/**
    * 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 java.io.IOException;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicLong;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.HBaseTestingUtility;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.client.backoff.ClientBackoffPolicy;
  import org.apache.hadoop.hbase.client.backoff.ExponentialClientBackoffPolicy;
  import org.apache.hadoop.hbase.client.backoff.ServerStatistics;
  import org.apache.hadoop.hbase.client.coprocessor.Batch;
  import org.apache.hadoop.hbase.regionserver.HRegionServer;
  import org.apache.hadoop.hbase.regionserver.Region;
  import org.apache.hadoop.hbase.testclassification.MediumTests;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.junit.AfterClass;
  import org.junit.BeforeClass;
  import org.junit.Test;
  import org.junit.experimental.categories.Category;
  
  import static org.apache.hadoop.hbase.client.MetricsConnection.CLIENT_SIDE_METRICS_ENABLED_KEY;
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertNotEquals;
  import static org.junit.Assert.assertNotNull;
  import static org.junit.Assert.assertTrue;
  
  /**
   * Test that we can actually send and use region metrics to slowdown client writes
   */
  @Category(MediumTests.class)
  public class TestClientPushback {
  
    private static final Log LOG = LogFactory.getLog(TestClientPushback.class);
    private static final HBaseTestingUtility UTIL = new HBaseTestingUtility();
  
    private static final byte[] tableName = Bytes.toBytes("client-pushback");
    private static final byte[] family = Bytes.toBytes("f");
    private static final byte[] qualifier = Bytes.toBytes("q");
    private static long flushSizeBytes = 1024;
  
    @BeforeClass
    public static void setupCluster() throws Exception{
      Configuration conf = UTIL.getConfiguration();
      // enable backpressure
      conf.setBoolean(HConstants.ENABLE_CLIENT_BACKPRESSURE, true);
      // use the exponential backoff policy
      conf.setClass(ClientBackoffPolicy.BACKOFF_POLICY_CLASS, ExponentialClientBackoffPolicy.class,
        ClientBackoffPolicy.class);
      // turn the memstore size way down so we don't need to write a lot to see changes in memstore
      // load
      conf.setLong(HConstants.HREGION_MEMSTORE_FLUSH_SIZE, flushSizeBytes);
      // ensure we block the flushes when we are double that flushsize
      conf.setLong(HConstants.HREGION_MEMSTORE_BLOCK_MULTIPLIER, HConstants.DEFAULT_HREGION_MEMSTORE_BLOCK_MULTIPLIER);
      conf.setBoolean(CLIENT_SIDE_METRICS_ENABLED_KEY, true);
      UTIL.startMiniCluster();
      UTIL.createTable(tableName, family);
    }
  
    @AfterClass
    public static void teardownCluster() throws Exception{
      UTIL.shutdownMiniCluster();
    }
  
    @Test(timeout=60000)
    public void testClientTracksServerPushback() throws Exception{
      Configuration conf = UTIL.getConfiguration();
      TableName tablename = TableName.valueOf(tableName);
      Connection conn = ConnectionFactory.createConnection(conf);
      HTable table = (HTable) conn.getTable(tablename);
      //make sure we flush after each put
      table.setAutoFlushTo(true);
  
     // write some data
     Put p = new Put(Bytes.toBytes("row"));
     p.add(family, qualifier, Bytes.toBytes("value1"));
     table.put(p);
 
     // get the stats for the region hosting our table
     ClusterConnection connection = table.connection;
     ClientBackoffPolicy backoffPolicy = connection.getBackoffPolicy();
     assertTrue("Backoff policy is not correctly configured",
       backoffPolicy instanceof ExponentialClientBackoffPolicy);
     
     ServerStatisticTracker stats = connection.getStatisticsTracker();
     assertNotNull( "No stats configured for the client!", stats);
     Region region = UTIL.getHBaseCluster().getRegionServer(0).getOnlineRegions(tablename).get(0);
     // get the names so we can query the stats
     ServerName server = UTIL.getHBaseCluster().getRegionServer(0).getServerName();
     byte[] regionName = region.getRegionInfo().getRegionName();
 
     // check to see we found some load on the memstore
     ServerStatistics serverStats = stats.getServerStatsForTesting(server);
     ServerStatistics.RegionStatistics regionStats = serverStats.getStatsForRegion(regionName);
     int load = regionStats.getMemstoreLoadPercent();
     assertEquals("We did not find some load on the memstore", load,
       regionStats.getMemstoreLoadPercent());
 
     // check that the load reported produces a nonzero delay
     long backoffTime = backoffPolicy.getBackoffTime(server, regionName, serverStats);
     assertNotEquals("Reported load does not produce a backoff", backoffTime, 0);
     LOG.debug("Backoff calculated for " + region.getRegionInfo().getRegionNameAsString() + " @ " +
       server + " is " + backoffTime);
 
     // Reach into the connection and submit work directly to AsyncProcess so we can
     // monitor how long the submission was delayed via a callback
     List<Row> ops = new ArrayList<Row>(1);
     ops.add(p);
     final CountDownLatch latch = new CountDownLatch(1);
     final AtomicLong endTime = new AtomicLong();
     long startTime = EnvironmentEdgeManager.currentTime();    
     table.mutator.ap.submit(tablename, ops, true, new Batch.Callback<Result>() {
       @Override
       public void update(byte[] region, byte[] row, Result result) {
         endTime.set(EnvironmentEdgeManager.currentTime());
         latch.countDown();
       }
     }, true);
     // Currently the ExponentialClientBackoffPolicy under these test conditions
     // produces a backoffTime of 151 milliseconds. This is long enough so the
     // wait and related checks below are reasonable. Revisit if the backoff
     // time reported by above debug logging has significantly deviated.
     String name = server.getServerName() + "," + Bytes.toStringBinary(regionName);
     MetricsConnection.RegionStats rsStats = connection.getConnectionMetrics().
             serverStats.get(server).get(regionName);
     assertEquals(name, rsStats.name);
     assertEquals(rsStats.heapOccupancyHist.mean(),
         (double)regionStats.getHeapOccupancyPercent(), 0.1 );
     assertEquals(rsStats.memstoreLoadHist.mean(),
         (double)regionStats.getMemstoreLoadPercent(), 0.1);
 
     MetricsConnection.RunnerStats runnerStats = connection.getConnectionMetrics().runnerStats;
 
     assertEquals(runnerStats.delayRunners.count(), 1);
     assertEquals(runnerStats.normalRunners.count(), 1);
     assertEquals("", runnerStats.delayIntevalHist.mean(), (double)backoffTime, 0.1);
 
     latch.await(backoffTime * 2, TimeUnit.MILLISECONDS);
     assertNotEquals("AsyncProcess did not submit the work time", endTime.get(), 0);
     assertTrue("AsyncProcess did not delay long enough", endTime.get() - startTime >= backoffTime);
   }
 
   @Test
   public void testMutateRowStats() throws IOException {
     Configuration conf = UTIL.getConfiguration();
     ClusterConnection conn = (ClusterConnection) ConnectionFactory.createConnection(conf);
     HTable table = (HTable) conn.getTable(tableName);
     HRegionServer rs = UTIL.getHBaseCluster().getRegionServer(0);
     Region region = rs.getOnlineRegions(TableName.valueOf(tableName)).get(0);
 
     RowMutations mutations = new RowMutations(Bytes.toBytes("row"));
     Put p = new Put(Bytes.toBytes("row"));
     p.addColumn(family, qualifier, Bytes.toBytes("value2"));
     mutations.add(p);
     table.mutateRow(mutations);
 
     ServerStatisticTracker stats = conn.getStatisticsTracker();
     assertNotNull( "No stats configured for the client!", stats);
     // get the names so we can query the stats
     ServerName server = rs.getServerName();
     byte[] regionName = region.getRegionInfo().getRegionName();
 
     // check to see we found some load on the memstore
     ServerStatistics serverStats = stats.getServerStatsForTesting(server);
     ServerStatistics.RegionStatistics regionStats = serverStats.getStatsForRegion(regionName);
 
     assertNotNull(regionStats);
     assertTrue(regionStats.getMemstoreLoadPercent() > 0);
     }
 }