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   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
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   *
   *     http://www.apache.org/licenses/LICENSE-2.0
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   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
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  package org.apache.cassandra.hints;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.util.*;
  import java.util.concurrent.TimeUnit;
  import java.util.zip.CRC32;
  
  import com.google.common.collect.Iterables;
  import org.junit.BeforeClass;
  import org.junit.Test;
  
  import org.apache.cassandra.SchemaLoader;
  import org.apache.cassandra.concurrent.NamedThreadFactory;
  import org.apache.cassandra.db.Mutation;
  import org.apache.cassandra.db.RowUpdateBuilder;
  import org.apache.cassandra.db.marshal.ValueAccessors;
  import org.apache.cassandra.db.rows.Cell;
  import org.apache.cassandra.db.rows.Row;
  import org.apache.cassandra.io.util.DataInputBuffer;
  import org.apache.cassandra.io.util.DataInputPlus;
  import org.apache.cassandra.net.MessagingService;
  import org.apache.cassandra.schema.KeyspaceParams;
  import org.apache.cassandra.schema.Schema;
  import org.apache.cassandra.schema.TableMetadata;
  
  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 static org.junit.Assert.fail;
  
  import static org.apache.cassandra.utils.ByteBufferUtil.bytes;
  import static org.apache.cassandra.utils.FBUtilities.updateChecksum;
  
  public class HintsBufferTest
  {
      private static final String KEYSPACE = "hints_buffer_test";
      private static final String TABLE = "table";
  
      private static final int HINTS_COUNT = 300_000;
      private static final int HINT_THREADS_COUNT = 10;
      private static final int HOST_ID_COUNT = 10;
  
      @BeforeClass
      public static void defineSchema()
      {
          SchemaLoader.prepareServer();
          SchemaLoader.createKeyspace(KEYSPACE, KeyspaceParams.simple(1), SchemaLoader.standardCFMD(KEYSPACE, TABLE));
      }
  
      @Test
      public void testOverlyLargeAllocation()
      {
          // create a small, 128 bytes buffer
          HintsBuffer buffer = HintsBuffer.create(128);
  
          // try allocating an entry of 65 bytes (53 bytes hint + 12 bytes of overhead)
          try
          {
              buffer.allocate(65 - HintsBuffer.ENTRY_OVERHEAD_SIZE);
              fail("Allocation of the buffer should have failed but hasn't");
          }
          catch (IllegalArgumentException e)
          {
              assertEquals(String.format("Hint of %s bytes is too large - the maximum size is 64", 65 - HintsBuffer.ENTRY_OVERHEAD_SIZE),
                           e.getMessage());
          }
  
          // assert that a 1-byte smaller allocation fits properly
          try (HintsBuffer.Allocation allocation = buffer.allocate(64 - HintsBuffer.ENTRY_OVERHEAD_SIZE))
          {
              assertNotNull(allocation);
          }
      }
  
      @Test
      public void testWrite() throws IOException, InterruptedException
      {
          // generate 10 random host ids to choose from
          UUID[] hostIds = new UUID[HOST_ID_COUNT];
          for (int i = 0; i < hostIds.length; i++)
              hostIds[i] = UUID.randomUUID();
  
          // map each index to one random UUID from the previously created UUID array
          Random random = new Random(System.currentTimeMillis());
          UUID[] load = new UUID[HINTS_COUNT];
          for (int i = 0; i < load.length; i++)
              load[i] = hostIds[random.nextInt(HOST_ID_COUNT)];
  
          // calculate the size of a single hint (they will all have an equal size in this test)
          int hintSize = (int) Hint.serializer.serializedSize(createHint(0, System.currentTimeMillis()), MessagingService.current_version);
          int entrySize = hintSize + HintsBuffer.ENTRY_OVERHEAD_SIZE;
  
          // allocate a slab to fit *precisely* HINTS_COUNT hints
          int slabSize = entrySize * HINTS_COUNT;
          HintsBuffer buffer = HintsBuffer.create(slabSize);
  
          // use a fixed timestamp base for all mutation timestamps
          long baseTimestamp = System.currentTimeMillis();
  
          // create HINT_THREADS_COUNT, start them, and wait for them to finish
          List<Thread> threads = new ArrayList<>(HINT_THREADS_COUNT);
          for (int i = 0; i < HINT_THREADS_COUNT; i ++)
              threads.add(NamedThreadFactory.createAnonymousThread(new Writer(buffer, load, hintSize, i, baseTimestamp)));
          threads.forEach(java.lang.Thread::start);
          for (Thread thread : threads)
              thread.join();
  
          // sanity check that we are full
          assertEquals(slabSize, buffer.capacity());
          assertEquals(0, buffer.remaining());
  
          // try to allocate more bytes, ensure that the allocation fails
          assertNull(buffer.allocate(1));
  
          // a failed allocation should automatically close the oporder
          buffer.waitForModifications();
  
          // a failed allocation should also automatically make the buffer as closed
          assertTrue(buffer.isClosed());
  
          // assert that host id set in the buffer equals to hostIds
          assertEquals(HOST_ID_COUNT, buffer.hostIds().size());
          assertEquals(new HashSet<>(Arrays.asList(hostIds)), buffer.hostIds());
  
          // iterate over *every written hint*, validate its content
          for (UUID hostId : hostIds)
          {
              Iterator<ByteBuffer> iter = buffer.consumingHintsIterator(hostId);
              while (iter.hasNext())
              {
                  int idx = validateEntry(hostId, iter.next(), baseTimestamp, load);
                  load[idx] = null; // nullify each visited entry
              }
          }
  
          // assert that all the entries in load array have been visited and nullified
          for (UUID hostId : load)
              assertNull(hostId);
  
          // free the buffer
          buffer.free();
      }
  
      private static int validateEntry(UUID hostId, ByteBuffer buffer, long baseTimestamp, UUID[] load) throws IOException
      {
          CRC32 crc = new CRC32();
          DataInputPlus di = new DataInputBuffer(buffer, true);
  
          // read and validate size
          int hintSize = di.readInt();
          assertEquals(hintSize + HintsBuffer.ENTRY_OVERHEAD_SIZE, buffer.remaining());
  
          // read and validate size crc
          updateChecksum(crc, buffer, buffer.position(), 4);
          assertEquals((int) crc.getValue(), di.readInt());
  
          // read the hint and update/validate overall crc
          Hint hint = Hint.serializer.deserialize(di, MessagingService.current_version);
          updateChecksum(crc, buffer, buffer.position() + 8, hintSize);
          assertEquals((int) crc.getValue(), di.readInt());
  
          // further validate hint correctness
          int idx = (int) (hint.creationTime - baseTimestamp);
          assertEquals(hostId, load[idx]);
  
          Row row = hint.mutation.getPartitionUpdates().iterator().next().iterator().next();
          assertEquals(1, Iterables.size(row.cells()));
  
          ValueAccessors.assertDataEquals(bytes(idx), row.clustering().get(0));
          Cell<?> cell = row.cells().iterator().next();
          assertEquals(TimeUnit.MILLISECONDS.toMicros(baseTimestamp + idx), cell.timestamp());
          ValueAccessors.assertDataEquals(bytes(idx), cell.buffer());
  
          return idx;
      }
  
      static Hint createHint(int idx, long baseTimestamp)
      {
          long timestamp = baseTimestamp + idx;
          return Hint.create(createMutation(idx, TimeUnit.MILLISECONDS.toMicros(timestamp)), timestamp);
      }
  
      private static Mutation createMutation(int index, long timestamp)
      {
          TableMetadata table = Schema.instance.getTableMetadata(KEYSPACE, TABLE);
          return new RowUpdateBuilder(table, timestamp, bytes(index))
                     .clustering(bytes(index))
                     .add("val", bytes(index))
                     .build();
      }
  
      static class Writer implements Runnable
      {
          final HintsBuffer buffer;
          final UUID[] load;
          final int hintSize;
          final int index;
          final long baseTimestamp;
  
          Writer(HintsBuffer buffer, UUID[] load, int hintSize, int index, long baseTimestamp)
          {
              this.buffer = buffer;
              this.load = load;
              this.hintSize = hintSize;
              this.index = index;
              this.baseTimestamp = baseTimestamp;
          }
  
          public void run()
          {
              int hintsPerThread = HINTS_COUNT / HINT_THREADS_COUNT;
              for (int i = index * hintsPerThread; i < (index + 1) * hintsPerThread; i++)
              {
                  try (HintsBuffer.Allocation allocation = buffer.allocate(hintSize))
                  {
                      Hint hint = createHint(i, baseTimestamp);
                      allocation.write(Collections.singleton(load[i]), hint);
                  }
              }
          }
      }
  }
  