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https://issues.apache.org/jira/browse/SPARK-3051?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Owen updated SPARK-3051:
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Target Version/s: (was: 1.2.0)
> Support looking-up named accumulators in a registry
> ---------------------------------------------------
>
> Key: SPARK-3051
> URL: https://issues.apache.org/jira/browse/SPARK-3051
> Project: Spark
> Issue Type: Improvement
> Components: Spark Core
> Affects Versions: 1.0.0
> Reporter: Neil Ferguson
>
> This is a proposed enhancement to Spark based on the following mailing list
> discussion:
> http://apache-spark-developers-list.1001551.n3.nabble.com/quot-Dynamic-variables-quot-in-Spark-td7450.html.
> This proposal builds on SPARK-2380 (Support displaying accumulator values in
> the web UI) to allow named accumulables to be looked-up in a "registry", as
> opposed to having to be passed to every method that need to access them.
> The use case was described well by [~shivaram], as follows:
> Lets say you have two functions you use
> in a map call and want to measure how much time each of them takes. For
> example, if you have a code block like the one below and you want to
> measure how much time f1 takes as a fraction of the task.
> {noformat}
> a.map { l =>
> val f = f1(l)
> ... some work here ...
> }
> {noformat}
> It would be really cool if we could do something like
> {noformat}
> a.map { l =>
> val start = System.nanoTime
> val f = f1(l)
> TaskMetrics.get("f1-time").add(System.nanoTime - start)
> }
> {noformat}
> SPARK-2380 provides a partial solution to this problem -- however the
> accumulables would still need to be passed to every function that needs them,
> which I think would be cumbersome in any application of reasonable complexity.
> The proposal, as suggested by [~pwendell], is to have a "registry" of
> accumulables, that can be looked-up by name.
> Regarding the implementation details, I'd propose that we broadcast a
> serialized version of all named accumulables in the DAGScheduler (similar to
> what SPARK-2521 does for Tasks). These can then be deserialized in the
> Executor.
> Accumulables are already stored in thread-local variables in the Accumulators
> object, so exposing these in the registry should be simply a matter of
> wrapping this object, and keying the accumulables by name (they are currently
> keyed by ID).
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