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Re: Performance issue in Beam 2.4 onwards


If we added something slow to the core library in order to better test DirectRunner, that does sound like an unfortunate bug.

On Mon, Jul 9, 2018 at 11:21 PM Vojtech Janota <vojta.janota@xxxxxxxxx> wrote:
Hi guys,

Thank you for all of your feedback. I have created relevant issue in JIRA: https://issues.apache.org/jira/browse/BEAM-4750

@Lukasz: me mentioning the DirectRunner was somewhat unfortunate - the bottleneck was introduced into the core library and so Flink and Spark runners would be impacted too

Thanks,
Vojta

On Mon, Jul 9, 2018 at 5:48 PM, Lukasz Cwik <lcwik@xxxxxxxxxx> wrote:
Instead of reverting/working around specific checks/tests that the DirectRunner is doing, have you considered using one of the other runners like Flink or Spark with a local execution cluster. You won't hit the validation/verification bottlenecks that DirectRunner specifically imposes.

On Mon, Jul 9, 2018 at 8:46 AM Jean-Baptiste Onofré <jb@xxxxxxxxxxxx> wrote:
Thanks for the update Eugene.

@Vojta: do you mind to create a Jira ? I will tackle a fix for that.

Regards
JB

On 09/07/2018 17:33, Eugene Kirpichov wrote:
> Hi -
>
> If I remember correctly, the reason for this change was to ensure that
> the state is encodable at all. Prior to the change, there had been
> situations where the coder specified on a state cell is buggy, absent or
> set incorrectly (due to some issue in coder inference), but direct
> runner did not detect this because it never tried to encode the state
> cells - this would have blown up in any distributed runner.
>
> I think it should be possible to relax this and clone only values being
> added to the state, rather than cloning the whole state on copy(). I
> don't have time to work on this change myself, but I can review a PR if
> someone else does.
>
> On Mon, Jul 9, 2018 at 8:28 AM Jean-Baptiste Onofré <jb@xxxxxxxxxxxx
> <mailto:jb@xxxxxxxxxxxx>> wrote:
>
>     Hi Vojta,
>
>     I fully agree, that's why it makes sense to wait Eugene's feedback.
>
>     I remember we had some performance regression on the direct runner
>     identified thanks to Nexmark, but it has been addressed by reverting a
>     change.
>
>     Good catch anyway !
>
>     Regards
>     JB
>
>     On 09/07/2018 17:20, Vojtech Janota wrote:
>     > Hi Reuven,
>     >
>     > I'm not really complaining about DirectRunner. In fact it seems to
>     me as
>     > if what previously was considered as part of the "expensive extra
>     > checks" done by the DirectRunner is now done within the
>     > beam-runners-core-java library. Considering that all objects involved
>     > are immutable (in our case at least) and simple assignment is
>     > sufficient, the serialization-deserialization really seems as unwanted
>     > and hugely expensive correctness check. If there was a problem with
>     > identity copy, wasn't DirectRunner supposed to reveal it? 
>     >
>     > Regards,
>     > Vojta
>     >
>     > On Mon, Jul 9, 2018 at 4:46 PM, Reuven Lax <relax@xxxxxxxxxx
>     <mailto:relax@xxxxxxxxxx>
>     > <mailto:relax@xxxxxxxxxx <mailto:relax@xxxxxxxxxx>>> wrote:
>     >
>     >     Hi Vojita,
>     >
>     >     One problem is that the DirectRunner is designed for testing, not
>     >     for performance. The DirectRunner currently does many
>     >     purposely-inefficient things, the point of which is to better
>     expose
>     >     potential bugs in tests. For example, the DirectRunner will
>     randomly
>     >     shuffle the order of PCollections to ensure that your code
>     does not
>     >     rely on ordering.  All of this adds cost, because the current
>     runner
>     >     is designed for testing. There have been requests in the past
>     for an
>     >     "optimized" local runner, however we don't currently have such
>     a thing.
>     >
>     >     In this case, using coders to clone values is more correct. In a
>     >     distributed environment using encode/decode is the only way to
>     copy
>     >     values, and the DirectRunner is trying to ensure that your code is
>     >     correct in a distributed environment.
>     >
>     >     Reuven
>     >
>     >     On Mon, Jul 9, 2018 at 7:22 AM Vojtech Janota
>     >     <vojta.janota@xxxxxxxxx <mailto:vojta.janota@xxxxxxxxx>
>     <mailto:vojta.janota@xxxxxxxxx <mailto:vojta.janota@xxxxxxxxx>>> wrote:
>     >
>     >         Hi,
>     >
>     >         We are using Apache Beam in our project for some time now.
>     Since
>     >         our datasets are of modest size, we have so far used
>     >         DirectRunner as the computation easily fits onto a single
>     >         machine. Recently we upgraded Beam from 2.2 to 2.4 and
>     found out
>     >         that performance of our pipelines drastically deteriorated.
>     >         Pipelines that took ~3 minutes with 2.2 do not finish within
>     >         hours now. We tried to isolate the change that causes the
>     >         slowdown and came to the commits into the
>     >         "InMemoryStateInternals" class:
>     >
>     >         * https://github.com/apache/beam/commit/32a427c
>     >         <https://github.com/apache/beam/commit/32a427c>
>     >         * https://github.com/apache/beam/commit/8151d82
>     >         <https://github.com/apache/beam/commit/8151d82>
>     >
>     >         In a nutshell where previously the copy() method simply
>     assigned:
>     >
>     >           that.value = this.value
>     >
>     >         There is now coder encode/decode combo hidden behind:
>     >
>     >           that.value = uncheckedClone(coder, this.value)
>     >
>     >         Can somebody explain the purpose of this change? Is it
>     meant as
>     >         an additional "enforcement" point, similar to DirectRunner's
>     >         enforceImmutability and enforceEncodability? Or is it
>     something
>     >         that is genuinely needed to provide correct behaviour of the
>     >         pipeline?
>     >
>     >         Any hints or thoughts are appreciated.
>     >
>     >         Regards,
>     >         Vojta
>     >
>     >          
>     >
>     >
>     >
>     >
>
>     --
>     Jean-Baptiste Onofré
>     jbonofre@xxxxxxxxxx <mailto:jbonofre@xxxxxxxxxx>
>     http://blog.nanthrax.net
>     Talend - http://www.talend.com
>

--
Jean-Baptiste Onofré
jbonofre@xxxxxxxxxx
http://blog.nanthrax.net
Talend - http://www.talend.com