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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;

import org.elasticsearch.cluster.block.ClusterBlock;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.cluster.routing.OperationRouting;
import org.elasticsearch.cluster.service.PendingClusterTask;
import org.elasticsearch.common.Nullable;
import org.elasticsearch.common.component.LifecycleComponent;
import org.elasticsearch.common.unit.TimeValue;
import org.elasticsearch.tasks.TaskManager;

import java.util.List;

/**
 * The cluster service allowing to both register for cluster state events ({@link ClusterStateListener})
 * and submit state update tasks ({@link ClusterStateUpdateTask}.
 */
public interface ClusterService extends LifecycleComponent {

    /**
     * The local node.
     */
    DiscoveryNode localNode();

    /**
     * The current state.
     */
    ClusterState state();

    /**
     * Adds an initial block to be set on the first cluster state created.
     */
    void addInitialStateBlock(ClusterBlock block) throws IllegalStateException;

    /**
     * Remove an initial block to be set on the first cluster state created.
     */
    void removeInitialStateBlock(ClusterBlock block) throws IllegalStateException;

    /**
     * The operation routing.
     */
    OperationRouting operationRouting();

    /**
     * Adds a priority listener for updated cluster states.
     */
    void addFirst(ClusterStateListener listener);

    /**
     * Adds last listener.
     */
    void addLast(ClusterStateListener listener);

    /**
     * Adds a listener for updated cluster states.
     */
    void add(ClusterStateListener listener);

    /**
     * Removes a listener for updated cluster states.
     */
    void remove(ClusterStateListener listener);

    /**
     * Add a listener for on/off local node master events
     */
    void add(LocalNodeMasterListener listener);

    /**
     * Remove the given listener for on/off local master events
     */
    void remove(LocalNodeMasterListener listener);

    /**
     * Adds a cluster state listener that will timeout after the provided timeout,
     * and is executed after the clusterstate has been successfully applied ie. is
     * in state {@link org.elasticsearch.cluster.ClusterState.ClusterStateStatus#APPLIED}
     * NOTE: a {@code null} timeout means that the listener will never be removed
     * automatically
     */
    void add(@Nullable TimeValue timeout, TimeoutClusterStateListener listener);

    /**
     * Submits a cluster state update task; submitted updates will be
     * batched across the same instance of executor. The exact batching
     * semantics depend on the underlying implementation but a rough
     * guideline is that if the update task is submitted while there
     * are pending update tasks for the same executor, these update
     * tasks will all be executed on the executor in a single batch
     *
     * @param source   the source of the cluster state update task
     * @param task     the state needed for the cluster state update task
     * @param config   the cluster state update task configuration
     * @param executor the cluster state update task executor; tasks
     *                 that share the same executor will be executed
     *                 batches on this executor
     * @param listener callback after the cluster state update task
     *                 completes
     * @param       the type of the cluster state update task state
     */
     void submitStateUpdateTask(final String source, final T task,
                                   final ClusterStateTaskConfig config,
                                   final ClusterStateTaskExecutor executor,
                                   final ClusterStateTaskListener listener);

    /**
     * Submits a cluster state update task; unlike {@link #submitStateUpdateTask(String, Object, ClusterStateTaskConfig, ClusterStateTaskExecutor, ClusterStateTaskListener)},
     * submitted updates will not be batched.
     *
     * @param source     the source of the cluster state update task
     * @param updateTask the full context for the cluster state update
     *                   task
     */
    void submitStateUpdateTask(final String source, final ClusterStateUpdateTask updateTask);

    /**
     * Returns the tasks that are pending.
     */
    List pendingTasks();

    /**
     * Returns the number of currently pending tasks.
     */
    int numberOfPendingTasks();

    /**
     * Returns the maximum wait time for tasks in the queue
     *
     * @return A zero time value if the queue is empty, otherwise the time value oldest task waiting in the queue
     */
    TimeValue getMaxTaskWaitTime();

    /**
     * Returns task manager created in the cluster service
     */
    TaskManager getTaskManager();
}