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 <j...@nanthrax.net > <mailto:j...@nanthrax.net>> 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 <re...@google.com > <mailto:re...@google.com> > > <mailto:re...@google.com <mailto:re...@google.com>>> 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.jan...@gmail.com <mailto:vojta.jan...@gmail.com> > <mailto:vojta.jan...@gmail.com <mailto:vojta.jan...@gmail.com>>> 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 > jbono...@apache.org <mailto:jbono...@apache.org> > http://blog.nanthrax.net > Talend - http://www.talend.com > -- Jean-Baptiste Onofré jbono...@apache.org http://blog.nanthrax.net Talend - http://www.talend.com
