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From "Ashwin Chandra Putta (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (APEXMALHAR-2037) Pluggable component to queue tuples with ability to spool to disk
Date Tue, 05 Apr 2016 22:48:25 GMT

     [ https://issues.apache.org/jira/browse/APEXMALHAR-2037?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Ashwin Chandra Putta updated APEXMALHAR-2037:
    Summary: Pluggable component to queue tuples with ability to spool to disk  (was: Reconciled
jdbc output operator with ability to spool to disk)

> Pluggable component to queue tuples with ability to spool to disk
> -----------------------------------------------------------------
>                 Key: APEXMALHAR-2037
>                 URL: https://issues.apache.org/jira/browse/APEXMALHAR-2037
>             Project: Apache Apex Malhar
>          Issue Type: New Feature
>            Reporter: Ashwin Chandra Putta
>            Assignee: Ashwin Chandra Putta
> There are many use cases in which we are writing tuples to external system using JDBC
etc. There are instances when the external system might be slow and down for some time. In
those cases, the current implementation of jdbc output operators fail and restart until the
external system is up again. Meanwhile, the DAG is slowed down by this operator. To deal with
such scenarios, we should write the output in a reconciled fashion where the reconciler thread
is writing at the pace of external system. We should also provide an ability to spool the
data to disk when the external system is down or the output operators queue is full.
> Here are the proposed features for the output operator.
> 1. Write to external system in a separate reconciler thread.
> 2. Queue the tuples in memory for reconciler thread to consume. 
> 3. Spool the incoming tuples to hdfs using a WAL when the queue is full.
> 4. Read from WAL and write to queue as queue is being consumed.
> 5. When external system is able to consume as fast as incoming throughput, WAL is not
written. The queue will just buffer the tuples before writing to external system.

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