[GitHub] taegeonum commented on a change in pull request #126: [NEMO-224] Simple StreamingScheduler

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taegeonum commented on a change in pull request #126: [NEMO-224] Simple StreamingScheduler
URL: https://github.com/apache/incubator-nemo/pull/126#discussion_r226884809
 
 

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 File path: runtime/master/src/main/java/org/apache/nemo/runtime/master/scheduler/StreamingScheduler.java
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 @@ -0,0 +1,134 @@
+/*
+ * Copyright (C) 2018 Seoul National University
+ *
+ * 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 org.apache.nemo.runtime.master.scheduler;
+
+import com.google.common.collect.Lists;
+import org.apache.nemo.common.ir.Readable;
+import org.apache.nemo.runtime.common.RuntimeIdManager;
+import org.apache.nemo.runtime.common.plan.PhysicalPlan;
+import org.apache.nemo.runtime.common.plan.Stage;
+import org.apache.nemo.runtime.common.plan.StageEdge;
+import org.apache.nemo.runtime.common.plan.Task;
+import org.apache.nemo.runtime.common.state.TaskState;
+import org.apache.nemo.runtime.master.*;
+import org.apache.nemo.runtime.master.resource.ExecutorRepresenter;
+import org.apache.reef.annotations.audience.DriverSide;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.NotThreadSafe;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+/**
+ * A simple scheduler for streaming workloads.
+ * - Keeps track of new executors
+ * - Schedules all tasks in a reverse topological order.
+ * - Crashes the system upon any other events (should be fixed in the future)
+ * - Never stops running.
+ */
+@DriverSide
+@NotThreadSafe
+public final class StreamingScheduler implements Scheduler {
+  private static final Logger LOG = LoggerFactory.getLogger(StreamingScheduler.class.getName());
+
+  private final TaskDispatcher taskDispatcher;
+  private final PendingTaskCollectionPointer pendingTaskCollectionPointer;
+  private final ExecutorRegistry executorRegistry;
+  private final PlanStateManager planStateManager;
+
+  StreamingScheduler(final TaskDispatcher taskDispatcher,
+                     final PendingTaskCollectionPointer pendingTaskCollectionPointer,
+                     final ExecutorRegistry executorRegistry,
+                     final PlanStateManager planStateManager) {
+    this.taskDispatcher = taskDispatcher;
+    this.pendingTaskCollectionPointer = pendingTaskCollectionPointer;
+    this.executorRegistry = executorRegistry;
+    this.planStateManager = planStateManager;
+  }
+
+  @Override
+  public void schedulePlan(final PhysicalPlan submittedPhysicalPlan,
+                           final int maxScheduleAttempt) {
+    // Housekeeping stuff
+    taskDispatcher.run();
+    planStateManager.updatePlan(submittedPhysicalPlan, maxScheduleAttempt);
+    planStateManager.storeJSON("submitted");
+
+    // Prepare tasks
+    final List<Stage> reverseTopoStages = Lists.reverse(submittedPhysicalPlan.getStageDAG().getTopologicalSort());
+    final List<Task> reverseTopoTasks = reverseTopoStages.stream().flatMap(stageToSchedule -> {
+      // Helper variables for this stage
+      final List<StageEdge> stageIncomingEdges =
+        submittedPhysicalPlan.getStageDAG().getIncomingEdgesOf(stageToSchedule.getId());
+      final List<StageEdge> stageOutgoingEdges =
+        submittedPhysicalPlan.getStageDAG().getOutgoingEdgesOf(stageToSchedule.getId());
+      final List<Map<String, Readable>> vertexIdToReadables = stageToSchedule.getVertexIdToReadables();
+      final List<String> taskIdsToSchedule = planStateManager.getTaskAttemptsToSchedule(stageToSchedule.getId());
+
+      // Create tasks of this stage
+      return taskIdsToSchedule.stream().map(taskId -> new Task(
+        submittedPhysicalPlan.getPlanId(),
+        taskId,
+        stageToSchedule.getExecutionProperties(),
+        stageToSchedule.getSerializedIRDAG(),
+        stageIncomingEdges,
+        stageOutgoingEdges,
+        vertexIdToReadables.get(RuntimeIdManager.getIndexFromTaskId(taskId))));
+    }).collect(Collectors.toList());
+
+    // Schedule everything at once
+    pendingTaskCollectionPointer.setToOverwrite(reverseTopoTasks);
+  }
+
+  @Override
+  public void updatePlan(final PhysicalPlan newPhysicalPlan) {
+    throw new UnsupportedOperationException();
+  }
+
+  public void onTaskStateReportFromExecutor(final String executorId,
 
 Review comment:
   When does this method is called? This naming is confusing to me because I thought it is called whenever the task status is changed. (e.g., task is started, created, finished, failed...). Maybe we need to change this name to onTaskFinishedOrFailed? 

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