package org.apache.cassandra.hadoop;
/*
*
* 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.
*
*/
import java.io.IOException;
import java.net.InetAddress;
import java.nio.ByteBuffer;
import java.util.*;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;
import org.apache.cassandra.client.RingCache;
import org.apache.cassandra.dht.Range;
import org.apache.cassandra.thrift.*;
import org.apache.cassandra.utils.ByteBufferUtil;
import org.apache.cassandra.utils.Pair;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.thrift.TException;
import org.apache.thrift.transport.TSocket;
/**
* The <code>ColumnFamilyRecordWriter</code> maps the output <key, value>
* pairs to a Cassandra column family. In particular, it applies all mutations
* in the value, which it associates with the key, and in turn the responsible
* endpoint.
*
* <p>
* Furthermore, this writer groups the mutations by the endpoint responsible for
* the rows being affected. This allows the mutations to be executed in parallel,
* directly to a responsible endpoint.
* </p>
*
* @see ColumnFamilyOutputFormat
* @see OutputFormat
*
*/
final class ColumnFamilyRecordWriter extends RecordWriter<ByteBuffer,List<Mutation>>
implements org.apache.hadoop.mapred.RecordWriter<ByteBuffer,List<Mutation>>
{
// The configuration this writer is associated with.
private final Configuration conf;
// The ring cache that describes the token ranges each node in the ring is
// responsible for. This is what allows us to group the mutations by
// the endpoints they should be targeted at. The targeted endpoint
// essentially
// acts as the primary replica for the rows being affected by the mutations.
private final RingCache ringCache;
// The number of mutations to buffer per endpoint
private final int queueSize;
// handles for clients for each range running in the threadpool
private final Map<Range,RangeClient> clients;
private final long batchThreshold;
private final ConsistencyLevel consistencyLevel;
/**
* Upon construction, obtain the map that this writer will use to collect
* mutations, and the ring cache for the given keyspace.
*
* @param context the task attempt context
* @throws IOException
*/
ColumnFamilyRecordWriter(TaskAttemptContext context) throws IOException
{
this(context.getConfiguration());
}
ColumnFamilyRecordWriter(Configuration conf) throws IOException
{
this.conf = conf;
this.ringCache = new RingCache(ConfigHelper.getOutputKeyspace(conf),
ConfigHelper.getPartitioner(conf),
ConfigHelper.getInitialAddress(conf),
ConfigHelper.getRpcPort(conf));
this.queueSize = conf.getInt(ColumnFamilyOutputFormat.QUEUE_SIZE, 32 * Runtime.getRuntime().availableProcessors());
this.clients = new HashMap<Range,RangeClient>();
batchThreshold = conf.getLong(ColumnFamilyOutputFormat.BATCH_THRESHOLD, 32);
consistencyLevel = ConsistencyLevel.valueOf(ConfigHelper.getWriteConsistencyLevel(conf));
}
/**
* If the key is to be associated with a valid value, a mutation is created
* for it with the given column family and columns. In the event the value
* in the column is missing (i.e., null), then it is marked for
* {@link Deletion}. Similarly, if the entire value for a key is missing
* (i.e., null), then the entire key is marked for {@link Deletion}.
* </p>
*
* @param keybuff
* the key to write.
* @param value
* the value to write.
* @throws IOException
*/
@Override
public void write(ByteBuffer keybuff, List<Mutation> value) throws IOException
{
Range range = ringCache.getRange(keybuff);
// get the client for the given range, or create a new one
RangeClient client = clients.get(range);
if (client == null)
{
// haven't seen keys for this range: create new client
client = new RangeClient(ringCache.getEndpoint(range));
client.start();
clients.put(range, client);
}
for (Mutation amut : value)
client.put(new Pair<ByteBuffer,Mutation>(keybuff, amut));
}
/**
* Close this <code>RecordWriter</code> to future operations, but not before
* flushing out the batched mutations.
*
* @param context the context of the task
* @throws IOException
*/
@Override
public void close(TaskAttemptContext context) throws IOException, InterruptedException
{
close();
}
/** Fills the deprecated RecordWriter interface for streaming. */
@Deprecated
public void close(org.apache.hadoop.mapred.Reporter reporter) throws IOException
{
close();
}
private void close() throws IOException
{
// close all the clients before throwing anything
IOException clientException = null;
for (RangeClient client : clients.values())
{
try
{
client.close();
}
catch (IOException e)
{
clientException = e;
}
}
if (clientException != null)
throw clientException;
}
/**
* A client that runs in a threadpool and connects to the list of endpoints for a particular
* range. Mutations for keys in that range are sent to this client via a queue.
*/
public class RangeClient extends Thread
{
// The list of endpoints for this range
private final List<InetAddress> endpoints;
private final String columnFamily = ConfigHelper.getOutputColumnFamily(conf);
// A bounded queue of incoming mutations for this range
private final BlockingQueue<Pair<ByteBuffer, Mutation>> queue = new ArrayBlockingQueue<Pair<ByteBuffer,Mutation>>(queueSize);
private volatile boolean run = true;
// we want the caller to know if something went wrong, so we record any unrecoverable exception while writing
// so we can throw it on the caller's stack when he calls put() again, or if there are no more put calls,
// when the client is closed.
private volatile IOException lastException;
private Cassandra.Client thriftClient;
private TSocket thriftSocket;
/**
* Constructs an {@link RangeClient} for the given endpoints.
* @param endpoints the possible endpoints to execute the mutations on
*/
public RangeClient(List<InetAddress> endpoints)
{
super("client-" + endpoints);
this.endpoints = endpoints;
}
/**
* enqueues the given value to Cassandra
*/
public void put(Pair<ByteBuffer,Mutation> value) throws IOException
{
while (true)
{
if (lastException != null)
throw lastException;
try
{
if (queue.offer(value, 100, TimeUnit.MILLISECONDS))
break;
}
catch (InterruptedException e)
{
throw new AssertionError(e);
}
}
}
public void close() throws IOException
{
// stop the run loop. this will result in closeInternal being called by the time join() finishes.
run = false;
interrupt();
try
{
this.join();
}
catch (InterruptedException e)
{
throw new AssertionError(e);
}
if (lastException != null)
throw lastException;
}
private void closeInternal()
{
if (thriftSocket != null)
{
thriftSocket.close();
thriftSocket = null;
thriftClient = null;
}
}
/**
* Loops collecting mutations from the queue and sending to Cassandra
*/
public void run()
{
outer:
while (run || !queue.isEmpty())
{
Pair<ByteBuffer, Mutation> mutation;
try
{
mutation = queue.take();
}
catch (InterruptedException e)
{
// re-check loop condition after interrupt
continue;
}
Map<ByteBuffer, Map<String, List<Mutation>>> batch = new HashMap<ByteBuffer, Map<String, List<Mutation>>>();
while (mutation != null)
{
Map<String, List<Mutation>> subBatch = batch.get(mutation.left);
if (subBatch == null)
{
subBatch = Collections.singletonMap(columnFamily, (List<Mutation>) new ArrayList<Mutation>());
batch.put(mutation.left, subBatch);
}
subBatch.get(columnFamily).add(mutation.right);
if (batch.size() >= batchThreshold)
break;
mutation = queue.poll();
}
Iterator<InetAddress> iter = endpoints.iterator();
while (true)
{
// send the mutation to the last-used endpoint. first time through, this will NPE harmlessly.
try
{
thriftClient.batch_mutate(batch, consistencyLevel);
break;
}
catch (Exception e)
{
closeInternal();
if (!iter.hasNext())
{
lastException = new IOException(e);
break outer;
}
}
// attempt to connect to a different endpoint
try
{
InetAddress address = iter.next();
thriftSocket = new TSocket(address.getHostName(), ConfigHelper.getRpcPort(conf));
thriftClient = ColumnFamilyOutputFormat.createAuthenticatedClient(thriftSocket, conf);
}
catch (Exception e)
{
closeInternal();
// TException means something unexpected went wrong to that endpoint, so
// we should try again to another. Other exceptions (auth or invalid request) are fatal.
if ((!(e instanceof TException)) || !iter.hasNext())
{
lastException = new IOException(e);
break outer;
}
}
}
}
}
@Override
public String toString()
{
return "#<Client for " + endpoints.toString() + ">";
}
}
}