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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-9083) Add async backpressure support to Cassandra Connector
Date Tue, 02 Oct 2018 07:16:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-9083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16635087#comment-16635087
] 

ASF GitHub Bot commented on FLINK-9083:
---------------------------------------

jparkie opened a new pull request #6782: [FLINK-9083][Cassandra Connector] Add async backpressure
support to Cassandra Connector
URL: https://github.com/apache/flink/pull/6782
 
 
   ## What is the purpose of the change
   
   This pull requests rewrites `CassandraSinkBase` to use a `Phaser` and `Semaphore` to provide
proper synchronization to support `maxConcurrentRequests` as a new configuration. This improves
the reliability of the Cassandra Connector as it can currently overwhelm a weak Cassandra
cluster if the upstream source has very high throughput.
   
   ## Brief change log
   
     - Rewrote `CassandraSinkBase` to use a `Phaser` and `Semaphore`.
     - Expose `public void setMaxConcurrentRequests(int maxConcurrentRequests, long timeout,
TimeUnit unit)` on `CassandraSinkBase`.
     - Modify `CassandraSink` with the new configuration. It currently does not support the
WAL.
     - Updated the documentation about the new configuration.
   
   ## Verifying this change
   
   This change is already covered by existing tests, such as `CassandraSinkBaseTest` and `CassandraConnectorITCase`.
   
   This change added tests and can be verified as follows:
   
     - Added tests for acquiring permits from the `Semaphore` and releasing permits from the
`Semaphore` when a write succeeds or fails.
   
   ## Does this pull request potentially affect one of the following parts:
   
     - Dependencies (does it add or upgrade a dependency): no
     - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: no
     - The serializers: no
     - The runtime per-record code paths (performance sensitive): no
     - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing,
Yarn/Mesos, ZooKeeper: no
     - The S3 file system connector: no
   
   ## Documentation
   
     - Does this pull request introduce a new feature? yes
     - If yes, how is the feature documented? docs / JavaDocs
   

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> Add async backpressure support to Cassandra Connector
> -----------------------------------------------------
>
>                 Key: FLINK-9083
>                 URL: https://issues.apache.org/jira/browse/FLINK-9083
>             Project: Flink
>          Issue Type: Improvement
>          Components: Cassandra Connector
>            Reporter: Jacob Park
>            Assignee: Jacob Park
>            Priority: Minor
>              Labels: pull-request-available
>
> As the CassandraSinkBase derivatives utilize async writes, they do not block the task
to introduce any backpressure.
> I am currently using a semaphore to provide backpressure support by blocking at a maximum
concurrent requests limit like how DataStax's Spark Cassandra Connector functions: [https://github.com/datastax/spark-cassandra-connector/blob/v2.0.7/spark-cassandra-connector/src/main/scala/com/datastax/spark/connector/writer/AsyncExecutor.scala#L18]
> This improvement has greatly improved the fault-tolerance of our Cassandra Sink Connector
implementation on Apache Flink in production. I would like to contribute this feature back
upstream.



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