diff --git a/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/exec/ControllerClient.java b/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/exec/ControllerClient.java
index b3675f0e047..afd1ece4dad 100644
--- a/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/exec/ControllerClient.java
+++ b/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/exec/ControllerClient.java
@@ -73,8 +73,12 @@ public interface ControllerClient extends AutoCloseable
   void postWorkerWarning(
       List<MSQErrorReport> MSQErrorReports
   ) throws IOException;
+
   List<String> getTaskList() throws IOException;
 
+  /**
+   * Close this client. Idempotent.
+   */
   @Override
   void close();
 }
diff --git a/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/exec/WorkerImpl.java b/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/exec/WorkerImpl.java
index 3f2ef39b5bf..e76169f7042 100644
--- a/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/exec/WorkerImpl.java
+++ b/extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/exec/WorkerImpl.java
@@ -498,20 +498,16 @@ public class WorkerImpl implements Worker
   @Override
   public void stopGracefully()
   {
-    log.info("Stopping gracefully for taskId [%s]", task.getId());
-    kernelManipulationQueue.add(
-        kernel -> {
-          // stopGracefully() is called when the containing process is terminated, or when the task is canceled.
-          throw new MSQException(CanceledFault.INSTANCE);
-        }
-    );
+    // stopGracefully() is called when the containing process is terminated, or when the task is canceled.
+    log.info("Worker task[%s] canceled.", task.getId());
+    doCancel();
   }
 
   @Override
   public void controllerFailed()
   {
-    controllerAlive = false;
-    stopGracefully();
+    log.info("Controller task[%s] for worker task[%s] failed. Canceling.", task.getControllerTaskId(), task.getId());
+    doCancel();
   }
 
   @Override
@@ -909,6 +905,31 @@ public class WorkerImpl implements Worker
     }
   }
 
+  /**
+   * Called by {@link #stopGracefully()} (task canceled, or containing process shut down) and
+   * {@link #controllerFailed()}.
+   */
+  private void doCancel()
+  {
+    // Set controllerAlive = false so we don't try to contact the controller after being canceled. If it canceled us,
+    // it doesn't need to know that we were canceled. If we were canceled by something else, the controller will
+    // detect this as part of its monitoring of workers.
+    controllerAlive = false;
+
+    // Close controller client to cancel any currently in-flight calls to the controller.
+    if (controllerClient != null) {
+      controllerClient.close();
+    }
+
+    // Clear the main loop event queue, then throw a CanceledFault into the loop to exit it promptly.
+    kernelManipulationQueue.clear();
+    kernelManipulationQueue.add(
+        kernel -> {
+          throw new MSQException(CanceledFault.INSTANCE);
+        }
+    );
+  }
+
   /**
    * Log (at DEBUG level) a string explaining the status of all work assigned to this worker.
    */