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[GitHub] drcrallen commented on a change in pull request #5492: Native parallel batch indexing without shuffle


drcrallen commented on a change in pull request #5492: Native parallel batch indexing without shuffle
URL: https://github.com/apache/incubator-druid/pull/5492#discussion_r201779862
 
 

 ##########
 File path: indexing-service/src/main/java/io/druid/indexing/common/task/TaskMonitor.java
 ##########
 @@ -0,0 +1,502 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets 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 io.druid.indexing.common.task;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.SettableFuture;
+import io.druid.client.indexing.IndexingServiceClient;
+import io.druid.client.indexing.TaskStatusResponse;
+import io.druid.indexer.TaskState;
+import io.druid.indexer.TaskStatusPlus;
+import io.druid.indexing.common.task.ParallelIndexSupervisorTask.Status;
+import io.druid.java.util.common.ISE;
+import io.druid.java.util.common.concurrent.Execs;
+import io.druid.java.util.common.logger.Logger;
+
+import javax.annotation.Nullable;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map.Entry;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
+
+/**
+ * Responsible for submitting tasks, monitoring task statuses, resubmitting failed tasks, and returning the final task
+ * status.
+ */
+public class TaskMonitor<T extends Task>
+{
+  private static final Logger log = new Logger(TaskMonitor.class);
+
+  private final ScheduledExecutorService taskStatusChecker = Execs.scheduledSingleThreaded(("task-monitor-%d"));
+
+  /**
+   * A map of subTaskSpecId to {@link MonitorEntry}. This map stores the state of running {@link SubTaskSpec}s. This is
+   * read in {@link java.util.concurrent.Callable} executed by {@link #taskStatusChecker} and updated in {@link #submit}
+   * and {@link #retry}. This can also be read by calling {@link #getRunningTaskMonitorEntory},
+   * {@link #getRunningTaskIds}, and {@link #getRunningSubTaskSpecs}.
+   */
+  private final ConcurrentMap<String, MonitorEntry> runningTasks = new ConcurrentHashMap<>();
+
+  /**
+   * A map of subTaskSpecId to {@link TaskHistory}. This map stores the history of complete {@link SubTaskSpec}s
+   * whether their final state is succeeded or failed. This is updated in {@link MonitorEntry#setLastStatus} which is
+   * called by the {@link java.util.concurrent.Callable} executed by {@link #taskStatusChecker} and can be
+   * read by outside of this class.
+   */
+  private final ConcurrentMap<String, TaskHistory<T>> taskHistories = new ConcurrentHashMap<>();
+
+  // lock for updating numRunningTasks, numSucceededTasks, and numFailedTasks
+  private final Object taskCountLock = new Object();
+
+  // overlord client
+  private final IndexingServiceClient indexingServiceClient;
+  private final int maxRetry;
+  private final int expectedNumSucceededTasks;
+
+  private int numRunningTasks;
+  private int numSucceededTasks;
+  private int numFailedTasks;
+
+  private volatile boolean running = false;
+
+  TaskMonitor(IndexingServiceClient indexingServiceClient, int maxRetry, int expectedNumSucceededTasks)
+  {
+    this.indexingServiceClient = Preconditions.checkNotNull(indexingServiceClient, "indexingServiceClient");
+    this.maxRetry = maxRetry;
+    this.expectedNumSucceededTasks = expectedNumSucceededTasks;
+
+    log.info("TaskMonitor is initialized with expectedNumSucceededTasks[%d]", expectedNumSucceededTasks);
+  }
+
+  public void start(long taskStatusCheckingPeriod)
+  {
+    running = true;
+    log.info("Starting taskMonitor");
+    // NOTE: This polling can be improved to event-driven pushing by registering TaskRunnerListener to TaskRunner.
+    // That listener should be able to send the events reported to TaskRunner to this TaskMonitor.
+    taskStatusChecker.scheduleAtFixedRate(
+        () -> {
+          try {
+            final Iterator<Entry<String, MonitorEntry>> iterator = runningTasks.entrySet().iterator();
 
 Review comment:
   Any reason not to use the fluent style here? would `runningTasks.forEachEntry(...)` work? 

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