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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3311) Add a connector for streaming data into Cassandra
Date Tue, 05 Apr 2016 14:35:26 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15226369#comment-15226369
] 

ASF GitHub Bot commented on FLINK-3311:
---------------------------------------

Github user rmetzger commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1771#discussion_r58548581
  
    --- Diff: flink-streaming-connectors/flink-connector-cassandra/src/main/java/org/apache/flink/batch/connectors/cassandra/CassandraOutputFormat.java
---
    @@ -0,0 +1,123 @@
    +/*
    + * 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.flink.batch.connectors.cassandra;
    +
    +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.base.Strings;
    +import com.google.common.util.concurrent.FutureCallback;
    +import com.google.common.util.concurrent.Futures;
    +import org.apache.flink.api.common.io.RichOutputFormat;
    +import org.apache.flink.api.java.tuple.Tuple;
    +import org.apache.flink.configuration.Configuration;
    +import org.apache.flink.streaming.connectors.cassandra.ClusterBuilder;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import java.io.IOException;
    +
    +/**
    + * OutputFormat to write {@link org.apache.flink.api.java.tuple.Tuple} into Apache Cassandra.
    + *
    + * @param <OUT> type of Tuple
    + */
    +public class CassandraOutputFormat<OUT extends Tuple> extends RichOutputFormat<OUT>
{
    +	private static final Logger LOG = LoggerFactory.getLogger(CassandraOutputFormat.class);
    +
    +	private final String insertQuery;
    +	private final ClusterBuilder builder;
    +
    +	private transient Cluster cluster;
    +	private transient Session session;
    +	private transient PreparedStatement prepared;
    +	private transient FutureCallback<ResultSet> callback;
    +	private transient Throwable exception = null;
    +
    +	public CassandraOutputFormat(String insertQuery, ClusterBuilder builder) {
    +		if (Strings.isNullOrEmpty(insertQuery)) {
    +			throw new IllegalArgumentException("insertQuery cannot be null or empty");
    +		}
    +		if (builder == null) {
    +			throw new IllegalArgumentException("Builder cannot be null.");
    +		}
    +		this.insertQuery = insertQuery;
    +		this.builder = builder;
    +	}
    +
    +	@Override
    +	public void configure(Configuration parameters) {
    +		this.cluster = builder.getCluster();
    +	}
    +
    +	/**
    +	 * Opens a Session to Cassandra and initializes the prepared statement.
    +	 *
    +	 * @param taskNumber The number of the parallel instance.
    +	 * @throws IOException Thrown, if the output could not be opened due to an
    +	 *                     I/O problem.
    +	 */
    +	@Override
    +	public void open(int taskNumber, int numTasks) throws IOException {
    +		this.session = cluster.connect();
    +		this.prepared = session.prepare(insertQuery);
    +		this.callback = new FutureCallback<ResultSet>() {
    +			@Override
    +			public void onSuccess(ResultSet ignored) {
    +			}
    +
    +			@Override
    +			public void onFailure(Throwable t) {
    +				exception = t;
    +			}
    +		};
    +	}
    +
    +	@Override
    +	public void writeRecord(OUT record) throws IOException {
    +		if (exception != null) {
    +			throw new IOException("write record failed", exception);
    +		}
    +
    +		Object[] fields = new Object[record.getArity()];
    +		for (int i = 0; i < record.getArity(); i++) {
    +			fields[i] = record.getField(i);
    +		}
    +		ResultSetFuture result = session.executeAsync(prepared.bind(fields));
    +		Futures.addCallback(result, callback);
    +	}
    +
    +	/**
    +	 * Closes all resources used.
    +	 */
    +	@Override
    +	public void close() throws IOException {
    +		try {
    +			session.close();
    +		} catch (Exception e) {
    +			LOG.info("Inputformat couldn't be closed - " + e.getMessage());
    --- End diff --
    
    I would make this a WARN and forward the cause to the log entry


> Add a connector for streaming data into Cassandra
> -------------------------------------------------
>
>                 Key: FLINK-3311
>                 URL: https://issues.apache.org/jira/browse/FLINK-3311
>             Project: Flink
>          Issue Type: New Feature
>          Components: Streaming Connectors
>            Reporter: Robert Metzger
>            Assignee: Andrea Sella
>
> We had users in the past asking for a Flink+Cassandra integration.
> It seems that there is a well-developed java client for connecting into Cassandra: https://github.com/datastax/java-driver
(ASL 2.0)
> There are also tutorials out there on how to start a local cassandra instance (for the
tests): http://prettyprint.me/prettyprint.me/2010/02/14/running-cassandra-as-an-embedded-service/index.html
> For the data types, I think we should support TupleX types, and map standard java types
to the respective cassandra types.
> In addition, it seems that there is a object mapper from datastax to store POJOs in Cassandra
(there are annotations for defining the primary key and types)



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