TaskStateCollectorService.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 gobblin.runtime;

import com.google.common.base.Predicate;
import gobblin.metastore.FsStateStore;
import gobblin.metastore.StateStore;
import java.io.IOException;
import java.util.List;
import java.util.Properties;
import java.util.Queue;
import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;

import org.apache.hadoop.fs.Path;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Queues;
import com.google.common.eventbus.EventBus;
import com.google.common.util.concurrent.AbstractScheduledService;

import gobblin.configuration.ConfigurationKeys;
import gobblin.util.ParallelRunner;


/**
 * An {@link AbstractScheduledService} for collecting output {@link TaskState}s of completed {@link Task}s
 * stored in files, which get deleted once the {@link TaskState}s they store are successfully collected.
 * For each batch of {@link TaskState}s collected, it posts a {@link NewTaskCompletionEvent} to notify
 * parties that are interested in such events.
 *
 * @author Yinan Li
 */
public class TaskStateCollectorService extends AbstractScheduledService {

  private static final Logger LOGGER = LoggerFactory.getLogger(TaskStateCollectorService.class);

  private final JobState jobState;

  private final EventBus eventBus;

  // Number of ParallelRunner threads to be used for state serialization/deserialization
  private final int stateSerDeRunnerThreads;

  // Interval in seconds between two runs of the collector of output TaskStates
  private final int outputTaskStatesCollectorIntervalSeconds;

  private final StateStore<TaskState> taskStateStore;

  private final Path outputTaskStateDir;

  public TaskStateCollectorService(Properties jobProps, JobState jobState, EventBus eventBus,
      StateStore<TaskState> taskStateStore, Path outputTaskStateDir) {
    this.jobState = jobState;
    this.eventBus = eventBus;
    this.taskStateStore = taskStateStore;
    this.outputTaskStateDir = outputTaskStateDir;

    this.stateSerDeRunnerThreads = Integer.parseInt(jobProps.getProperty(ParallelRunner.PARALLEL_RUNNER_THREADS_KEY,
        Integer.toString(ParallelRunner.DEFAULT_PARALLEL_RUNNER_THREADS)));

    this.outputTaskStatesCollectorIntervalSeconds =
        Integer.parseInt(jobProps.getProperty(ConfigurationKeys.TASK_STATE_COLLECTOR_INTERVAL_SECONDS,
            Integer.toString(ConfigurationKeys.DEFAULT_TASK_STATE_COLLECTOR_INTERVAL_SECONDS)));
  }

  @Override
  protected void runOneIteration() throws Exception {
    collectOutputTaskStates();
  }

  @Override
  protected Scheduler scheduler() {
    return Scheduler.newFixedRateSchedule(this.outputTaskStatesCollectorIntervalSeconds,
        this.outputTaskStatesCollectorIntervalSeconds, TimeUnit.SECONDS);
  }

  @Override
  protected void startUp() throws Exception {
    LOGGER.info("Starting the " + TaskStateCollectorService.class.getSimpleName());
    super.startUp();
  }

  @Override
  protected void shutDown() throws Exception {
    LOGGER.info("Stopping the " + TaskStateCollectorService.class.getSimpleName());
    try {
      runOneIteration();
    } finally {
      super.shutDown();
    }
  }

  /**
   * Collect output {@link TaskState}s of tasks of the job launched.
   *
   * <p>
   *   This method collects all available output {@link TaskState} files at the time it is called. It
   *   uses a {@link ParallelRunner} to deserialize the {@link TaskState}s. Each {@link TaskState}
   *   file gets deleted after the {@link TaskState} it stores is successfully collected.
   * </p>
   *
   * @throws IOException if it fails to collect the output {@link TaskState}s
   */
  private void collectOutputTaskStates() throws IOException {
    List<String> taskStateNames = taskStateStore.getTableNames(outputTaskStateDir.getName(), new Predicate<String>() {
      @Override
      public boolean apply(String input) {
        return input.endsWith(AbstractJobLauncher.TASK_STATE_STORE_TABLE_SUFFIX)
        && !input.startsWith(FsStateStore.TMP_FILE_PREFIX);
      }});

    if (taskStateNames == null || taskStateNames.size() == 0) {
      LOGGER.warn("No output task state files found in " + this.outputTaskStateDir);
      return;
    }

    final Queue<TaskState> taskStateQueue = Queues.newConcurrentLinkedQueue();
    try (ParallelRunner stateSerDeRunner = new ParallelRunner(this.stateSerDeRunnerThreads, null)) {
      for (final String taskStateName : taskStateNames) {
        LOGGER.debug("Found output task state file " + taskStateName);
        // Deserialize the TaskState and delete the file
        stateSerDeRunner.submitCallable(new Callable<Void>() {
          @Override
          public Void call() throws Exception {
            TaskState taskState = taskStateStore.getAll(outputTaskStateDir.getName(), taskStateName).get(0);
            taskStateQueue.add(taskState);
            taskStateStore.delete(outputTaskStateDir.getName(), taskStateName);
            return null;
          }
        }, "Deserialize state for " + taskStateName);
      }
    } catch (IOException ioe) {
      LOGGER.warn("Could not read all task state files.");
    }

    LOGGER.info(String.format("Collected task state of %d completed tasks", taskStateQueue.size()));

    // Add the TaskStates of completed tasks to the JobState so when the control
    // returns to the launcher, it sees the TaskStates of all completed tasks.
    for (TaskState taskState : taskStateQueue) {
      taskState.setJobState(this.jobState);
      this.jobState.addTaskState(taskState);
    }

    // Notify the listeners for the completion of the tasks
    this.eventBus.post(new NewTaskCompletionEvent(ImmutableList.copyOf(taskStateQueue)));
  }
}