/**
 * 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.hbase.client;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertTrue;

import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.net.SocketTimeoutException;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.HBaseClassTestRule;
import org.apache.hadoop.hbase.HBaseTestingUtility;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.HRegionLocation;
import org.apache.hadoop.hbase.RegionLocations;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.Waiter;
import org.apache.hadoop.hbase.exceptions.ClientExceptionsUtil;
import org.apache.hadoop.hbase.exceptions.DeserializationException;
import org.apache.hadoop.hbase.exceptions.RegionMovedException;
import org.apache.hadoop.hbase.filter.Filter;
import org.apache.hadoop.hbase.filter.FilterBase;
import org.apache.hadoop.hbase.ipc.RpcClient;
import org.apache.hadoop.hbase.master.HMaster;
import org.apache.hadoop.hbase.regionserver.HRegion;
import org.apache.hadoop.hbase.regionserver.HRegionServer;
import org.apache.hadoop.hbase.regionserver.Region;
import org.apache.hadoop.hbase.regionserver.RegionServerStoppedException;
import org.apache.hadoop.hbase.testclassification.LargeTests;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.hadoop.hbase.util.JVMClusterUtil;
import org.apache.hadoop.hbase.util.ManualEnvironmentEdge;
import org.apache.hadoop.hbase.util.Threads;
import org.junit.After;
import org.junit.AfterClass;
import org.junit.Assert;
import org.junit.BeforeClass;
import org.junit.ClassRule;
import org.junit.Ignore;
import org.junit.Rule;
import org.junit.Test;
import org.junit.experimental.categories.Category;
import org.junit.rules.TestName;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.hbase.thirdparty.com.google.common.collect.Lists;
import org.apache.hbase.thirdparty.io.netty.util.ResourceLeakDetector;
import org.apache.hbase.thirdparty.io.netty.util.ResourceLeakDetector.Level;

/**
 * This class is for testing HBaseConnectionManager features
 */
@Category({LargeTests.class})
public class TestConnectionImplementation {

  @ClassRule
  public static final HBaseClassTestRule CLASS_RULE =
      HBaseClassTestRule.forClass(TestConnectionImplementation.class);

  private static final Logger LOG = LoggerFactory.getLogger(TestConnectionImplementation.class);
  private final static HBaseTestingUtility TEST_UTIL = new HBaseTestingUtility();
  private static final TableName TABLE_NAME =
      TableName.valueOf("test");
  private static final TableName TABLE_NAME1 =
      TableName.valueOf("test1");
  private static final TableName TABLE_NAME2 =
      TableName.valueOf("test2");
  private static final TableName TABLE_NAME3 =
      TableName.valueOf("test3");
  private static final byte[] FAM_NAM = Bytes.toBytes("f");
  private static final byte[] ROW = Bytes.toBytes("bbb");
  private static final byte[] ROW_X = Bytes.toBytes("xxx");
  private static final int RPC_RETRY = 5;

  @Rule
  public TestName name = new TestName();

  @BeforeClass
  public static void setUpBeforeClass() throws Exception {
    ResourceLeakDetector.setLevel(Level.PARANOID);
    TEST_UTIL.getConfiguration().setBoolean(HConstants.STATUS_PUBLISHED, true);
    // Up the handlers; this test needs more than usual.
    TEST_UTIL.getConfiguration().setInt(HConstants.REGION_SERVER_HIGH_PRIORITY_HANDLER_COUNT, 10);
    TEST_UTIL.getConfiguration().setInt(HConstants.HBASE_CLIENT_RETRIES_NUMBER, RPC_RETRY);
    TEST_UTIL.getConfiguration().setInt(HConstants.REGION_SERVER_HANDLER_COUNT, 3);
    TEST_UTIL.startMiniCluster(2);

  }

  @AfterClass
  public static void tearDownAfterClass() throws Exception {
    TEST_UTIL.shutdownMiniCluster();
  }

  @After
  public void tearDown() throws IOException {
    TEST_UTIL.getAdmin().balancerSwitch(true, true);
  }

  @Test
  public void testClusterConnection() throws IOException {
    ThreadPoolExecutor otherPool = new ThreadPoolExecutor(1, 1,
        5, TimeUnit.SECONDS,
        new SynchronousQueue<>(),
        Threads.newDaemonThreadFactory("test-hcm"));

    Connection con1 = ConnectionFactory.createConnection(TEST_UTIL.getConfiguration());
    Connection con2 = ConnectionFactory.createConnection(TEST_UTIL.getConfiguration(), otherPool);
    // make sure the internally created ExecutorService is the one passed
    assertTrue(otherPool == ((ConnectionImplementation) con2).getCurrentBatchPool());

    final TableName tableName = TableName.valueOf(name.getMethodName());
    TEST_UTIL.createTable(tableName, FAM_NAM).close();
    Table table = con1.getTable(tableName, otherPool);

    ExecutorService pool = null;

    if(table instanceof HTable) {
      HTable t = (HTable) table;
      // make sure passing a pool to the getTable does not trigger creation of an internal pool
      assertNull("Internal Thread pool should be null",
        ((ConnectionImplementation) con1).getCurrentBatchPool());
      // table should use the pool passed
      assertTrue(otherPool == t.getPool());
      t.close();

      t = (HTable) con2.getTable(tableName);
      // table should use the connectin's internal pool
      assertTrue(otherPool == t.getPool());
      t.close();

      t = (HTable) con2.getTable(tableName);
      // try other API too
      assertTrue(otherPool == t.getPool());
      t.close();

      t = (HTable) con2.getTable(tableName);
      // try other API too
      assertTrue(otherPool == t.getPool());
      t.close();

      t = (HTable) con1.getTable(tableName);
      pool = ((ConnectionImplementation) con1).getCurrentBatchPool();
      // make sure an internal pool was created
      assertNotNull("An internal Thread pool should have been created", pool);
      // and that the table is using it
      assertTrue(t.getPool() == pool);
      t.close();

      t = (HTable) con1.getTable(tableName);
      // still using the *same* internal pool
      assertTrue(t.getPool() == pool);
      t.close();
    } else {
      table.close();
    }

    con1.close();

    // if the pool was created on demand it should be closed upon connection close
    if(pool != null) {
      assertTrue(pool.isShutdown());
    }

    con2.close();
    // if the pool is passed, it is not closed
    assertFalse(otherPool.isShutdown());
    otherPool.shutdownNow();
  }

  /**
   * Naive test to check that Connection#getAdmin returns a properly constructed HBaseAdmin object
   * @throws IOException Unable to construct admin
   */
  @Test
  public void testAdminFactory() throws IOException {
    Connection con1 = ConnectionFactory.createConnection(TEST_UTIL.getConfiguration());
    Admin admin = con1.getAdmin();
    assertTrue(admin.getConnection() == con1);
    assertTrue(admin.getConfiguration() == TEST_UTIL.getConfiguration());
    con1.close();
  }

  // Fails too often!  Needs work.  HBASE-12558
  // May only fail on non-linux machines? E.g. macosx.
  @Ignore @Test (expected = RegionServerStoppedException.class)
  // Depends on mulitcast messaging facility that seems broken in hbase2
  // See  HBASE-19261 "ClusterStatusPublisher where Master could optionally broadcast notice of
  // dead servers is broke"
  public void testClusterStatus() throws Exception {
    final TableName tableName = TableName.valueOf(name.getMethodName());
    byte[] cf = "cf".getBytes();
    byte[] rk = "rk1".getBytes();

    JVMClusterUtil.RegionServerThread rs = TEST_UTIL.getHBaseCluster().startRegionServer();
    rs.waitForServerOnline();
    final ServerName sn = rs.getRegionServer().getServerName();

    Table t = TEST_UTIL.createTable(tableName, cf);
    TEST_UTIL.waitTableAvailable(tableName);
    TEST_UTIL.waitUntilNoRegionsInTransition();

    final ConnectionImplementation hci =  (ConnectionImplementation)TEST_UTIL.getConnection();
    try (RegionLocator l = TEST_UTIL.getConnection().getRegionLocator(tableName)) {
      while (l.getRegionLocation(rk).getPort() != sn.getPort()) {
        TEST_UTIL.getAdmin().move(l.getRegionLocation(rk).getRegionInfo().getEncodedNameAsBytes(),
          sn);
        TEST_UTIL.waitUntilNoRegionsInTransition();
        hci.clearRegionCache(tableName);
      }
      Assert.assertNotNull(hci.clusterStatusListener);
      TEST_UTIL.assertRegionOnServer(l.getRegionLocation(rk).getRegionInfo(), sn, 20000);
    }

    Put p1 = new Put(rk);
    p1.addColumn(cf, "qual".getBytes(), "val".getBytes());
    t.put(p1);

    rs.getRegionServer().abort("I'm dead");

    // We want the status to be updated. That's a least 10 second
    TEST_UTIL.waitFor(40000, 1000, true, new Waiter.Predicate<Exception>() {
      @Override
      public boolean evaluate() throws Exception {
        return TEST_UTIL.getHBaseCluster().getMaster().getServerManager().
            getDeadServers().isDeadServer(sn);
      }
    });

    TEST_UTIL.waitFor(40000, 1000, true, new Waiter.Predicate<Exception>() {
      @Override
      public boolean evaluate() throws Exception {
        return hci.clusterStatusListener.isDeadServer(sn);
      }
    });

    t.close();
    hci.getClient(sn);  // will throw an exception: RegionServerStoppedException
  }

  /**
   * Test that we can handle connection close: it will trigger a retry, but the calls will finish.
   */
  @Test
  public void testConnectionCloseAllowsInterrupt() throws Exception {
    testConnectionClose(true);
  }

  @Test
  public void testConnectionNotAllowsInterrupt() throws Exception {
    testConnectionClose(false);
  }

  private void testConnectionClose(boolean allowsInterrupt) throws Exception {
    TableName tableName = TableName.valueOf("HCM-testConnectionClose" + allowsInterrupt);
    TEST_UTIL.createTable(tableName, FAM_NAM).close();

    TEST_UTIL.getAdmin().balancerSwitch(false, true);

    Configuration c2 = new Configuration(TEST_UTIL.getConfiguration());
    // We want to work on a separate connection.
    c2.set(HConstants.HBASE_CLIENT_INSTANCE_ID, String.valueOf(-1));
    c2.setInt(HConstants.HBASE_CLIENT_RETRIES_NUMBER, 100); // retry a lot
    c2.setInt(HConstants.HBASE_CLIENT_PAUSE, 1); // don't wait between retries.
    c2.setInt(RpcClient.FAILED_SERVER_EXPIRY_KEY, 0); // Server do not really expire
    c2.setBoolean(RpcClient.SPECIFIC_WRITE_THREAD, allowsInterrupt);
    // to avoid the client to be stuck when do the Get
    c2.setInt(HConstants.HBASE_CLIENT_META_OPERATION_TIMEOUT, 10000);
    c2.setInt(HConstants.HBASE_CLIENT_OPERATION_TIMEOUT, 10000);
    c2.setInt(HConstants.HBASE_RPC_TIMEOUT_KEY, 5000);

    Connection connection = ConnectionFactory.createConnection(c2);
    final Table table = connection.getTable(tableName);

    Put put = new Put(ROW);
    put.addColumn(FAM_NAM, ROW, ROW);
    table.put(put);

    // 4 steps: ready=0; doGets=1; mustStop=2; stopped=3
    final AtomicInteger step = new AtomicInteger(0);

    final AtomicReference<Throwable> failed = new AtomicReference<>(null);
    Thread t = new Thread("testConnectionCloseThread") {
      @Override
      public void run() {
        int done = 0;
        try {
          step.set(1);
          while (step.get() == 1) {
            Get get = new Get(ROW);
            table.get(get);
            done++;
            if (done % 100 == 0)
              LOG.info("done=" + done);
            // without the sleep, will cause the exception for too many files in
            // org.apache.hadoop.hdfs.server.datanode.DataXceiver
            Thread.sleep(100);
          }
        } catch (Throwable t) {
          failed.set(t);
          LOG.error(t.toString(), t);
        }
        step.set(3);
      }
    };
    t.start();
    TEST_UTIL.waitFor(20000, new Waiter.Predicate<Exception>() {
      @Override
      public boolean evaluate() throws Exception {
        return step.get() == 1;
      }
    });

    ServerName sn;
    try(RegionLocator rl = connection.getRegionLocator(tableName)) {
      sn = rl.getRegionLocation(ROW).getServerName();
    }
    ConnectionImplementation conn =
        (ConnectionImplementation) connection;
    RpcClient rpcClient = conn.getRpcClient();

    LOG.info("Going to cancel connections. connection=" + conn.toString() + ", sn=" + sn);
    for (int i = 0; i < 500; i++) {
      rpcClient.cancelConnections(sn);
      Thread.sleep(50);
    }

    step.compareAndSet(1, 2);
    // The test may fail here if the thread doing the gets is stuck. The way to find
    //  out what's happening is to look for the thread named 'testConnectionCloseThread'
    TEST_UTIL.waitFor(40000, new Waiter.Predicate<Exception>() {
      @Override
      public boolean evaluate() throws Exception {
        return step.get() == 3;
      }
    });
    table.close();
    connection.close();
    Assert.assertTrue("Unexpected exception is " + failed.get(), failed.get() == null);
  }

  /**
   * Test that connection can become idle without breaking everything.
   */
  @Test
  public void testConnectionIdle() throws Exception {
    final TableName tableName = TableName.valueOf(name.getMethodName());
    TEST_UTIL.createTable(tableName, FAM_NAM).close();
    int idleTime =  20000;
    boolean previousBalance = TEST_UTIL.getAdmin().setBalancerRunning(false, true);

    Configuration c2 = new Configuration(TEST_UTIL.getConfiguration());
    // We want to work on a separate connection.
    c2.set(HConstants.HBASE_CLIENT_INSTANCE_ID, String.valueOf(-1));
    c2.setInt(HConstants.HBASE_CLIENT_RETRIES_NUMBER, 1); // Don't retry: retry = test failed
    c2.setInt(RpcClient.IDLE_TIME, idleTime);

    Connection connection = ConnectionFactory.createConnection(c2);
    final Table table = connection.getTable(tableName);

    Put put = new Put(ROW);
    put.addColumn(FAM_NAM, ROW, ROW);
    table.put(put);

    ManualEnvironmentEdge mee = new ManualEnvironmentEdge();
    mee.setValue(System.currentTimeMillis());
    EnvironmentEdgeManager.injectEdge(mee);
    LOG.info("first get");
    table.get(new Get(ROW));

    LOG.info("first get - changing the time & sleeping");
    mee.incValue(idleTime + 1000);
    Thread.sleep(1500); // we need to wait a little for the connection to be seen as idle.
                        // 1500 = sleep time in RpcClient#waitForWork + a margin

    LOG.info("second get - connection has been marked idle in the middle");
    // To check that the connection actually became idle would need to read some private
    //  fields of RpcClient.
    table.get(new Get(ROW));
    mee.incValue(idleTime + 1000);

    LOG.info("third get - connection is idle, but the reader doesn't know yet");
    // We're testing here a special case:
    //  time limit reached BUT connection not yet reclaimed AND a new call.
    //  in this situation, we don't close the connection, instead we use it immediately.
    // If we're very unlucky we can have a race condition in the test: the connection is already
    //  under closing when we do the get, so we have an exception, and we don't retry as the
    //  retry number is 1. The probability is very very low, and seems acceptable for now. It's
    //  a test issue only.
    table.get(new Get(ROW));

    LOG.info("we're done - time will change back");

    table.close();

    connection.close();
    EnvironmentEdgeManager.reset();
    TEST_UTIL.getAdmin().setBalancerRunning(previousBalance, true);
  }

    /**
     * Test that the connection to the dead server is cut immediately when we receive the
     *  notification.
     * @throws Exception
     */
  @Test
  public void testConnectionCut() throws Exception {
    final TableName tableName = TableName.valueOf(name.getMethodName());

    TEST_UTIL.createTable(tableName, FAM_NAM).close();
    boolean previousBalance = TEST_UTIL.getAdmin().setBalancerRunning(false, true);

    Configuration c2 = new Configuration(TEST_UTIL.getConfiguration());
    // We want to work on a separate connection.
    c2.set(HConstants.HBASE_CLIENT_INSTANCE_ID, String.valueOf(-1));
    // try only once w/o any retry
    c2.setInt(HConstants.HBASE_CLIENT_RETRIES_NUMBER, 0);
    c2.setInt(HConstants.HBASE_RPC_TIMEOUT_KEY, 30 * 1000);

    final Connection connection = ConnectionFactory.createConnection(c2);
    final Table table = connection.getTable(tableName);

    Put p = new Put(FAM_NAM);
    p.addColumn(FAM_NAM, FAM_NAM, FAM_NAM);
    table.put(p);

    final ConnectionImplementation hci =  (ConnectionImplementation) connection;

    final HRegionLocation loc;
    try(RegionLocator rl = connection.getRegionLocator(tableName)) {
      loc = rl.getRegionLocation(FAM_NAM);
    }

    Get get = new Get(FAM_NAM);
    Assert.assertNotNull(table.get(get));

    get = new Get(FAM_NAM);
    get.setFilter(new BlockingFilter());

    // This thread will mark the server as dead while we're waiting during a get.
    Thread t = new Thread() {
      @Override
      public void run() {
        synchronized (syncBlockingFilter) {
          try {
            syncBlockingFilter.wait();
          } catch (InterruptedException e) {
            throw new RuntimeException(e);
          }
        }
        hci.clusterStatusListener.deadServerHandler.newDead(loc.getServerName());
      }
    };

    t.start();
    try {
      table.get(get);
      Assert.fail();
    } catch (IOException expected) {
      LOG.debug("Received: " + expected);
      Assert.assertFalse(expected instanceof SocketTimeoutException);
      Assert.assertFalse(syncBlockingFilter.get());
    } finally {
      syncBlockingFilter.set(true);
      t.join();
      TEST_UTIL.getAdmin().setBalancerRunning(previousBalance, true);
    }

    table.close();
    connection.close();
  }

  protected static final AtomicBoolean syncBlockingFilter = new AtomicBoolean(false);

  public static class BlockingFilter extends FilterBase {
    @Override
    public boolean filterRowKey(byte[] buffer, int offset, int length) throws IOException {
      int i = 0;
      while (i++ < 1000 && !syncBlockingFilter.get()) {
        synchronized (syncBlockingFilter) {
          syncBlockingFilter.notifyAll();
        }
        Threads.sleep(100);
      }
      syncBlockingFilter.set(true);
      return false;
    }
    @Override
    public ReturnCode filterCell(final Cell ignored) throws IOException {
      return ReturnCode.INCLUDE;
    }

    public static Filter parseFrom(final byte [] pbBytes) throws DeserializationException{
      return new BlockingFilter();
    }
  }

  /**
   * Test that when we delete a location using the first row of a region
   * that we really delete it.
   * @throws Exception
   */
  @Test
  public void testRegionCaching() throws Exception {
    TEST_UTIL.createMultiRegionTable(TABLE_NAME, FAM_NAM).close();
    Configuration conf =  new Configuration(TEST_UTIL.getConfiguration());
    // test with no retry, or client cache will get updated after the first failure
    conf.setInt(HConstants.HBASE_CLIENT_RETRIES_NUMBER, 0);
    Connection connection = ConnectionFactory.createConnection(conf);
    final Table table = connection.getTable(TABLE_NAME);

    TEST_UTIL.waitUntilAllRegionsAssigned(table.getName());
    Put put = new Put(ROW);
    put.addColumn(FAM_NAM, ROW, ROW);
    table.put(put);

    ConnectionImplementation conn = (ConnectionImplementation) connection;

    assertNotNull(conn.getCachedLocation(TABLE_NAME, ROW));

    // Here we mess with the cached location making it so the region at TABLE_NAME, ROW is at
    // a location where the port is current port number +1 -- i.e. a non-existent location.
    HRegionLocation loc = conn.getCachedLocation(TABLE_NAME, ROW).getRegionLocation();
    final int nextPort = loc.getPort() + 1;
    conn.updateCachedLocation(loc.getRegionInfo(), loc.getServerName(),
        ServerName.valueOf("127.0.0.1", nextPort,
        HConstants.LATEST_TIMESTAMP), HConstants.LATEST_TIMESTAMP);
    Assert.assertEquals(conn.getCachedLocation(TABLE_NAME, ROW)
      .getRegionLocation().getPort(), nextPort);

    conn.clearRegionCache(TABLE_NAME, ROW.clone());
    RegionLocations rl = conn.getCachedLocation(TABLE_NAME, ROW);
    assertNull("What is this location?? " + rl, rl);

    // We're now going to move the region and check that it works for the client
    // First a new put to add the location in the cache
    conn.clearRegionCache(TABLE_NAME);
    Assert.assertEquals(0, conn.getNumberOfCachedRegionLocations(TABLE_NAME));
    Put put2 = new Put(ROW);
    put2.addColumn(FAM_NAM, ROW, ROW);
    table.put(put2);
    assertNotNull(conn.getCachedLocation(TABLE_NAME, ROW));
    assertNotNull(conn.getCachedLocation(TableName.valueOf(TABLE_NAME.getName()), ROW.clone()));

    TEST_UTIL.getAdmin().setBalancerRunning(false, false);
    HMaster master = TEST_UTIL.getMiniHBaseCluster().getMaster();

    // We can wait for all regions to be online, that makes log reading easier when debugging
    TEST_UTIL.waitUntilNoRegionsInTransition();

    // Now moving the region to the second server
    HRegionLocation toMove = conn.getCachedLocation(TABLE_NAME, ROW).getRegionLocation();
    byte[] regionName = toMove.getRegionInfo().getRegionName();
    byte[] encodedRegionNameBytes = toMove.getRegionInfo().getEncodedNameAsBytes();

    // Choose the other server.
    int curServerId = TEST_UTIL.getHBaseCluster().getServerWith(regionName);
    int destServerId = curServerId == 0? 1: 0;

    HRegionServer curServer = TEST_UTIL.getHBaseCluster().getRegionServer(curServerId);
    HRegionServer destServer = TEST_UTIL.getHBaseCluster().getRegionServer(destServerId);

    ServerName destServerName = destServer.getServerName();

    // Check that we are in the expected state
    Assert.assertTrue(curServer != destServer);
    Assert.assertFalse(curServer.getServerName().equals(destServer.getServerName()));
    Assert.assertFalse( toMove.getPort() == destServerName.getPort());
    Assert.assertNotNull(curServer.getOnlineRegion(regionName));
    Assert.assertNull(destServer.getOnlineRegion(regionName));
    Assert.assertFalse(TEST_UTIL.getMiniHBaseCluster().getMaster().
        getAssignmentManager().hasRegionsInTransition());

    // Moving. It's possible that we don't have all the regions online at this point, so
    //  the test must depend only on the region we're looking at.
    LOG.info("Move starting region="+toMove.getRegionInfo().getRegionNameAsString());
    TEST_UTIL.getAdmin().move(toMove.getRegionInfo().getEncodedNameAsBytes(), destServerName);

    while (destServer.getOnlineRegion(regionName) == null ||
        destServer.getRegionsInTransitionInRS().containsKey(encodedRegionNameBytes) ||
        curServer.getRegionsInTransitionInRS().containsKey(encodedRegionNameBytes) ||
        master.getAssignmentManager().hasRegionsInTransition()) {
      // wait for the move to be finished
      Thread.sleep(1);
    }

    LOG.info("Move finished for region="+toMove.getRegionInfo().getRegionNameAsString());

    // Check our new state.
    Assert.assertNull(curServer.getOnlineRegion(regionName));
    Assert.assertNotNull(destServer.getOnlineRegion(regionName));
    Assert.assertFalse(destServer.getRegionsInTransitionInRS().containsKey(encodedRegionNameBytes));
    Assert.assertFalse(curServer.getRegionsInTransitionInRS().containsKey(encodedRegionNameBytes));


    // Cache was NOT updated and points to the wrong server
    Assert.assertFalse(
        conn.getCachedLocation(TABLE_NAME, ROW).getRegionLocation()
          .getPort() == destServerName.getPort());

    // This part relies on a number of tries equals to 1.
    // We do a put and expect the cache to be updated, even if we don't retry
    LOG.info("Put starting");
    Put put3 = new Put(ROW);
    put3.addColumn(FAM_NAM, ROW, ROW);
    try {
      table.put(put3);
      Assert.fail("Unreachable point");
    } catch (RetriesExhaustedWithDetailsException e) {
      LOG.info("Put done, exception caught: " + e.getClass());
      Assert.assertEquals(1, e.getNumExceptions());
      Assert.assertEquals(1, e.getCauses().size());
      Assert.assertArrayEquals(ROW, e.getRow(0).getRow());

      // Check that we unserialized the exception as expected
      Throwable cause = ClientExceptionsUtil.findException(e.getCause(0));
      Assert.assertNotNull(cause);
      Assert.assertTrue(cause instanceof RegionMovedException);
    } catch (RetriesExhaustedException ree) {
      // hbase2 throws RetriesExhaustedException instead of RetriesExhaustedWithDetailsException
      // as hbase1 used to do. Keep an eye on this to see if this changed behavior is an issue.
      LOG.info("Put done, exception caught: " + ree.getClass());
      Throwable cause = ClientExceptionsUtil.findException(ree.getCause());
      Assert.assertNotNull(cause);
      Assert.assertTrue(cause instanceof RegionMovedException);
    }
    Assert.assertNotNull("Cached connection is null", conn.getCachedLocation(TABLE_NAME, ROW));
    Assert.assertEquals(
        "Previous server was " + curServer.getServerName().getHostAndPort(),
        destServerName.getPort(),
        conn.getCachedLocation(TABLE_NAME, ROW).getRegionLocation().getPort());

    Assert.assertFalse(destServer.getRegionsInTransitionInRS()
      .containsKey(encodedRegionNameBytes));
    Assert.assertFalse(curServer.getRegionsInTransitionInRS()
      .containsKey(encodedRegionNameBytes));

    // We move it back to do another test with a scan
    LOG.info("Move starting region=" + toMove.getRegionInfo().getRegionNameAsString());
    TEST_UTIL.getAdmin().move(toMove.getRegionInfo().getEncodedNameAsBytes(),
      curServer.getServerName());

    while (curServer.getOnlineRegion(regionName) == null ||
        destServer.getRegionsInTransitionInRS().containsKey(encodedRegionNameBytes) ||
        curServer.getRegionsInTransitionInRS().containsKey(encodedRegionNameBytes) ||
        master.getAssignmentManager().hasRegionsInTransition()) {
      // wait for the move to be finished
      Thread.sleep(1);
    }

    // Check our new state.
    Assert.assertNotNull(curServer.getOnlineRegion(regionName));
    Assert.assertNull(destServer.getOnlineRegion(regionName));
    LOG.info("Move finished for region=" + toMove.getRegionInfo().getRegionNameAsString());

    // Cache was NOT updated and points to the wrong server
    Assert.assertFalse(conn.getCachedLocation(TABLE_NAME, ROW).getRegionLocation().getPort() ==
      curServer.getServerName().getPort());

    Scan sc = new Scan();
    sc.setStopRow(ROW);
    sc.setStartRow(ROW);

    // The scanner takes the max retries from the connection configuration, not the table as
    // the put.
    TEST_UTIL.getConfiguration().setInt(HConstants.HBASE_CLIENT_RETRIES_NUMBER, 1);

    try {
      ResultScanner rs = table.getScanner(sc);
      while (rs.next() != null) {
      }
      Assert.fail("Unreachable point");
    } catch (RetriesExhaustedException e) {
      LOG.info("Scan done, expected exception caught: " + e.getClass());
    }

    // Cache is updated with the right value.
    Assert.assertNotNull(conn.getCachedLocation(TABLE_NAME, ROW));
    Assert.assertEquals(
      "Previous server was "+destServer.getServerName().getHostAndPort(),
      curServer.getServerName().getPort(),
      conn.getCachedLocation(TABLE_NAME, ROW).getRegionLocation().getPort());

    TEST_UTIL.getConfiguration().setInt(HConstants.HBASE_CLIENT_RETRIES_NUMBER, RPC_RETRY);
    table.close();
    connection.close();
  }

  /**
   * Test that Connection or Pool are not closed when managed externally
   * @throws Exception
   */
  @Test
  public void testConnectionManagement() throws Exception{
    Table table0 = TEST_UTIL.createTable(TABLE_NAME1, FAM_NAM);
    Connection conn = ConnectionFactory.createConnection(TEST_UTIL.getConfiguration());
    Table table = conn.getTable(TABLE_NAME1);
    table.close();
    assertFalse(conn.isClosed());
    if(table instanceof HTable) {
      assertFalse(((HTable) table).getPool().isShutdown());
    }
    table = conn.getTable(TABLE_NAME1);
    table.close();
    if(table instanceof HTable) {
      assertFalse(((HTable) table).getPool().isShutdown());
    }
    conn.close();
    if(table instanceof HTable) {
      assertTrue(((HTable) table).getPool().isShutdown());
    }
    table0.close();
  }

  /**
   * Test that stale cache updates don't override newer cached values.
   */
  @Test
  public void testCacheSeqNums() throws Exception{
    Table table = TEST_UTIL.createMultiRegionTable(TABLE_NAME2, FAM_NAM);
    Put put = new Put(ROW);
    put.addColumn(FAM_NAM, ROW, ROW);
    table.put(put);
    ConnectionImplementation conn = (ConnectionImplementation) TEST_UTIL.getConnection();

    HRegionLocation location = conn.getCachedLocation(TABLE_NAME2, ROW).getRegionLocation();
    assertNotNull(location);

    ServerName anySource = ServerName.valueOf(location.getHostname(), location.getPort() - 1, 0L);

    // Same server as already in cache reporting - overwrites any value despite seqNum.
    int nextPort = location.getPort() + 1;
    conn.updateCachedLocation(location.getRegionInfo(), location.getServerName(),
        ServerName.valueOf("127.0.0.1", nextPort, 0), location.getSeqNum() - 1);
    location = conn.getCachedLocation(TABLE_NAME2, ROW).getRegionLocation();
    Assert.assertEquals(nextPort, location.getPort());

    // No source specified - same.
    nextPort = location.getPort() + 1;
    conn.updateCachedLocation(location.getRegionInfo(), location.getServerName(),
        ServerName.valueOf("127.0.0.1", nextPort, 0), location.getSeqNum() - 1);
    location = conn.getCachedLocation(TABLE_NAME2, ROW).getRegionLocation();
    Assert.assertEquals(nextPort, location.getPort());

    // Higher seqNum - overwrites lower seqNum.
    nextPort = location.getPort() + 1;
    conn.updateCachedLocation(location.getRegionInfo(), anySource,
        ServerName.valueOf("127.0.0.1", nextPort, 0), location.getSeqNum() + 1);
    location = conn.getCachedLocation(TABLE_NAME2, ROW).getRegionLocation();
    Assert.assertEquals(nextPort, location.getPort());

    // Lower seqNum - does not overwrite higher seqNum.
    nextPort = location.getPort() + 1;
    conn.updateCachedLocation(location.getRegionInfo(), anySource,
        ServerName.valueOf("127.0.0.1", nextPort, 0), location.getSeqNum() - 1);
    location = conn.getCachedLocation(TABLE_NAME2, ROW).getRegionLocation();
    Assert.assertEquals(nextPort - 1, location.getPort());
    table.close();
  }

  @Test
  public void testClosing() throws Exception {
    Configuration configuration =
      new Configuration(TEST_UTIL.getConfiguration());
    configuration.set(HConstants.HBASE_CLIENT_INSTANCE_ID,
      String.valueOf(ThreadLocalRandom.current().nextInt()));

    // as connection caching is going away, now we're just testing
    // that closed connection does actually get closed.

    Connection c1 = ConnectionFactory.createConnection(configuration);
    Connection c2 = ConnectionFactory.createConnection(configuration);
    // no caching, different connections
    assertTrue(c1 != c2);

    // closing independently
    c1.close();
    assertTrue(c1.isClosed());
    assertFalse(c2.isClosed());

    c2.close();
    assertTrue(c2.isClosed());
  }

  /**
   * Trivial test to verify that nobody messes with
   * {@link ConnectionFactory#createConnection(Configuration)}
   */
  @Test
  public void testCreateConnection() throws Exception {
    Configuration configuration = TEST_UTIL.getConfiguration();
    Connection c1 = ConnectionFactory.createConnection(configuration);
    Connection c2 = ConnectionFactory.createConnection(configuration);
    // created from the same configuration, yet they are different
    assertTrue(c1 != c2);
    assertTrue(c1.getConfiguration() == c2.getConfiguration());
  }

  /**
   * This test checks that one can connect to the cluster with only the
   *  ZooKeeper quorum set. Other stuff like master address will be read
   *  from ZK by the client.
   */
  @Test
  public void testConnection() throws Exception{
    // We create an empty config and add the ZK address.
    Configuration c = new Configuration();
    // This test only makes sense for ZK based connection registry.
    c.set(HConstants.CLIENT_CONNECTION_REGISTRY_IMPL_CONF_KEY,
        HConstants.ZK_CONNECTION_REGISTRY_CLASS);
    c.set(HConstants.ZOOKEEPER_QUORUM,
      TEST_UTIL.getConfiguration().get(HConstants.ZOOKEEPER_QUORUM));
    c.set(HConstants.ZOOKEEPER_CLIENT_PORT,
      TEST_UTIL.getConfiguration().get(HConstants.ZOOKEEPER_CLIENT_PORT));
    // This should be enough to connect
    ClusterConnection conn = (ClusterConnection) ConnectionFactory.createConnection(c);
    assertTrue(conn.isMasterRunning());
    conn.close();
  }

  private int setNumTries(ConnectionImplementation hci, int newVal) throws Exception {
    Field numTries = hci.getClass().getDeclaredField("numTries");
    numTries.setAccessible(true);
    Field modifiersField = Field.class.getDeclaredField("modifiers");
    modifiersField.setAccessible(true);
    modifiersField.setInt(numTries, numTries.getModifiers() & ~Modifier.FINAL);
    final int prevNumRetriesVal = (Integer)numTries.get(hci);
    numTries.set(hci, newVal);

    return prevNumRetriesVal;
  }

  @Test
  public void testMulti() throws Exception {
    Table table = TEST_UTIL.createMultiRegionTable(TABLE_NAME3, FAM_NAM);
    try {
      ConnectionImplementation conn = (ConnectionImplementation)TEST_UTIL.getConnection();

      // We're now going to move the region and check that it works for the client
      // First a new put to add the location in the cache
      conn.clearRegionCache(TABLE_NAME3);
      Assert.assertEquals(0, conn.getNumberOfCachedRegionLocations(TABLE_NAME3));

      TEST_UTIL.getAdmin().setBalancerRunning(false, false);
      HMaster master = TEST_UTIL.getMiniHBaseCluster().getMaster();

      // We can wait for all regions to be online, that makes log reading easier when debugging
      TEST_UTIL.waitUntilNoRegionsInTransition();

      Put put = new Put(ROW_X);
      put.addColumn(FAM_NAM, ROW_X, ROW_X);
      table.put(put);

      // Now moving the region to the second server
      HRegionLocation toMove = conn.getCachedLocation(TABLE_NAME3, ROW_X).getRegionLocation();
      byte[] regionName = toMove.getRegionInfo().getRegionName();
      byte[] encodedRegionNameBytes = toMove.getRegionInfo().getEncodedNameAsBytes();

      // Choose the other server.
      int curServerId = TEST_UTIL.getHBaseCluster().getServerWith(regionName);
      int destServerId = (curServerId == 0 ? 1 : 0);

      HRegionServer curServer = TEST_UTIL.getHBaseCluster().getRegionServer(curServerId);
      HRegionServer destServer = TEST_UTIL.getHBaseCluster().getRegionServer(destServerId);

      ServerName destServerName = destServer.getServerName();
      ServerName metaServerName = TEST_UTIL.getHBaseCluster().getServerHoldingMeta();

       //find another row in the cur server that is less than ROW_X
      List<HRegion> regions = curServer.getRegions(TABLE_NAME3);
      byte[] otherRow = null;
       for (Region region : regions) {
         if (!region.getRegionInfo().getEncodedName().equals(toMove.getRegionInfo().getEncodedName())
             && Bytes.BYTES_COMPARATOR.compare(region.getRegionInfo().getStartKey(), ROW_X) < 0) {
           otherRow = region.getRegionInfo().getStartKey();
           break;
         }
       }
      assertNotNull(otherRow);
      // If empty row, set it to first row.-f
      if (otherRow.length <= 0) otherRow = Bytes.toBytes("aaa");
      Put put2 = new Put(otherRow);
      put2.addColumn(FAM_NAM, otherRow, otherRow);
      table.put(put2); //cache put2's location

      // Check that we are in the expected state
      Assert.assertTrue(curServer != destServer);
      Assert.assertNotEquals(curServer.getServerName(), destServer.getServerName());
      Assert.assertNotEquals(toMove.getPort(), destServerName.getPort());
      Assert.assertNotNull(curServer.getOnlineRegion(regionName));
      Assert.assertNull(destServer.getOnlineRegion(regionName));
      Assert.assertFalse(TEST_UTIL.getMiniHBaseCluster().getMaster().
          getAssignmentManager().hasRegionsInTransition());

       // Moving. It's possible that we don't have all the regions online at this point, so
      //  the test depends only on the region we're looking at.
      LOG.info("Move starting region=" + toMove.getRegionInfo().getRegionNameAsString());
      TEST_UTIL.getAdmin().move(toMove.getRegionInfo().getEncodedNameAsBytes(), destServerName);

      while (destServer.getOnlineRegion(regionName) == null ||
          destServer.getRegionsInTransitionInRS().containsKey(encodedRegionNameBytes) ||
          curServer.getRegionsInTransitionInRS().containsKey(encodedRegionNameBytes) ||
          master.getAssignmentManager().hasRegionsInTransition()) {
        // wait for the move to be finished
        Thread.sleep(1);
      }

      LOG.info("Move finished for region="+toMove.getRegionInfo().getRegionNameAsString());

      // Check our new state.
      Assert.assertNull(curServer.getOnlineRegion(regionName));
      Assert.assertNotNull(destServer.getOnlineRegion(regionName));
      Assert.assertFalse(destServer.getRegionsInTransitionInRS()
          .containsKey(encodedRegionNameBytes));
      Assert.assertFalse(curServer.getRegionsInTransitionInRS()
          .containsKey(encodedRegionNameBytes));


       // Cache was NOT updated and points to the wrong server
      Assert.assertFalse(
          conn.getCachedLocation(TABLE_NAME3, ROW_X).getRegionLocation()
              .getPort() == destServerName.getPort());

      // Hijack the number of retry to fail after 2 tries
      final int prevNumRetriesVal = setNumTries(conn, 2);

      Put put3 = new Put(ROW_X);
      put3.addColumn(FAM_NAM, ROW_X, ROW_X);
      Put put4 = new Put(otherRow);
      put4.addColumn(FAM_NAM, otherRow, otherRow);

      // do multi
      ArrayList<Put> actions = Lists.newArrayList(put4, put3);
      table.batch(actions, null); // first should be a valid row,
      // second we get RegionMovedException.

      setNumTries(conn, prevNumRetriesVal);
    } finally {
      table.close();
    }
  }

  @Test
  public void testErrorBackoffTimeCalculation() throws Exception {
    // TODO: This test would seem to presume hardcoded RETRY_BACKOFF which it should not.
    final long ANY_PAUSE = 100;
    ServerName location = ServerName.valueOf("127.0.0.1", 1, 0);
    ServerName diffLocation = ServerName.valueOf("127.0.0.1", 2, 0);

    ManualEnvironmentEdge timeMachine = new ManualEnvironmentEdge();
    EnvironmentEdgeManager.injectEdge(timeMachine);
    try {
      long largeAmountOfTime = ANY_PAUSE * 1000;
      ConnectionImplementation.ServerErrorTracker tracker =
          new ConnectionImplementation.ServerErrorTracker(largeAmountOfTime, 100);

      // The default backoff is 0.
      assertEquals(0, tracker.calculateBackoffTime(location, ANY_PAUSE));

      // Check some backoff values from HConstants sequence.
      tracker.reportServerError(location);
      assertEqualsWithJitter(ANY_PAUSE * HConstants.RETRY_BACKOFF[0],
        tracker.calculateBackoffTime(location, ANY_PAUSE));
      tracker.reportServerError(location);
      tracker.reportServerError(location);
      tracker.reportServerError(location);
      assertEqualsWithJitter(ANY_PAUSE * HConstants.RETRY_BACKOFF[3],
        tracker.calculateBackoffTime(location, ANY_PAUSE));

      // All of this shouldn't affect backoff for different location.
      assertEquals(0, tracker.calculateBackoffTime(diffLocation, ANY_PAUSE));
      tracker.reportServerError(diffLocation);
      assertEqualsWithJitter(ANY_PAUSE * HConstants.RETRY_BACKOFF[0],
        tracker.calculateBackoffTime(diffLocation, ANY_PAUSE));

      // Check with different base.
      assertEqualsWithJitter(ANY_PAUSE * 2 * HConstants.RETRY_BACKOFF[3],
          tracker.calculateBackoffTime(location, ANY_PAUSE * 2));
    } finally {
      EnvironmentEdgeManager.reset();
    }
  }

  private static void assertEqualsWithJitter(long expected, long actual) {
    assertEqualsWithJitter(expected, actual, expected);
  }

  private static void assertEqualsWithJitter(long expected, long actual, long jitterBase) {
    assertTrue("Value not within jitter: " + expected + " vs " + actual,
      Math.abs(actual - expected) <= (0.01f * jitterBase));
  }

  @Test
  public void testConnectionRideOverClusterRestart() throws IOException, InterruptedException {
    Configuration config = new Configuration(TEST_UTIL.getConfiguration());
    // This test only makes sense for ZK based connection registry.
    config.set(HConstants.CLIENT_CONNECTION_REGISTRY_IMPL_CONF_KEY,
        HConstants.ZK_CONNECTION_REGISTRY_CLASS);

    final TableName tableName = TableName.valueOf(name.getMethodName());
    TEST_UTIL.createTable(tableName, new byte[][] {FAM_NAM}).close();

    Connection connection = ConnectionFactory.createConnection(config);
    Table table = connection.getTable(tableName);

    // this will cache the meta location and table's region location
    table.get(new Get(Bytes.toBytes("foo")));

    // restart HBase
    TEST_UTIL.shutdownMiniHBaseCluster();
    TEST_UTIL.restartHBaseCluster(2);
    // this should be able to discover new locations for meta and table's region
    table.get(new Get(Bytes.toBytes("foo")));
    TEST_UTIL.deleteTable(tableName);
    table.close();
    connection.close();
  }

  @Test
  public void testLocateRegionsWithRegionReplicas() throws IOException {
    int regionReplication = 3;
    byte[] family = Bytes.toBytes("cf");
    TableName tableName = TableName.valueOf(name.getMethodName());

    // Create a table with region replicas
    TableDescriptorBuilder builder = TableDescriptorBuilder
      .newBuilder(tableName)
      .setRegionReplication(regionReplication)
      .setColumnFamily(ColumnFamilyDescriptorBuilder.of(family));
    TEST_UTIL.getAdmin().createTable(builder.build());

    try (ConnectionImplementation con = (ConnectionImplementation) ConnectionFactory.
      createConnection(TEST_UTIL.getConfiguration())) {
      // Get locations of the regions of the table
      List<HRegionLocation> locations = con.locateRegions(tableName, false, false);

      // The size of the returned locations should be 3
      assertEquals(regionReplication, locations.size());

      // The replicaIds of the returned locations should be 0, 1 and 2
      Set<Integer> expectedReplicaIds = IntStream.range(0, regionReplication).
        boxed().collect(Collectors.toSet());
      for (HRegionLocation location : locations) {
        assertTrue(expectedReplicaIds.remove(location.getRegion().getReplicaId()));
      }
    } finally {
      TEST_UTIL.deleteTable(tableName);
    }
  }

  @Test
  public void testMetaLookupThreadPoolCreated() throws Exception {
    final TableName tableName = TableName.valueOf(name.getMethodName());
    byte[][] FAMILIES = new byte[][] { Bytes.toBytes("foo") };
    if (TEST_UTIL.getAdmin().tableExists(tableName)) {
      TEST_UTIL.getAdmin().disableTable(tableName);
      TEST_UTIL.getAdmin().deleteTable(tableName);
    }
    try (Table htable = TEST_UTIL.createTable(tableName, FAMILIES)) {
      byte[] row = Bytes.toBytes("test");
      ConnectionImplementation c = ((ConnectionImplementation) TEST_UTIL.getConnection());
      // check that metalookup pool would get created
      c.relocateRegion(tableName, row);
      ExecutorService ex = c.getCurrentMetaLookupPool();
      assertNotNull(ex);
    }
  }

  // There is no assertion, but you need to confirm that there is no resource leak output from netty
  @Test
  public void testCancelConnectionMemoryLeak() throws IOException, InterruptedException {
    TableName tableName = TableName.valueOf(name.getMethodName());
    TEST_UTIL.createTable(tableName, FAM_NAM).close();
    TEST_UTIL.getAdmin().balancerSwitch(false, true);
    try (Connection connection = ConnectionFactory.createConnection(TEST_UTIL.getConfiguration());
      Table table = connection.getTable(tableName)) {
      table.get(new Get(Bytes.toBytes("1")));
      ServerName sn = TEST_UTIL.getRSForFirstRegionInTable(tableName).getServerName();
      RpcClient rpcClient = ((ConnectionImplementation) connection).getRpcClient();
      rpcClient.cancelConnections(sn);
      Thread.sleep(1000);
      System.gc();
      Thread.sleep(1000);
    }
  }
}