Avoiding a race condition where pending indices count is 0 at start of data stream reindex (elastic#123765) (elastic#123770)

Author: masseyke

x-pack/plugin/migrate/src/main/java/org/elasticsearch/xpack/migrate/action/GetMigrationReindexStatusTransportAction.java

@@ -145,7 +145,7 @@ private void reportStatus(
     }
 
     /*
-     * This method feches doc counts for all indices in inProgressIndices (and the indices they are being reindexed into). After
+     * This method fetches doc counts for all indices in inProgressIndices (and the indices they are being reindexed into). After
      * successfully fetching those, reportStatus is called.
      */
     private void fetchInProgressStatsAndReportStatus(

x-pack/plugin/migrate/src/main/java/org/elasticsearch/xpack/migrate/task/ReindexDataStreamPersistentTaskExecutor.java

@@ -88,7 +88,7 @@ protected ReindexDataStreamTask createTask(
             id,
             type,
             action,
-            "id=" + taskInProgress.getId(),
+            "Reindexing data stream " + taskInProgress.getParams().getSourceDataStream(),
             parentTaskId,
             headers
         );

x-pack/plugin/migrate/src/main/java/org/elasticsearch/xpack/migrate/task/ReindexDataStreamTask.java

@@ -55,6 +55,7 @@ public ReindexDataStreamTask(
         this.persistentTaskStartTime = persistentTaskStartTime;
         this.initialTotalIndices = initialTotalIndices;
         this.initialTotalIndicesToBeUpgraded = initialTotalIndicesToBeUpgraded;
+        this.pending.set(initialTotalIndicesToBeUpgraded);
         this.completeTask = new RunOnce(() -> {
             if (exception == null) {
                 markAsCompleted();