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From rmetzger <...@git.apache.org>
Subject [GitHub] flink pull request: [FLINK-3311/FLINK-3332] Add Cassandra connecto...
Date Tue, 05 Apr 2016 15:41:35 GMT
Github user rmetzger commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1771#discussion_r58561933
  
    --- Diff: flink-streaming-connectors/flink-connector-cassandra/src/main/java/org/apache/flink/streaming/connectors/cassandra/CassandraTupleWriteAheadSink.java
---
    @@ -0,0 +1,136 @@
    +/**
    + * 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
    + * <p/>
    + * http://www.apache.org/licenses/LICENSE-2.0
    + * <p/>
    + * 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.flink.streaming.connectors.cassandra;
    +
    +import com.datastax.driver.core.BoundStatement;
    +import com.datastax.driver.core.Cluster;
    +import com.datastax.driver.core.PreparedStatement;
    +import com.datastax.driver.core.ResultSet;
    +import com.datastax.driver.core.ResultSetFuture;
    +import com.datastax.driver.core.Session;
    +import com.google.common.util.concurrent.FutureCallback;
    +import com.google.common.util.concurrent.Futures;
    +import org.apache.flink.api.common.typeutils.TypeSerializer;
    +import org.apache.flink.api.java.ClosureCleaner;
    +import org.apache.flink.api.java.tuple.Tuple;
    +import org.apache.flink.api.java.typeutils.runtime.TupleSerializer;
    +import org.apache.flink.streaming.runtime.operators.CheckpointCommitter;
    +import org.apache.flink.streaming.runtime.operators.GenericAtLeastOnceSink;
    +
    +import java.util.concurrent.atomic.AtomicInteger;
    +
    +/**
    + * Sink that emits its input elements into a Cassandra database. This sink stores incoming
records within a 
    + * {@link org.apache.flink.runtime.state.AbstractStateBackend}, and only commits them
to cassandra
    + * if a checkpoint is completed.
    + *
    + * @param <IN> Type of the elements emitted by this sink
    + */
    +public class CassandraTupleWriteAheadSink<IN extends Tuple> extends GenericAtLeastOnceSink<IN>
{
    +	protected transient Cluster cluster;
    +	protected transient Session session;
    +
    +	private final String insertQuery;
    +	private transient PreparedStatement preparedStatement;
    +
    +	private transient Throwable exception = null;
    +	private transient FutureCallback<ResultSet> callback;
    +
    +	private ClusterBuilder builder;
    +
    +	private int updatesSent = 0;
    +	private AtomicInteger updatesConfirmed = new AtomicInteger(0);
    +
    +	private transient Object[] fields;
    +
    +	protected CassandraTupleWriteAheadSink(String insertQuery, TypeSerializer<IN>
serializer, ClusterBuilder builder, String jobID, CheckpointCommitter committer) throws Exception
{
    +		super(committer, serializer, jobID);
    +		this.insertQuery = insertQuery;
    +		this.builder = builder;
    +		ClosureCleaner.clean(builder, true);
    +	}
    +
    +	public void open() throws Exception {
    +		super.open();
    +		if (!getRuntimeContext().isCheckpointingEnabled()) {
    +			throw new IllegalStateException("The write-ahead log requires checkpointing to be
enabled.");
    +		}
    +		this.callback = new FutureCallback<ResultSet>() {
    +			@Override
    +			public void onSuccess(ResultSet resultSet) {
    +				updatesConfirmed.incrementAndGet();
    +			}
    +
    +			@Override
    +			public void onFailure(Throwable throwable) {
    +				exception = throwable;
    +			}
    +		};
    +		cluster = builder.getCluster();
    +		session = cluster.connect();
    +		preparedStatement = session.prepare(insertQuery);
    +
    +		fields = new Object[((TupleSerializer<IN>) serializer).getArity()];
    +	}
    +
    +	@Override
    +	public void close() throws Exception {
    +		super.close();
    +		try {
    +			session.close();
    +		} catch (Exception e) {
    +			LOG.error("Error while closing session.", e);
    +		}
    +		try {
    +			cluster.close();
    +		} catch (Exception e) {
    +			LOG.error("Error while closing cluster.", e);
    +		}
    +	}
    +
    +	@Override
    +	protected void sendValues(Iterable<IN> values, long timestamp) throws Exception
{
    +		//verify that no query failed until now
    +		if (exception != null) {
    +			throw new Exception(exception);
    +		}
    +		//set values for prepared statement
    +		for (IN value : values) {
    +			for (int x = 0; x < value.getArity(); x++) {
    +				fields[x] = value.getField(x);
    +			}
    +			//insert values and send to cassandra
    +			BoundStatement s = preparedStatement.bind(fields);
    +			s.setDefaultTimestamp(timestamp);
    +			ResultSetFuture result = session.executeAsync(s);
    +			updatesSent++;
    +			if (result != null) {
    +				//add callback to detect errors
    +				Futures.addCallback(result, callback);
    +			}
    +		}
    +		while (updatesSent != updatesConfirmed.get()) {
    +			try {
    +				Thread.sleep(100);
    +			} catch (InterruptedException e) {
    --- End diff --
    
    I would leave the while loop on an interrupt.
    It might happen that the thread gets locked in the loop because it can not be interrupted.


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