/**
    *
    * 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.
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  package org.apache.hadoop.hbase.regionserver;
  
  
  import static org.junit.Assert.assertTrue;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.CountDownLatch;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellScanner;
  import org.apache.hadoop.hbase.HBaseTestingUtility;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.Server;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.client.Durability;
  import org.apache.hadoop.hbase.client.Put;
  import org.apache.hadoop.hbase.regionserver.wal.FSHLog;
  import org.apache.hadoop.hbase.regionserver.wal.WALEdit;
  import org.apache.hadoop.hbase.testclassification.MediumTests;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManagerTestHelper;
  import org.apache.hadoop.hbase.util.Threads;
  import org.apache.hadoop.hbase.wal.WAL;
  import org.apache.hadoop.hbase.wal.WALKey;
  import org.apache.hadoop.hbase.wal.WALProvider.Writer;
  import org.junit.After;
  import org.junit.Before;
  import org.junit.Rule;
  import org.junit.Test;
  import org.junit.experimental.categories.Category;
  import org.junit.rules.TestName;
  import org.mockito.Mockito;
  
  /**
   * Testing for lock up of WAL subsystem.
   * Copied from TestHRegion.
   */
  @Category({MediumTests.class})
  public class TestWALLockup {
    private static final Log LOG = LogFactory.getLog(TestWALLockup.class);
    @Rule public TestName name = new TestName();
  
    private static final String COLUMN_FAMILY = "MyCF";
    private static final byte [] COLUMN_FAMILY_BYTES = Bytes.toBytes(COLUMN_FAMILY);
  
    HRegion region = null;
    // Do not run unit tests in parallel (? Why not?  It don't work?  Why not?  St.Ack)
    private static HBaseTestingUtility TEST_UTIL;
    private static Configuration CONF ;
    private String dir;
  
    // Test names
    protected TableName tableName;
  
    @Before
    public void setup() throws IOException {
      TEST_UTIL = HBaseTestingUtility.createLocalHTU();
      CONF = TEST_UTIL.getConfiguration();
      // Disable block cache.
      CONF.setFloat(HConstants.HFILE_BLOCK_CACHE_SIZE_KEY, 0f);
      dir = TEST_UTIL.getDataTestDir("TestHRegion").toString();
      tableName = TableName.valueOf(name.getMethodName());
    }
  
    @After
    public void tearDown() throws Exception {
      EnvironmentEdgeManagerTestHelper.reset();
      LOG.info("Cleaning test directory: " + TEST_UTIL.getDataTestDir());
      TEST_UTIL.cleanupTestDir();
    }
  
    String getName() {
      return name.getMethodName();
   }
 
   /**
    * Reproduce locking up that happens when we get an inopportune sync during setup for
    * zigzaglatch wait. See HBASE-14317. If below is broken, we will see this test timeout because
    * it is locked up.
    * <p>First I need to set up some mocks for Server and RegionServerServices. I also need to
    * set up a dodgy WAL that will throw an exception when we go to append to it.
    */
   @Test (timeout=30000)
   public void testLockupWhenSyncInMiddleOfZigZagSetup() throws IOException {
     // A WAL that we can have throw exceptions when a flag is set.
     class DodgyFSLog extends FSHLog {
       // Set this when want the WAL to start throwing exceptions.
       volatile boolean throwException = false;
 
       // Latch to hold up processing until after another operation has had time to run.
       CountDownLatch latch = new CountDownLatch(1);
 
       public DodgyFSLog(FileSystem fs, Path root, String logDir, Configuration conf)
       throws IOException {
         super(fs, root, logDir, conf);
       }
 
       @Override
       protected void afterCreatingZigZagLatch() {
         // If throwException set, then append will throw an exception causing the WAL to be
         // rolled. We'll come in here. Hold up processing until a sync can get in before
         // the zigzag has time to complete its setup and get its own sync in. This is what causes
         // the lock up we've seen in production.
         if (throwException) {
           try {
             LOG.info("LATCHED");
             this.latch.await();
           } catch (InterruptedException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
           }
         }
       }
 
       @Override
       protected void beforeWaitOnSafePoint() {
         if (throwException) {
           LOG.info("COUNTDOWN");
           // Don't countdown latch until someone waiting on it otherwise, the above
           // afterCreatingZigZagLatch will get to the latch and no one will ever free it and we'll
           // be stuck; test won't go down
           while (this.latch.getCount() <= 0) Threads.sleep(1);
           this.latch.countDown();
         }
       }
 
       @Override
       protected Writer createWriterInstance(Path path) throws IOException {
         final Writer w = super.createWriterInstance(path);
         return new Writer() {
           @Override
           public void close() throws IOException {
             w.close();
           }
 
           @Override
           public void sync() throws IOException {
             if (throwException) {
               throw new IOException("FAKE! Failed to replace a bad datanode...SYNC");
             }
             w.sync();
           }
 
           @Override
           public void append(Entry entry) throws IOException {
             if (throwException) {
               throw new IOException("FAKE! Failed to replace a bad datanode...APPEND");
             }
             w.append(entry);
           }
 
           @Override
           public long getLength() throws IOException {
             return w.getLength();
           }
         };
       }
     }
 
     // Mocked up server and regionserver services. Needed below.
     Server server = Mockito.mock(Server.class);
     Mockito.when(server.getConfiguration()).thenReturn(CONF);
     Mockito.when(server.isStopped()).thenReturn(false);
     Mockito.when(server.isAborted()).thenReturn(false);
     RegionServerServices services = Mockito.mock(RegionServerServices.class);
 
     // OK. Now I have my mocked up Server & RegionServerServices and dodgy WAL, go ahead with test.
     FileSystem fs = FileSystem.get(CONF);
     Path rootDir = new Path(dir + getName());
     DodgyFSLog dodgyWAL = new DodgyFSLog(fs, rootDir, getName(), CONF);
     Path originalWAL = dodgyWAL.getCurrentFileName();
     // I need a log roller running.
     LogRoller logRoller = new LogRoller(server, services);
     logRoller.addWAL(dodgyWAL);
     // There is no 'stop' once a logRoller is running.. it just dies.
     logRoller.start();
     // Now get a region and start adding in edits.
     HTableDescriptor htd = new HTableDescriptor(TableName.META_TABLE_NAME);
     final HRegion region = initHRegion(tableName, null, null, dodgyWAL);
     byte [] bytes = Bytes.toBytes(getName());
     try {
       // First get something into memstore. Make a Put and then pull the Cell out of it. Will
       // manage append and sync carefully in below to manufacture hang. We keep adding same
       // edit. WAL subsystem doesn't care.
       Put put = new Put(bytes);
       put.addColumn(COLUMN_FAMILY_BYTES, Bytes.toBytes("1"), bytes);
       WALKey key = new WALKey(region.getRegionInfo().getEncodedNameAsBytes(), htd.getTableName());
       WALEdit edit = new WALEdit();
       List<Cell> cells = new ArrayList<Cell>();
       for (CellScanner cs = put.cellScanner(); cs.advance();) {
         edit.add(cs.current());
         cells.add(cs.current());
       }
       // Put something in memstore and out in the WAL. Do a big number of appends so we push
       // out other side of the ringbuffer. If small numbers, stuff doesn't make it to WAL
       for (int i = 0; i < 1000; i++) {
         dodgyWAL.append(htd, region.getRegionInfo(), key, edit, region.getSequenceId(), true,
           cells);
       }
       // Set it so we start throwing exceptions.
       dodgyWAL.throwException = true;
       // This append provokes a WAL roll.
       dodgyWAL.append(htd, region.getRegionInfo(), key, edit, region.getSequenceId(), true, cells);
       boolean exception = false;
       try {
         dodgyWAL.sync();
       } catch (Exception e) {
         exception = true;
       }
       assertTrue("Did not get sync exception", exception);
 
       // Get a memstore flush going too so we have same hung profile as up in the issue over
       // in HBASE-14317. Flush hangs trying to get sequenceid because the ringbuffer is held up
       // by the zigzaglatch waiting on syncs to come home.
       Thread t = new Thread ("flusher") {
         public void run() {
           try {
             region.flush(false);
           } catch (IOException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
           }
         };
       };
       t.setDaemon(true);
       t.start();
       // Wait till it gets into flushing. It will get stuck on getSequenceId. Then proceed.
       while (!region.writestate.flushing) Threads.sleep(1);
       // Now assert I got a new WAL file put in place even though loads of errors above.
       assertTrue(originalWAL != dodgyWAL.getCurrentFileName());
       // Can I append to it?
       dodgyWAL.throwException = false;
       region.put(put);
     } finally {
       // To stop logRoller, its server has to say it is stopped.
       Mockito.when(server.isStopped()).thenReturn(true);
       if (logRoller != null) logRoller.interrupt();
       if (region != null) region.close();
       if (dodgyWAL != null) dodgyWAL.close();
     }
   }
 
   /**
    * @return A region on which you must call
    *         {@link HBaseTestingUtility#closeRegionAndWAL(HRegion)} when done.
    */
   public HRegion initHRegion(TableName tableName, byte[] startKey, byte[] stopKey, WAL wal)
   throws IOException {
     return TEST_UTIL.createLocalHRegion(tableName.getName(), startKey, stopKey,
       getName(), CONF, false, Durability.SYNC_WAL,
       wal, COLUMN_FAMILY_BYTES);
   }
 }