api/src/main/java/org/apache/apex/api/plugin/DAGSetupPlugin.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.apex.api.plugin;

import java.util.Collection;

import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;

import com.datatorrent.api.Attribute;
import com.datatorrent.api.DAG;

/**
 * DAGSetupPlugin allows user provided code to run at various stages
 * during DAG preparation. Currently following stages are supported
 *
 * <ul>
 *   <li>Before dag is populated</li>
 *   <li>After dag is populated</li>
 *   <li>Before dag is configured</li>
 *   <li>After dag is configured</li>
 *   <li>Before dag is validated</li>
 *   <li>After dag is validated</li>
 * </ul>
 */
@InterfaceStability.Evolving
public interface DAGSetupPlugin extends Plugin<DAGSetupPlugin.DAGSetupPluginContext>
{

  /**
   * This method is called before platform adds operators and streams in the DAG. i.e this method
   * will get called just before {@link com.datatorrent.api.StreamingApplication#populateDAG(DAG, Configuration)}
   *
   * For Application specified using property and json file format, this method will get called
   * before platform adds operators and streams in the DAG as per specification in the file.
   */
  void prePopulateDAG();

  /**
   * This method is called after platform adds operators and streams in the DAG. i.e this method
   * will get called just after {@link com.datatorrent.api.StreamingApplication#populateDAG(DAG, Configuration)}
   * in case application is specified in java.
   *
   * For Application specified using property and json file format, this method will get called
   * after platform has added operators and streams in the DAG as per specification in the file.
   */
  void postPopulateDAG();

  /**
   * This is method is called before DAG is configured, i.e operator and application
   * properties/attributes are injected from configuration files.
   */
  void preConfigureDAG();

  /**
   * This is method is called after DAG is configured, i.e operator and application
   * properties/attributes are injected from configuration files.
   */
  void postConfigureDAG();

  /**
   * This method is called just before dag is validated before final job submission.
   */
  void preValidateDAG();

  /**
   * This method is called after dag is validated. If plugin makes in incompatible changes
   * to the DAG at this stage, then application may get launched incorrectly or application
   * launch may fail.
   */
  void postValidateDAG();

  class DAGSetupPluginContext implements PluginContext
  {
    private final DAG dag;
    private final Configuration conf;

    public DAGSetupPluginContext(DAG dag, Configuration conf)
    {
      this.dag = dag;
      this.conf = conf;
    }

    public DAG getDAG()
    {
      return dag;
    }

    public Configuration getConfiguration()
    {
      return conf;
    }

    @Override
    public Attribute.AttributeMap getAttributes()
    {
      throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public <T> T getValue(Attribute<T> key)
    {
      throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public void setCounters(Object counters)
    {
      throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public void sendMetrics(Collection<String> metricNames)
    {
      throw new UnsupportedOperationException("Not supported yet.");
    }
  }
}