content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.master;
  
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertTrue;
  
  import alluxio.conf.Configuration;
  import alluxio.conf.PropertyKey;
  import alluxio.resource.LockResource;
  import alluxio.util.CommonUtils;
  
  import com.google.common.util.concurrent.SettableFuture;
  import org.junit.Assert;
  import org.junit.Rule;
  import org.junit.Test;
  import org.junit.rules.ExpectedException;
  
  import java.util.Collection;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.TimeoutException;
  import java.util.concurrent.locks.Lock;
  import java.util.concurrent.locks.ReentrantLock;
  
  /**
   * Tests {@link StateLockManager} functionality.
   */
  public class StateLockManagerTest {
  
    @Rule
    public ExpectedException mExpected = ExpectedException.none();
  
    private void configureInterruptCycle(boolean enabled) {
      configureInterruptCycle(enabled, 100);
    }
  
    private void configureInterruptCycle(boolean enabled, long intervalMs) {
      Configuration.set(PropertyKey.MASTER_BACKUP_STATE_LOCK_INTERRUPT_CYCLE_ENABLED, enabled);
      Configuration.set(PropertyKey.MASTER_BACKUP_STATE_LOCK_INTERRUPT_CYCLE_INTERVAL,
          intervalMs);
    }
  
    @Test
    public void testGraceMode_Timeout() throws Throwable {
      configureInterruptCycle(false);
      // The state-lock instance.
      StateLockManager stateLockManager = new StateLockManager();
      // Start a thread that owns the state-lock in shared mode.
      StateLockingThread sharedHolderThread = new StateLockingThread(stateLockManager, false);
      sharedHolderThread.start();
      sharedHolderThread.waitUntilStateLockAcquired();
      // Expect timeout when the lock is held in shared mode.
      mExpected.expect(TimeoutException.class);
      stateLockManager
          .lockExclusive(new StateLockOptions(GraceMode.TIMEOUT, 10, 0, 100));
      // Exit the shared holder.
      sharedHolderThread.unlockExit();
      sharedHolderThread.join();
      // Create an exclusive owner of the state-lock.
      StateLockingThread exclusiveHolderThread = new StateLockingThread(stateLockManager, true);
      exclusiveHolderThread.start();
      exclusiveHolderThread.waitUntilStateLockAcquired();
      // Expect timeout when the lock is held in exclusive mode.
      mExpected.expect(TimeoutException.class);
      stateLockManager
          .lockExclusive(new StateLockOptions(GraceMode.TIMEOUT, 10, 0, 100));
      // Exit the exclusive holder.
      exclusiveHolderThread.unlockExit();
      exclusiveHolderThread.join();
      // Now the lock can be acquired within the grace-cycle.
      try (LockResource lr = stateLockManager
          .lockExclusive(new StateLockOptions(GraceMode.TIMEOUT, 10, 0, 100))) {
        // Acquired within the grace-cycle with no active holder.
      }
    }
  
    @Test
    public void testGraceMode_Forced() throws Throwable {
      // Enable interrupt-cycle with 100ms interval.
      configureInterruptCycle(true, 100);
      // The state-lock instance.
      StateLockManager stateLockManager = new StateLockManager();
      // Start a thread that owns the state-lock in shared mode.
      StateLockingThread sharedHolderThread = new StateLockingThread(stateLockManager, false);
      sharedHolderThread.start();
      sharedHolderThread.waitUntilStateLockAcquired();
      // Take the state-lock exclusively with GUARANTEED grace mode.
      try (LockResource lr = stateLockManager
          .lockExclusive(new StateLockOptions(GraceMode.FORCED, 10, 0, 100))) {
        // Holder should have been interrupted.
        Assert.assertTrue(sharedHolderThread.lockInterrupted());
        sharedHolderThread.join();
        // Spawn a new thread that waits on the lock.
        StateLockingThread sharedWaiterThread = new StateLockingThread(stateLockManager, false);
        sharedWaiterThread.start();
        // Wait until it's interrupted by the cycle too.
        CommonUtils.waitFor("waiter interrupted", () -> sharedWaiterThread.lockInterrupted());
        sharedWaiterThread.join();
      }
    }
  
    @Test
    public void testExclusiveOnlyMode() throws Throwable {
      // Configure exclusive-only duration to cover the entire test execution.
      final long exclusiveOnlyDurationMs = 30 * 1000;
      Configuration.set(PropertyKey.MASTER_BACKUP_STATE_LOCK_EXCLUSIVE_DURATION,
          exclusiveOnlyDurationMs);
  
      // The state-lock instance.
      StateLockManager stateLockManager = new StateLockManager();
      // Simulate masters-started event to initiate the exclusive-only phase.
      stateLockManager.mastersStartedCallback();
  
      for (int i = 0; i < 10; i++) {
        StateLockingThread sharedHolderThread = new StateLockingThread(stateLockManager, false);
        sharedHolderThread.start();
        // Shared lockers are expected to fail.
        mExpected.expect(IllegalStateException.class);
        sharedHolderThread.waitUntilStateLockAcquired();
      }
  
      // Exclusive locking should be allowed.
      StateLockingThread exclusiveHolderThread = new StateLockingThread(stateLockManager, true);
      exclusiveHolderThread.start();
      // State lock should be acquired.
      exclusiveHolderThread.waitUntilStateLockAcquired();
      // Signal exit and wait for the exclusive locker.
      exclusiveHolderThread.unlockExit();
      exclusiveHolderThread.join();
    }
  
    @Test
    // TODO(jiacheng): run this test before committing
    public void testGetStateLockSharedWaitersAndHolders() throws Throwable {
      final StateLockManager stateLockManager = new StateLockManager();
  
      assertEquals(0, stateLockManager.getSharedWaitersAndHolders().size());
  
      for (int i = 1; i < 10; i++) {
        StateLockingThread sharedHolderThread = new StateLockingThread(stateLockManager, false);
        sharedHolderThread.start();
        sharedHolderThread.waitUntilStateLockAcquired();
        final Collection<String> sharedWaitersAndHolders =
            stateLockManager.getSharedWaitersAndHolders();
        assertEquals(i, sharedWaitersAndHolders.size());
        assertTrue(sharedWaitersAndHolders.contains(
            sharedHolderThread.getName()));
      }
    }
  
    /**
     * Test thread that:
     *  1- locks on state-lock with requested mode shared/exclusive.
     *  2- fires that state-lock is acquired.
     *  3- sleeps on internal lock before exiting, while holding the state-lock.
     *  4- releases the state-lock right before exiting.
     */
    class StateLockingThread extends Thread {
      private StateLockManager mStateLockManager;
      private boolean mExclusive;
      private Lock mExitLock = new ReentrantLock();
      private SettableFuture<Void> mStateLockAcquired;
      private boolean mInterrupted = false;
  
      /**
       * Creates a state-locking test thread.
       *
       * @param stateLockManager state lock manager
       * @param exclusive whether to acquire the state-lock exclusives
       */
      public StateLockingThread(StateLockManager stateLockManager, boolean exclusive) {
        mStateLockManager = stateLockManager;
        mExclusive = exclusive;
        mStateLockAcquired = SettableFuture.create();
        mExitLock.lock();
      }
  
      @Override
      public void run() {
        LockResource lr = null;
        try {
          if (mExclusive) {
            lr = mStateLockManager.lockExclusive(StateLockOptions.defaults());
          } else {
            lr = mStateLockManager.lockShared();
          }
          mStateLockAcquired.set(null);
  
          mExitLock.lockInterruptibly();
        } catch (Exception e) {
          if (e instanceof InterruptedException) {
            mInterrupted = true;
          }
          mStateLockAcquired.setException(e);
        } finally {
          if (lr != null) {
            lr.close();
          }
        }
      }
  
      /**
       * Allows thread to exit after acquiring the state-lock.
       */
      public void unlockExit() {
        mExitLock.unlock();
      }
  
      /**
       * Holds the caller until this thread acquires the state-lock.
       *
       * @throws Exception that is received while acquiring the state-lock
       */
      public void waitUntilStateLockAcquired() throws Throwable {
        try {
          mStateLockAcquired.get();
        } catch (ExecutionException e) {
          if (e.getCause() != null) {
            throw e.getCause();
          } else {
            throw e;
          }
        }
      }
  
      /**
       * @return {@code true} if this thread is interrupted around locks
       */
      public boolean lockInterrupted() {
        return mInterrupted;
      }
    }
  }
  