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From Reynold Xin <r...@databricks.com>
Subject Re: [Spark Streaming] Dynamic Broadcast Variable Update
Date Fri, 05 May 2017 16:40:27 GMT
Thanks for the email. The process is to create a JIRA ticket and then post
a design doc for discussion. You will of course need to update your code to
work with the latest master branch, but you should wait oj that until the
community has a chance to comment on the design.

Cheers.


On Fri, May 5, 2017 at 8:01 AM Nipun Arora <nipunarora2512@gmail.com> wrote:

> Hi All,
>
> To support our Spark Streaming based anomaly detection tool, we have made
> a patch in Spark 1.6.2 to dynamically update broadcast variables.
>
> I'll first explain our use-case, which I believe should be common to
> several people using Spark Streaming applications. Broadcast variables are
> often used to store values "machine learning models", which can then be
> used on streaming data to "test" and get the desired results (for our case
> anomalies). Unfortunately, in the current spark, broadcast variables are
> final and can only be initialized once before the initialization of the
> streaming context. Hence, if a new model is learned the streaming system
> cannot be updated without shutting down the application, broadcasting
> again, and restarting the application. Our goal was to re-broadcast
> variables without requiring a downtime of the streaming service.
>
> The key to this implementation is a live re-broadcastVariable() interface,
> which can be triggered in between micro-batch executions, without any
> re-boot required for the streaming application. At a high level the task is
> done by re-fetching broadcast variable information from the spark driver,
> and then re-distribute it to the workers. The micro-batch execution is
> blocked while the update is made, by taking a lock on the execution. We
> have already tested this in our prototype deployment of our anomaly
> detection service and can successfully re-broadcast the broadcast variables
> with no downtime.
>
> We would like to integrate these changes in spark, can anyone please let
> me know the process of submitting patches/ new features to spark. Also. I
> understand that the current version of Spark is 2.1. However, our changes
> have been done and tested on Spark 1.6.2, will this be a problem?
>
> Thanks
> Nipun
>

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