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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-4500) Cassandra sink can lose messages
Date Tue, 19 Sep 2017 11:06:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-4500?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16171519#comment-16171519
] 

ASF GitHub Bot commented on FLINK-4500:
---------------------------------------

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

    https://github.com/apache/flink/pull/4605#discussion_r139660015
  
    --- Diff: flink-connectors/flink-connector-cassandra/src/main/java/org/apache/flink/streaming/connectors/cassandra/CassandraSinkBase.java
---
    @@ -37,29 +41,49 @@
      *
      * @param <IN> Type of the elements emitted by this sink
      */
    -public abstract class CassandraSinkBase<IN, V> extends RichSinkFunction<IN>
{
    +public abstract class CassandraSinkBase<IN, V> extends RichSinkFunction<IN>
implements CheckpointedFunction {
     	protected final Logger log = LoggerFactory.getLogger(getClass());
     	protected transient Cluster cluster;
     	protected transient Session session;
     
    -	protected transient volatile Throwable exception;
    +	protected transient volatile Throwable asyncError;
     	protected transient FutureCallback<V> callback;
     
    -	private final ClusterBuilder builder;
    +	protected final ClusterBuilder builder;
     
     	private final AtomicInteger updatesPending = new AtomicInteger();
     
    +	/**
    +	 * If true, the producer will wait until all outstanding action requests have been sent
to C*.
    +	 */
    +	private boolean flushOnCheckpoint = true;
    --- End diff --
    
    Ideally all sinks should behave the same way, but that would be out of scope for PR in
particular.


> Cassandra sink can lose messages
> --------------------------------
>
>                 Key: FLINK-4500
>                 URL: https://issues.apache.org/jira/browse/FLINK-4500
>             Project: Flink
>          Issue Type: Bug
>          Components: Cassandra Connector
>    Affects Versions: 1.1.0
>            Reporter: Elias Levy
>            Assignee: Michael Fong
>
> The problem is the same as I pointed out with the Kafka producer sink (FLINK-4027). 
The CassandraTupleSink's send() and CassandraPojoSink's send() both send data asynchronously
to Cassandra and record whether an error occurs via a future callback.  But CassandraSinkBase
does not implement Checkpointed, so it can't stop checkpoint from happening even though the
are Cassandra queries in flight from the checkpoint that may fail.  If they do fail, they
would subsequently not be replayed when the job recovered, and would thus be lost.
> In addition, 
> CassandraSinkBase's close should check whether there is a pending exception and throw
it, rather than silently close.  It should also wait for any pending async queries to complete
and check their status before closing.



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