[7.x] Migrate aliased indices to data stream (#66176)

server/src/main/java/org/elasticsearch/cluster/metadata/ComposableIndexTemplate.java

@@ -112,6 +112,12 @@ public ComposableIndexTemplate(List<String> indexPatterns, @Nullable Template te
         this(indexPatterns, template, componentTemplates, priority, version, metadata, null, null);
     }
 
+    public ComposableIndexTemplate(List<String> indexPatterns, @Nullable Template template, @Nullable List<String> componentTemplates,
+        @Nullable Long priority, @Nullable Long version, @Nullable Map<String, Object> metadata,
+        @Nullable DataStreamTemplate dataStreamTemplate) {
+        this(indexPatterns, template, componentTemplates, priority, version, metadata, dataStreamTemplate, null);
+    }
+
     public ComposableIndexTemplate(List<String> indexPatterns, @Nullable Template template, @Nullable List<String> componentTemplates,
                                    @Nullable Long priority, @Nullable Long version, @Nullable Map<String, Object> metadata,
                                    @Nullable DataStreamTemplate dataStreamTemplate, @Nullable Boolean allowAutoCreate) {

server/src/main/java/org/elasticsearch/cluster/metadata/DataStream.java

@@ -71,7 +71,6 @@ public DataStream(String name, TimestampField timeStampField, List<Index> indice
         this.hidden = hidden;
         this.replicated = replicated;
         assert indices.size() > 0;
-        assert indices.get(indices.size() - 1).getName().equals(getDefaultBackingIndexName(name, generation));
     }
 
     public DataStream(String name, TimestampField timeStampField, List<Index> indices) {
@@ -94,6 +93,10 @@ public long getGeneration() {
         return generation;
     }
 
+    public Index getWriteIndex() {
+        return indices.get(indices.size() - 1);
+    }
+
     @Nullable
     public Map<String, Object> getMetadata() {
         return metadata;

server/src/main/java/org/elasticsearch/cluster/metadata/IndexAbstraction.java

@@ -31,7 +31,6 @@
 import java.util.Objects;
 import java.util.stream.Collectors;
 
-import static org.elasticsearch.cluster.metadata.DataStream.getDefaultBackingIndexName;
 import static org.elasticsearch.cluster.metadata.IndexMetadata.INDEX_HIDDEN_SETTING;
 import static org.elasticsearch.common.collect.List.copyOf;
 
@@ -309,7 +308,6 @@ public DataStream(org.elasticsearch.cluster.metadata.DataStream dataStream, List
             this.dataStream = dataStream;
             this.dataStreamIndices = copyOf(dataStreamIndices);
             this.writeIndex =  dataStreamIndices.get(dataStreamIndices.size() - 1);
-            assert writeIndex.getIndex().getName().equals(getDefaultBackingIndexName(dataStream.getName(), dataStream.getGeneration()));
         }
 
         @Override

server/src/main/java/org/elasticsearch/cluster/metadata/MetadataCreateDataStreamService.java

@@ -33,21 +33,24 @@
 import org.elasticsearch.cluster.ack.ClusterStateUpdateRequest;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.Priority;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.NamedXContentRegistry;
 import org.elasticsearch.common.xcontent.ObjectPath;
+import org.elasticsearch.index.Index;
 import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.mapper.MetadataFieldMapper;
 import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.threadpool.ThreadPool;
 
 import java.io.IOException;
-import java.util.Collections;
-import java.util.HashMap;
+import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Objects;
 import java.util.concurrent.atomic.AtomicReference;
+import java.util.stream.Collectors;
 
 public class MetadataCreateDataStreamService {
 
@@ -116,54 +119,81 @@ public CreateDataStreamClusterStateUpdateRequest(String name,
     static ClusterState createDataStream(MetadataCreateIndexService metadataCreateIndexService,
                                          ClusterState currentState,
                                          CreateDataStreamClusterStateUpdateRequest request) throws Exception {
+        return createDataStream(metadataCreateIndexService, currentState, request.name, org.elasticsearch.common.collect.List.of(), null);
+    }
+
+    /**
+     * Creates a data stream with the specified properties.
+     *
+     * @param metadataCreateIndexService Used if a new write index must be created
+     * @param currentState               Cluster state
+     * @param dataStreamName             Name of the data stream
+     * @param backingIndices             List of backing indices. May be empty
+     * @param writeIndex                 Write index for the data stream. If null, a new write index will be created.
+     * @return                           Cluster state containing the new data stream
+     */
+    static ClusterState createDataStream(MetadataCreateIndexService metadataCreateIndexService,
+                                         ClusterState currentState,
+                                         String dataStreamName,
+                                         List<IndexMetadata> backingIndices,
+                                         IndexMetadata writeIndex) throws Exception
+    {
         if (currentState.nodes().getMinNodeVersion().before(Version.V_7_9_0)) {
             throw new IllegalStateException("data streams require minimum node version of " + Version.V_7_9_0);
         }
-
-        if (currentState.metadata().dataStreams().containsKey(request.name)) {
-            throw new ResourceAlreadyExistsException("data_stream [" + request.name + "] already exists");
+        if (writeIndex == null) {
+            Objects.requireNonNull(metadataCreateIndexService);
+        }
+        Objects.requireNonNull(currentState);
+        Objects.requireNonNull(backingIndices);
+        if (currentState.metadata().dataStreams().containsKey(dataStreamName)) {
+            throw new ResourceAlreadyExistsException("data_stream [" + dataStreamName + "] already exists");
         }
 
-        MetadataCreateIndexService.validateIndexOrAliasName(request.name,
+        MetadataCreateIndexService.validateIndexOrAliasName(dataStreamName,
             (s1, s2) -> new IllegalArgumentException("data_stream [" + s1 + "] " + s2));
 
-        if (request.name.toLowerCase(Locale.ROOT).equals(request.name) == false) {
-            throw new IllegalArgumentException("data_stream [" + request.name + "] must be lowercase");
+        if (dataStreamName.toLowerCase(Locale.ROOT).equals(dataStreamName) == false) {
+            throw new IllegalArgumentException("data_stream [" + dataStreamName + "] must be lowercase");
         }
-        if (request.name.startsWith(DataStream.BACKING_INDEX_PREFIX)) {
-            throw new IllegalArgumentException("data_stream [" + request.name + "] must not start with '"
+        if (dataStreamName.startsWith(DataStream.BACKING_INDEX_PREFIX)) {
+            throw new IllegalArgumentException("data_stream [" + dataStreamName + "] must not start with '"
                 + DataStream.BACKING_INDEX_PREFIX + "'");
         }
 
-        ComposableIndexTemplate template = lookupTemplateForDataStream(request.name, currentState.metadata());
-
-        String firstBackingIndexName = DataStream.getDefaultBackingIndexName(request.name, 1);
-        CreateIndexClusterStateUpdateRequest createIndexRequest =
-            new CreateIndexClusterStateUpdateRequest("initialize_data_stream", firstBackingIndexName, firstBackingIndexName)
-                .dataStreamName(request.name)
-                .settings(Settings.builder().put("index.hidden", true).build());
-        try {
-            currentState = metadataCreateIndexService.applyCreateIndexRequest(currentState, createIndexRequest, false);
-        } catch (ResourceAlreadyExistsException e) {
-            // Rethrow as ElasticsearchStatusException, so that bulk transport action doesn't ignore it during
-            // auto index/data stream creation.
-            // (otherwise bulk execution fails later, because data stream will also not have been created)
-            throw new ElasticsearchStatusException("data stream could not be created because backing index [{}] already exists",
-                RestStatus.BAD_REQUEST, e, firstBackingIndexName);
+        ComposableIndexTemplate template = lookupTemplateForDataStream(dataStreamName, currentState.metadata());
+
+        if (writeIndex == null) {
+            String firstBackingIndexName = DataStream.getDefaultBackingIndexName(dataStreamName, 1);
+            CreateIndexClusterStateUpdateRequest createIndexRequest =
+                new CreateIndexClusterStateUpdateRequest("initialize_data_stream", firstBackingIndexName, firstBackingIndexName)
+                    .dataStreamName(dataStreamName)
+                    .settings(Settings.builder().put("index.hidden", true).build());
+            try {
+                currentState = metadataCreateIndexService.applyCreateIndexRequest(currentState, createIndexRequest, false);
+            } catch (ResourceAlreadyExistsException e) {
+                // Rethrow as ElasticsearchStatusException, so that bulk transport action doesn't ignore it during
+                // auto index/data stream creation.
+                // (otherwise bulk execution fails later, because data stream will also not have been created)
+                throw new ElasticsearchStatusException("data stream could not be created because backing index [{}] already exists",
+                    RestStatus.BAD_REQUEST, e, firstBackingIndexName);
+            }
+            writeIndex = currentState.metadata().index(firstBackingIndexName);
         }
-        IndexMetadata firstBackingIndex = currentState.metadata().index(firstBackingIndexName);
-        assert firstBackingIndex != null;
-        assert firstBackingIndex.mapping() != null : "no mapping found for backing index [" + firstBackingIndexName + "]";
+        assert writeIndex != null;
+        assert writeIndex.mapping() != null : "no mapping found for backing index [" + writeIndex.getIndex().getName() + "]";
 
         String fieldName = template.getDataStreamTemplate().getTimestampField();
         DataStream.TimestampField timestampField = new DataStream.TimestampField(fieldName);
+        List<Index> dsBackingIndices = backingIndices.stream().map(IndexMetadata::getIndex).collect(Collectors.toList());
+        dsBackingIndices.add(writeIndex.getIndex());
         boolean hidden = template.getDataStreamTemplate().isHidden();
-        DataStream newDataStream =
-            new DataStream(request.name, timestampField,
-                Collections.singletonList(firstBackingIndex.getIndex()), 1L,
-                template.metadata() != null ? Collections.unmodifiableMap(new HashMap<>(template.metadata())) : null, hidden, false);
+        DataStream newDataStream = new DataStream(dataStreamName, timestampField, dsBackingIndices, 1L,
+            template.metadata() != null ? org.elasticsearch.common.collect.Map.copyOf(template.metadata()) : null, hidden, false);
         Metadata.Builder builder = Metadata.builder(currentState.metadata()).put(newDataStream);
-        logger.info("adding data stream [{}]", request.name);
+        logger.info("adding data stream [{}] with write index [{}] and backing indices [{}]", dataStreamName,
+            writeIndex.getIndex().getName(),
+            Strings.arrayToCommaDelimitedString(backingIndices.stream().map(i -> i.getIndex().getName()).toArray()));
         return ClusterState.builder(currentState).metadata(builder).build();
     }