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/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.elasticsearch.cluster.metadata;

import org.elasticsearch.ElasticsearchException;
import org.elasticsearch.action.ActionListener;
import org.elasticsearch.action.admin.indices.alias.IndicesAliasesClusterStateUpdateRequest;
import org.elasticsearch.cluster.AckedClusterStateUpdateTask;
import org.elasticsearch.cluster.ClusterState;
import org.elasticsearch.cluster.ack.ClusterStateUpdateResponse;
import org.elasticsearch.cluster.metadata.AliasAction.NewAliasValidator;
import org.elasticsearch.cluster.service.ClusterService;
import org.elasticsearch.common.Priority;
import org.elasticsearch.common.Strings;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.xcontent.NamedXContentRegistry;
import org.elasticsearch.index.Index;
import org.elasticsearch.index.IndexNotFoundException;
import org.elasticsearch.index.IndexService;
import org.elasticsearch.index.mapper.MapperService;
import org.elasticsearch.indices.IndicesService;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.Function;

import static java.util.Collections.emptyList;
import static org.elasticsearch.indices.cluster.IndicesClusterStateService.AllocatedIndices.IndexRemovalReason.NO_LONGER_ASSIGNED;

/**
 * Service responsible for submitting add and remove aliases requests
 */
public class MetaDataIndexAliasesService {

    private final ClusterService clusterService;

    private final IndicesService indicesService;

    private final AliasValidator aliasValidator;

    private final MetaDataDeleteIndexService deleteIndexService;

    private final NamedXContentRegistry xContentRegistry;

    @Inject
    public MetaDataIndexAliasesService(ClusterService clusterService, IndicesService indicesService,
            AliasValidator aliasValidator, MetaDataDeleteIndexService deleteIndexService, NamedXContentRegistry xContentRegistry) {
        this.clusterService = clusterService;
        this.indicesService = indicesService;
        this.aliasValidator = aliasValidator;
        this.deleteIndexService = deleteIndexService;
        this.xContentRegistry = xContentRegistry;
    }

    public void indicesAliases(final IndicesAliasesClusterStateUpdateRequest request,
                               final ActionListener listener) {
        clusterService.submitStateUpdateTask("index-aliases",
            new AckedClusterStateUpdateTask(Priority.URGENT, request, listener) {
                @Override
                protected ClusterStateUpdateResponse newResponse(boolean acknowledged) {
                    return new ClusterStateUpdateResponse(acknowledged);
                }

                @Override
                public ClusterState execute(ClusterState currentState) {
                    return innerExecute(currentState, request.actions());
                }
            });
    }

    ClusterState innerExecute(ClusterState currentState, Iterable actions) {
        List indicesToClose = new ArrayList<>();
        Map indices = new HashMap<>();
        try {
            boolean changed = false;
            // Gather all the indexes that must be removed first so:
            // 1. We don't cause error when attempting to replace an index with a alias of the same name.
            // 2. We don't allow removal of aliases from indexes that we're just going to delete anyway. That'd be silly.
            Set indicesToDelete = new HashSet<>();
            for (AliasAction action : actions) {
                if (action.removeIndex()) {
                    IndexMetaData index = currentState.metaData().getIndices().get(action.getIndex());
                    if (index == null) {
                        throw new IndexNotFoundException(action.getIndex());
                    }
                    indicesToDelete.add(index.getIndex());
                    changed = true;
                }
            }
            // Remove the indexes if there are any to remove
            if (changed) {
                currentState = deleteIndexService.deleteIndices(currentState, indicesToDelete);
            }
            MetaData.Builder metadata = MetaData.builder(currentState.metaData());
            // Run the remaining alias actions
            for (AliasAction action : actions) {
                if (action.removeIndex()) {
                    // Handled above
                    continue;
                }
                IndexMetaData index = metadata.get(action.getIndex());
                if (index == null) {
                    throw new IndexNotFoundException(action.getIndex());
                }
                NewAliasValidator newAliasValidator = (alias, indexRouting, filter, writeIndex) -> {
                    /* It is important that we look up the index using the metadata builder we are modifying so we can remove an
                     * index and replace it with an alias. */
                    Function indexLookup = name -> metadata.get(name);
                    aliasValidator.validateAlias(alias, action.getIndex(), indexRouting, indexLookup);
                    if (Strings.hasLength(filter)) {
                        IndexService indexService = indices.get(index.getIndex().getName());
                        if (indexService == null) {
                            indexService = indicesService.indexService(index.getIndex());
                            if (indexService == null) {
                                // temporarily create the index and add mappings so we can parse the filter
                                try {
                                    indexService = indicesService.createIndex(index, emptyList());
                                    indicesToClose.add(index.getIndex());
                                } catch (IOException e) {
                                    throw new ElasticsearchException("Failed to create temporary index for parsing the alias", e);
                                }
                                indexService.mapperService().merge(index, MapperService.MergeReason.MAPPING_RECOVERY, false);
                            }
                            indices.put(action.getIndex(), indexService);
                        }
                        // the context is only used for validation so it's fine to pass fake values for the shard id and the current
                        // timestamp
                        aliasValidator.validateAliasFilter(alias, filter, indexService.newQueryShardContext(0, null, () -> 0L, null),
                                xContentRegistry);
                    }
                };
                changed |= action.apply(newAliasValidator, metadata, index);
            }

            if (changed) {
                ClusterState updatedState = ClusterState.builder(currentState).metaData(metadata).build();
                // even though changes happened, they resulted in 0 actual changes to metadata
                // i.e. remove and add the same alias to the same index
                if (!updatedState.metaData().equalsAliases(currentState.metaData())) {
                    return updatedState;
                }
            }
            return currentState;
        } finally {
            for (Index index : indicesToClose) {
                indicesService.removeIndex(index, NO_LONGER_ASSIGNED, "created for alias processing");
            }
        }
    }

}




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