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https://issues.apache.org/jira/browse/SPARK-19108?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15806774#comment-15806774
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Shivaram Venkataraman commented on SPARK-19108:
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+1 - This is a good idea. One thing I'd like to add is that it might be better
to create one broadcast rather than two broadcasts for sake of efficiency. For
each broadcast variable we contact the driver to get location information and
then initiate some fetches -- Thus to keep the number of messages lower having
one broadcast variable will be better.
> Broadcast all shared parts of tasks (to reduce task serialization time)
> -----------------------------------------------------------------------
>
> Key: SPARK-19108
> URL: https://issues.apache.org/jira/browse/SPARK-19108
> Project: Spark
> Issue Type: Improvement
> Components: Scheduler
> Reporter: Kay Ousterhout
>
> Expand the amount of information that's broadcasted for tasks, to avoid
> serializing data per-task that should only be sent to each executor once for
> the entire stage.
> Conceptually, this means we'd have new classes specially for sending the
> minimal necessary data to the executor, like:
> {code}
> /**
> * metadata about the taskset needed by the executor for all tasks in this
> taskset. Subset of the
> * full data kept on the driver to make it faster to serialize and send to
> executors.
> */
> class ExecutorTaskSetMeta(
> val stageId: Int,
> val stageAttemptId: Int,
> val properties: Properties,
> val addedFiles: Map[String, String],
> val addedJars: Map[String, String]
> // maybe task metrics here?
> )
> class ExecutorTaskData(
> val partitionId: Int,
> val attemptNumber: Int,
> val taskId: Long,
> val taskBinary: Broadcast[Array[Byte]],
> val taskSetMeta: Broadcast[ExecutorTaskSetMeta]
> )
> {code}
> Then all the info you'd need to send to the executors would be a serialized
> version of ExecutorTaskData. Furthermore, given the simplicity of that
> class, you could serialize manually, and then for each task you could just
> modify the first two ints & one long directly in the byte buffer. (You could
> do the same trick for serialization even if ExecutorTaskSetMeta was not a
> broadcast, but that will keep the msgs small as well.)
> There a bunch of details I'm skipping here: you'd also need to do some
> special handling for the TaskMetrics; the way tasks get started in the
> executor would change; you'd also need to refactor {{Task}} to let it get
> reconstructed from this information (or add more to ExecutorTaskSetMeta); and
> probably other details I'm overlooking now.
> (this is copied from SPARK-18890 and [~imranr]'s comment there; cc
> [~shivaram])
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