heron/api/src/java/org/apache/heron/streamlet/Context.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.heron.streamlet;

import java.io.Serializable;
import java.util.Map;
import java.util.function.Supplier;

import org.apache.heron.api.state.State;

/**
 * Context is the information available at runtime for operators like transform.
 * It contains basic things like config, runtime information like task,
 * the stream that it is operating on, ProcessState, etc.
 */
public interface Context {
  /**
   * Fetches the task id of the current instance of the operator
   * @return the task id.
   */
  int getTaskId();

  /**
   * Fetches the config of the computation
   * @return config
   */
  Map<String, Object> getConfig();

  /**
   * The stream name that we are operating on
   * @return the stream name that we are operating on
   */
  String getStreamName();

  /**
   * The partition number that we are operating on
   * @return the partition number
   */
  int getStreamPartition();

  /**
   * Register a metric function. This function will be called
   * by the system every collectionInterval seconds and the resulting value
   * will be collected
   */
  <T> void registerMetric(String metricName, int collectionInterval,
                      Supplier<T> metricFn);

  /**
   * The state where components can store any of their local state
   * @return The state interface where users can store their local state
   */
  State<Serializable, Serializable> getState();
}