {
+                assert false : "expected TimedPrioritizedRunnable got " + pending.task.getClass();
                 source = "unknown";
-                timeInQueue = -1;
+                timeInQueue = 0;
             }
 
             pendingClusterTasks.add(new PendingClusterTask(pending.insertionOrder, pending.priority, new StringText(source), timeInQueue, pending.executing));
@@ -311,15 +311,34 @@ public class InternalClusterService extends AbstractLifecycleComponent<ClusterSe
         return pendingClusterTasks;
     }
 
-    class UpdateTask extends PrioritizedRunnable {
+    static abstract class TimedPrioritizedRunnable extends PrioritizedRunnable {
+        private final long creationTime;
+        protected final String source;
 
-        public final String source;
-        public final ClusterStateUpdateTask updateTask;
-        public final long addedAt = System.currentTimeMillis();
-
-        UpdateTask(String source, Priority priority, ClusterStateUpdateTask updateTask) {
+        protected TimedPrioritizedRunnable(Priority priority, String source) {
             super(priority);
             this.source = source;
+            this.creationTime = System.currentTimeMillis();
+        }
+
+        public long timeSinceCreatedInMillis() {
+            // max with 0 to make sure we always return a non negative number
+            // even if time shifts.
+            return Math.max(0, System.currentTimeMillis() - creationTime);
+        }
+
+        public String source() {
+            return source;
+        }
+    }
+
+    class UpdateTask extends TimedPrioritizedRunnable {
+
+        public final ClusterStateUpdateTask updateTask;
+
+
+        UpdateTask(String source, Priority priority, ClusterStateUpdateTask updateTask) {
+            super(priority, source);
             this.updateTask = updateTask;
         }
 
diff --git a/src/main/java/org/elasticsearch/cluster/service/PendingClusterTask.java b/src/main/java/org/elasticsearch/cluster/service/PendingClusterTask.java
index d9a1f9fc134..d53dcb32584 100644
--- a/src/main/java/org/elasticsearch/cluster/service/PendingClusterTask.java
+++ b/src/main/java/org/elasticsearch/cluster/service/PendingClusterTask.java
@@ -19,7 +19,6 @@
 
 package org.elasticsearch.cluster.service;
 
-import org.elasticsearch.Version;
 import org.elasticsearch.common.Priority;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
@@ -43,6 +42,8 @@ public class PendingClusterTask implements Streamable {
     }
 
     public PendingClusterTask(long insertOrder, Priority priority, Text source, long timeInQueue, boolean executing) {
+        assert timeInQueue >= 0 : "got a negative timeInQueue [" + timeInQueue + "]";
+        assert insertOrder >= 0 : "got a negative insertOrder [" + insertOrder + "]";
         this.insertOrder = insertOrder;
         this.priority = priority;
         this.source = source;