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From DB Tsai <dbt...@stanford.edu>
Subject Re: Passing runtime config to workers?
Date Mon, 19 May 2014 00:16:48 GMT
When you reference any variable outside the executor's scope, spark will
automatically serialize them in the driver, and send them to executors,
which implies, those variables have to implement serializable.

For the example you mention, the Spark will serialize object F, and if it's
not serializable, it will raise exception.


Sincerely,

DB Tsai
-------------------------------------------------------
My Blog: https://www.dbtsai.com
LinkedIn: https://www.linkedin.com/in/dbtsai


On Sun, May 18, 2014 at 12:58 PM, Robert James <srobertjames@gmail.com>wrote:

> I see - I didn't realize that scope would work like that.  Are you
> saying that any variable that is in scope of the lambda passed to map
> will be automagically propagated to all workers? What if it's not
> explicitly referenced in the map, only used by it.  E.g.:
>
> def main:
>   settings.setSettings
>   rdd.map(x => F.f(x))
>
> object F {
>   def f(...)...
>   val settings:...
> }
>
> F.f accesses F.settings, like a Singleton.  The master sets F.settings
> before using F.f in a map.  Will all workers have the same F.settings
> as seen by F.f?
>
>
>
> On 5/16/14, DB Tsai <dbtsai@stanford.edu> wrote:
> > Since the evn variables in driver will not be passed into workers, the
> most
> > easy way you can do is refer to the variables directly in workers from
> > driver.
> >
> > For example,
> >
> > val variableYouWantToUse = System.getenv("something defined in env")
> >
> > rdd.map(
> > you can access `variableYouWantToUse` here
> > )
> >
> >
> >
> > Sincerely,
> >
> > DB Tsai
> > -------------------------------------------------------
> > My Blog: https://www.dbtsai.com
> > LinkedIn: https://www.linkedin.com/in/dbtsai
> >
> >
> > On Fri, May 16, 2014 at 1:59 PM, Robert James
> > <srobertjames@gmail.com>wrote:
> >
> >> What is a good way to pass config variables to workers?
> >>
> >> I've tried setting them in environment variables via spark-env.sh, but,
> >> as
> >> far as I can tell, the environment variables set there don't appear in
> >> workers' environments.  If I want to be able to configure all workers,
> >> what's a good way to do it?  For example, I want to tell all workers:
> >> USE_ALGO_A or USE_ALGO_B - but I don't want to recompile.
> >>
> >
>

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