[Transform] Check alias during update (#124825)

When the Transform System Index has been reindexed and aliased, we
should check the Transform Update index against the alias when updating
the Transform Config.

docs/changelog/124825.yaml

@@ -0,0 +1,5 @@
+pr: 124825
+summary: Check alias during update
+area: Transform
+type: bug
+issues: []

x-pack/plugin/transform/src/internalClusterTest/java/org/elasticsearch/xpack/transform/integration/TransformOldTransformsIT.java

@@ -16,6 +16,8 @@ import org.elasticsearch.common.ValidationException;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.core.Strings;
 import org.elasticsearch.core.TimeValue;
+import org.elasticsearch.index.reindex.ReindexAction;
+import org.elasticsearch.index.reindex.ReindexRequest;
 import org.elasticsearch.xcontent.XContentBuilder;
 import org.elasticsearch.xcontent.XContentFactory;
 import org.elasticsearch.xcontent.XContentType;
@@ -25,12 +27,16 @@ import org.elasticsearch.xpack.core.transform.TransformConfigVersion;
 import org.elasticsearch.xpack.core.transform.TransformDeprecations;
 import org.elasticsearch.xpack.core.transform.TransformField;
 import org.elasticsearch.xpack.core.transform.action.GetTransformAction;
+import org.elasticsearch.xpack.core.transform.action.PutTransformAction;
 import org.elasticsearch.xpack.core.transform.action.StartTransformAction;
 import org.elasticsearch.xpack.core.transform.action.StopTransformAction;
 import org.elasticsearch.xpack.core.transform.action.UpdateTransformAction;
+import org.elasticsearch.xpack.core.transform.transforms.DestConfig;
+import org.elasticsearch.xpack.core.transform.transforms.SourceConfig;
 import org.elasticsearch.xpack.core.transform.transforms.TransformConfig;
 import org.elasticsearch.xpack.core.transform.transforms.TransformConfigUpdate;
 import org.elasticsearch.xpack.core.transform.transforms.persistence.TransformInternalIndexConstants;
+import org.elasticsearch.xpack.core.transform.transforms.pivot.PivotConfigTests;
 import org.elasticsearch.xpack.core.transform.utils.TransformConfigVersionUtils;
 import org.elasticsearch.xpack.transform.TransformSingleNodeTestCase;
 import org.elasticsearch.xpack.transform.persistence.TransformInternalIndex;
@@ -253,4 +259,65 @@ public class TransformOldTransformsIT extends TransformSingleNodeTestCase {
         assertMaxPageSearchSizeInSettings(transformId, expectedMaxPageSearchSize);
     }
 
+    public void testMigratedTransformIndex() {
+        // create transform
+        var sourceIndex = "source-index";
+        createSourceIndex(sourceIndex);
+        var transformId = "transform-migrated-system-index";
+
+        var sourceConfig = new SourceConfig(sourceIndex);
+        var destConfig = new DestConfig("some-dest-index", null, null);
+        var config = new TransformConfig(
+            transformId,
+            sourceConfig,
+            destConfig,
+            null,
+            null,
+            null,
+            PivotConfigTests.randomPivotConfig(),
+            null,
+            null,
+            null,
+            null,
+            null,
+            null,
+            null
+        );
+        var putTransform = new PutTransformAction.Request(config, true, TimeValue.THIRTY_SECONDS);
+        assertTrue(client().execute(PutTransformAction.INSTANCE, putTransform).actionGet().isAcknowledged());
+
+        // simulate migration by reindexing and aliasing
+        var newSystemIndex = TransformInternalIndexConstants.LATEST_INDEX_NAME + "-reindexed";
+        var reindexRequest = new ReindexRequest();
+        reindexRequest.setSourceIndices(TransformInternalIndexConstants.LATEST_INDEX_NAME);
+        reindexRequest.setDestIndex(newSystemIndex);
+        reindexRequest.setRefresh(true);
+        client().execute(ReindexAction.INSTANCE, reindexRequest).actionGet();
+
+        var aliasesRequest = admin().indices().prepareAliases(TimeValue.THIRTY_SECONDS, TimeValue.THIRTY_SECONDS);
+        aliasesRequest.removeIndex(TransformInternalIndexConstants.LATEST_INDEX_NAME);
+        aliasesRequest.addAlias(newSystemIndex, TransformInternalIndexConstants.LATEST_INDEX_NAME);
+        aliasesRequest.execute().actionGet();
+
+        // update should succeed
+        var updateConfig = new TransformConfigUpdate(
+            sourceConfig,
+            new DestConfig("some-new-dest-index", null, null),
+            null,
+            null,
+            null,
+            null,
+            null,
+            null
+        );
+        var updateRequest = new UpdateTransformAction.Request(updateConfig, transformId, true, TimeValue.THIRTY_SECONDS);
+        client().execute(UpdateTransformAction.INSTANCE, updateRequest).actionGet();
+
+        // verify update succeeded
+        var getTransformRequest = new GetTransformAction.Request(transformId);
+        var getTransformResponse = client().execute(GetTransformAction.INSTANCE, getTransformRequest).actionGet();
+        var transformConfig = getTransformResponse.getTransformConfigurations().get(0);
+        assertThat(transformConfig.getDestination().getIndex(), equalTo("some-new-dest-index"));
+    }
+
 }

x-pack/plugin/transform/src/internalClusterTest/java/org/elasticsearch/xpack/transform/persistence/TransformConfigManagerTests.java

@@ -78,7 +78,8 @@ public class TransformConfigManagerTests extends TransformSingleNodeTestCase {
 
     @Before
     public void createComponents() {
-        clusterService = mock(ClusterService.class);
+        clusterService = mock();
+        when(clusterService.state()).thenReturn(ClusterState.EMPTY_STATE);
         transformConfigManager = new IndexBasedTransformConfigManager(
             clusterService,
             TestIndexNameExpressionResolver.newInstance(),

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

@@ -252,7 +252,7 @@ public class TransformUpdater {
             long lastCheckpoint = currentState.v1().getTransformState().getCheckpoint();
 
             // if: the state is stored on the latest index, it does not need an update
-            if (currentState.v2().getIndex().equals(TransformInternalIndexConstants.LATEST_INDEX_VERSIONED_NAME)) {
+            if (transformConfigManager.isLatestTransformIndex(currentState.v2().getIndex())) {
                 listener.onResponse(lastCheckpoint);
                 return;
             }
@@ -283,8 +283,7 @@ public class TransformUpdater {
         ActionListener<Boolean> listener
     ) {
         transformConfigManager.getTransformCheckpointForUpdate(transformId, lastCheckpoint, ActionListener.wrap(checkpointAndVersion -> {
-            if (checkpointAndVersion == null
-                || checkpointAndVersion.v2().getIndex().equals(TransformInternalIndexConstants.LATEST_INDEX_VERSIONED_NAME)) {
+            if (checkpointAndVersion == null || transformConfigManager.isLatestTransformIndex(checkpointAndVersion.v2().getIndex())) {
                 listener.onResponse(true);
                 return;
             }

x-pack/plugin/transform/src/main/java/org/elasticsearch/xpack/transform/persistence/IndexBasedTransformConfigManager.java

@@ -170,7 +170,7 @@ public class IndexBasedTransformConfigManager implements TransformConfigManager
             listener.onFailure(conflictStatusException("Cannot update Transform while the Transform feature is upgrading."));
             return;
         }
-        if (seqNoPrimaryTermAndIndex.getIndex().equals(TransformInternalIndexConstants.LATEST_INDEX_NAME)) {
+        if (isLatestTransformIndex(seqNoPrimaryTermAndIndex.getIndex())) {
             // update the config in the same, current index using optimistic concurrency control
             putTransformConfiguration(transformConfig, DocWriteRequest.OpType.INDEX, seqNoPrimaryTermAndIndex, listener);
         } else {
@@ -180,6 +180,21 @@ public class IndexBasedTransformConfigManager implements TransformConfigManager
         }
     }
 
+    @Override
+    public boolean isLatestTransformIndex(String indexName) {
+        if (TransformInternalIndexConstants.LATEST_INDEX_NAME.equals(indexName)) {
+            return true;
+        }
+
+        // in some cases, the System Index gets reindexed and LATEST_INDEX_NAME is now an alias pointing to that reindexed index
+        // this mostly likely happens after the SystemIndexMigrator ran
+        // we need to check if the LATEST_INDEX_NAME is now an alias and points to the indexName
+        var metadata = clusterService.state().projectState().metadata();
+        var indicesForAlias = metadata.aliasedIndices(TransformInternalIndexConstants.LATEST_INDEX_NAME);
+        var index = metadata.index(indexName);
+        return index != null && indicesForAlias.contains(index.getIndex());
+    }
+
     @Override
     public void deleteOldTransformConfigurations(String transformId, ActionListener<Boolean> listener) {
         if (isUpgrading()) {
@@ -697,7 +712,7 @@ public class IndexBasedTransformConfigManager implements TransformConfigManager
                 // could have been called, see gh#80073
                 indexRequest.opType(DocWriteRequest.OpType.INDEX);
                 // if on the latest index use optimistic concurrency control in addition
-                if (seqNoPrimaryTermAndIndex.getIndex().equals(TransformInternalIndexConstants.LATEST_INDEX_NAME)) {
+                if (isLatestTransformIndex(seqNoPrimaryTermAndIndex.getIndex())) {
                     indexRequest.setIfSeqNo(seqNoPrimaryTermAndIndex.getSeqNo())
                         .setIfPrimaryTerm(seqNoPrimaryTermAndIndex.getPrimaryTerm());
                 }

x-pack/plugin/transform/src/main/java/org/elasticsearch/xpack/transform/persistence/TransformConfigManager.java

@@ -15,6 +15,7 @@ import org.elasticsearch.xpack.core.transform.TransformField;
 import org.elasticsearch.xpack.core.transform.transforms.TransformCheckpoint;
 import org.elasticsearch.xpack.core.transform.transforms.TransformConfig;
 import org.elasticsearch.xpack.core.transform.transforms.TransformStoredDoc;
+import org.elasticsearch.xpack.core.transform.transforms.persistence.TransformInternalIndexConstants;
 
 import java.util.Collection;
 import java.util.Collections;
@@ -206,4 +207,8 @@ public interface TransformConfigManager {
     void getTransformStoredDocs(Collection<String> transformIds, TimeValue timeout, ActionListener<List<TransformStoredDoc>> listener);
 
     void refresh(ActionListener<Boolean> listener);
+
+    default boolean isLatestTransformIndex(String indexName) {
+        return TransformInternalIndexConstants.LATEST_INDEX_NAME.equals(indexName);
+    }
 }