TwillController.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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.apache.twill.api;

import com.google.common.util.concurrent.ListenableFuture;
import org.apache.twill.api.logging.LogHandler;
import org.apache.twill.discovery.Discoverable;
import org.apache.twill.discovery.ServiceDiscovered;

/**
 * For controlling a running application.
 */
public interface TwillController extends ServiceController {

  /**
   * Adds a {@link LogHandler} for receiving application log.
   * @param handler The handler to add.
   */
  void addLogHandler(LogHandler handler);

  /**
   * Discovers the set of {@link Discoverable} endpoints that provides service for the given service name.
   * @param serviceName Name of the service to discovery.
   * @return A {@link org.apache.twill.discovery.ServiceDiscovered} object representing the result.
   */
  ServiceDiscovered discoverService(String serviceName);


  /**
   * Changes the number of running instances of a given runnable.
   *
   * @param runnable The name of the runnable.
   * @param newCount Number of instances for the given runnable.
   * @return A {@link ListenableFuture} that will be completed when the number running instances has been
   *         successfully changed. The future will carry the new count as the result. If there is any error
   *         while changing instances, it'll be reflected in the future.
   */
  ListenableFuture<Integer> changeInstances(String runnable, int newCount);

  /**
   * Get a snapshot of the resources used by the application, broken down by each runnable.
   *
   * @return A {@link ResourceReport} containing information about resources used by the application.
   */
  ResourceReport getResourceReport();
}