/**
 * 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.hadoop.yarn.server.resourcemanager.scheduler.fair;

import org.apache.hadoop.yarn.api.records.ApplicationAttemptId;
import org.apache.hadoop.yarn.conf.YarnConfiguration;
import org.apache.hadoop.yarn.server.resourcemanager.MockRM;
import org.apache.hadoop.yarn.server.resourcemanager.rmnode.RMNode;
import org.apache.hadoop.yarn.server.resourcemanager.scheduler.event.NodeUpdateSchedulerEvent;

import org.junit.After;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertTrue;
import org.junit.Before;
import org.junit.Test;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;

/**
 * Test class to verify identification of app starvation
 */
public class TestFSAppStarvation extends FairSchedulerTestBase {

  private static final File ALLOC_FILE = new File(TEST_DIR, "test-QUEUES");

  // Node Capacity = NODE_CAPACITY_MULTIPLE * (1 GB or 1 vcore)
  private static final int NODE_CAPACITY_MULTIPLE = 4;
  private static final String[] QUEUES =
      {"no-preemption", "minshare", "fairshare.child", "drf.child"};

  private FairSchedulerWithMockPreemption.MockPreemptionThread preemptionThread;

  @Before
  public void setup() {
    createConfiguration();
    conf.set(YarnConfiguration.RM_SCHEDULER,
        FairSchedulerWithMockPreemption.class.getCanonicalName());
    conf.set(FairSchedulerConfiguration.ALLOCATION_FILE,
        ALLOC_FILE.getAbsolutePath());
    conf.setBoolean(FairSchedulerConfiguration.PREEMPTION, true);
    conf.setFloat(FairSchedulerConfiguration.PREEMPTION_THRESHOLD, 0f);
  }

  @After
  public void teardown() {
    ALLOC_FILE.delete();
    conf = null;
    if (resourceManager != null) {
      resourceManager.stop();
      resourceManager = null;
    }
  }

  /*
   * Test to verify application starvation is computed only when preemption
   * is enabled.
   */
  @Test
  public void testPreemptionDisabled() throws Exception {
    conf.setBoolean(FairSchedulerConfiguration.PREEMPTION, false);

    setupClusterAndSubmitJobs();

    assertNull("Found starved apps even when preemption is turned off",
        scheduler.getContext().getStarvedApps());
  }

  /*
   * Test to verify application starvation is computed correctly when
   * preemption is turned on.
   */
  @Test
  public void testPreemptionEnabled() throws Exception {
    setupClusterAndSubmitJobs();

    assertNotNull("FSContext does not have an FSStarvedApps instance",
        scheduler.getContext().getStarvedApps());
    assertEquals("Expecting 3 starved applications, one each for the "
            + "minshare and fairshare queues",
        3, preemptionThread.uniqueAppsAdded());

    // Verify the apps get added again on a subsequent update
    scheduler.update();
    Thread.yield();

    verifyLeafQueueStarvation();
    assertTrue("Each app is marked as starved exactly once",
        preemptionThread.totalAppsAdded() > preemptionThread.uniqueAppsAdded());
  }

  /*
   * Test to verify app starvation is computed only when the cluster
   * utilization threshold is over the preemption threshold.
   */
  @Test
  public void testClusterUtilizationThreshold() throws Exception {
    // Set preemption threshold to 1.1, so the utilization is always lower
    conf.setFloat(FairSchedulerConfiguration.PREEMPTION_THRESHOLD, 1.1f);

    setupClusterAndSubmitJobs();

    assertNotNull("FSContext does not have an FSStarvedApps instance",
        scheduler.getContext().getStarvedApps());
    assertEquals("Found starved apps when preemption threshold is over 100%", 0,
        preemptionThread.totalAppsAdded());
  }

  private void verifyLeafQueueStarvation() {
    for (String q : QUEUES) {
      if (!q.equals("no-preemption")) {
        boolean isStarved =
            scheduler.getQueueManager().getLeafQueue(q, false).isStarved();
        assertTrue(isStarved);
      }
    }
  }

  private void setupClusterAndSubmitJobs() throws Exception {
    setupStarvedCluster();
    submitAppsToEachLeafQueue();
    sendEnoughNodeUpdatesToAssignFully();

    // Sleep to hit the preemption timeouts
    Thread.sleep(10);

    // Scheduler update to populate starved apps
    scheduler.update();

    // Wait for apps to be processed by MockPreemptionThread
    Thread.yield();
  }

  /**
   * Setup the cluster for starvation testing:
   * 1. Create FS allocation file
   * 2. Create and start MockRM
   * 3. Add two nodes to the cluster
   * 4. Submit an app that uses up all resources on the cluster
   */
  private void setupStarvedCluster() throws IOException {
    PrintWriter out = new PrintWriter(new FileWriter(ALLOC_FILE));
    out.println("<?xml version=\"1.0\"?>");
    out.println("<allocations>");

    // Default queue
    out.println("<queue name=\"default\">");
    out.println("</queue>");

    // Queue with preemption disabled
    out.println("<queue name=\"no-preemption\">");
    out.println("<fairSharePreemptionThreshold>0" +
        "</fairSharePreemptionThreshold>");
    out.println("</queue>");

    // Queue with minshare preemption enabled
    out.println("<queue name=\"minshare\">");
    out.println("<fairSharePreemptionThreshold>0" +
        "</fairSharePreemptionThreshold>");
    out.println("<minSharePreemptionTimeout>0" +
        "</minSharePreemptionTimeout>");
    out.println("<minResources>2048mb,2vcores</minResources>");
    out.println("</queue>");

    // FAIR queue with fairshare preemption enabled
    out.println("<queue name=\"fairshare\">");
    out.println("<fairSharePreemptionThreshold>1" +
        "</fairSharePreemptionThreshold>");
    out.println("<fairSharePreemptionTimeout>0" +
        "</fairSharePreemptionTimeout>");
    out.println("<schedulingPolicy>fair</schedulingPolicy>");
    addChildQueue(out);
    out.println("</queue>");

    // DRF queue with fairshare preemption enabled
    out.println("<queue name=\"drf\">");
    out.println("<fairSharePreemptionThreshold>1" +
        "</fairSharePreemptionThreshold>");
    out.println("<fairSharePreemptionTimeout>0" +
        "</fairSharePreemptionTimeout>");
    out.println("<schedulingPolicy>drf</schedulingPolicy>");
    addChildQueue(out);
    out.println("</queue>");

    out.println("</allocations>");
    out.close();

    assertTrue("Allocation file does not exist, not running the test",
        ALLOC_FILE.exists());

    resourceManager = new MockRM(conf);
    resourceManager.start();
    scheduler = (FairScheduler) resourceManager.getResourceScheduler();
    preemptionThread = (FairSchedulerWithMockPreemption.MockPreemptionThread)
        scheduler.preemptionThread;

    // Create and add two nodes to the cluster
    addNode(NODE_CAPACITY_MULTIPLE * 1024, NODE_CAPACITY_MULTIPLE);
    addNode(NODE_CAPACITY_MULTIPLE * 1024, NODE_CAPACITY_MULTIPLE);

    // Create an app that takes up all the resources on the cluster
    ApplicationAttemptId app
        = createSchedulingRequest(1024, 1, "root.default", "default", 8);

    scheduler.update();
    sendEnoughNodeUpdatesToAssignFully();

    assertEquals(8, scheduler.getSchedulerApp(app).getLiveContainers().size());
  }

  private void addChildQueue(PrintWriter out) {
    // Child queue under fairshare with same settings
    out.println("<queue name=\"child\">");
    out.println("<fairSharePreemptionThreshold>1" +
        "</fairSharePreemptionThreshold>");
    out.println("<fairSharePreemptionTimeout>0" +
        "</fairSharePreemptionTimeout>");
    out.println("</queue>");
  }

  private void submitAppsToEachLeafQueue() {
    for (String queue : QUEUES) {
      createSchedulingRequest(1024, 1, "root." + queue, "user", 1);
    }
    scheduler.update();
  }

  private void sendEnoughNodeUpdatesToAssignFully() {
    for (RMNode node : rmNodes) {
      NodeUpdateSchedulerEvent nodeUpdateSchedulerEvent =
          new NodeUpdateSchedulerEvent(node);
      for (int i = 0; i < NODE_CAPACITY_MULTIPLE; i++) {
        scheduler.handle(nodeUpdateSchedulerEvent);
      }
    }
  }
}