[Transform] Shutdown the task immediately when force == true (#100203) (#100504)

Author: przemekwitek

docs/changelog/100203.yaml

@@ -0,0 +1,5 @@
+pr: 100203
+summary: Shutdown the task immediately when `force` == `true`
+area: Transform
+type: bug
+issues: []

x-pack/plugin/transform/src/main/java/org/elasticsearch/xpack/transform/action/TransportStopTransformAction.java

@@ -241,6 +241,20 @@ protected void taskOperation(
         }
 
         if (ids.contains(transformTask.getTransformId())) {
+            if (request.isForce()) {
+                // If force==true, we skip the additional step (setShouldStopAtCheckpoint) and move directly to shutting down the task.
+                // This way we ensure that the persistent task is removed ASAP (as opposed to being removed in one of the listeners).
+                try {
+                    // Here the task is deregistered in scheduler and marked as completed in persistent task service.
+                    transformTask.shutdown();
+                    // Here the indexer is aborted so that its thread finishes work ASAP.
+                    transformTask.onCancelled();
+                    listener.onResponse(new Response(true));
+                } catch (ElasticsearchException ex) {
+                    listener.onFailure(ex);
+                }
+                return;
+            }
             // move the call to the generic thread pool, so we do not block the network thread
             threadPool.generic().execute(() -> {
                 transformTask.setShouldStopAtCheckpoint(request.isWaitForCheckpoint(), ActionListener.wrap(r -> {