IRepacking.java

// Copyright 2016 Twitter. All rights reserved.
//
// Licensed 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 com.twitter.heron.spi.packing;

import java.util.Map;

import com.twitter.heron.api.generated.TopologyAPI;
import com.twitter.heron.classification.InterfaceAudience;
import com.twitter.heron.classification.InterfaceStability;
import com.twitter.heron.spi.common.Config;

/**
 * Packing algorithm for adding and/or removing component instances from an existing packing plan
 * Packing hints like number of containers may be passed through scheduler config.
 */
@InterfaceAudience.LimitedPrivate
@InterfaceStability.Unstable
public interface IRepacking extends AutoCloseable {

  /**
   * Initialize the packing algorithm with the static config and the associated topology
   * @param config topology config
   * @param topology topology to repack
   */
  void initialize(Config config, TopologyAPI.Topology topology);

  /**
   * Generates a new packing given an existing packing and component changes
   * Packing algorithm output generates instance id and container id.
   * @param currentPackingPlan Existing packing plan
   * @param componentChanges Map < componentName, new component parallelism >
   * that contains the parallelism for each component whose parallelism has changed.
   * @return PackingPlan describing the new packing plan.
   * @throws PackingException if the packing plan can not be generated
   */
  PackingPlan repack(PackingPlan currentPackingPlan,
                     Map<String, Integer> componentChanges) throws PackingException;

  /**
   * This is to for disposing or cleaning up any internal state.
   * Closes this stream and releases any system resources associated
   * with it. If the stream is already closed then invoking this
   * method has no effect.
   */
  void close();
}