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https://issues.apache.org/jira/browse/FLINK-4500?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16248266#comment-16248266
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ASF GitHub Bot commented on FLINK-4500:
---------------------------------------
Github user mcfongtw commented on the issue:
https://github.com/apache/flink/pull/4605
Hi, @zentol , thanks for reviewing this PR. I recalled that I put a [caveat
](https://ci.apache.org/projects/flink/flink-docs-release-1.4/dev/connectors/cassandra.html#checkpointing-and-fault-tolerance)about
this potential data loss in the latest C* connector documents. Since this fix
is committed, would you like me to open another PR just to remove that warning
message from document?
> 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
> Fix For: 1.4.0
>
>
> 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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