Hmmm. Fair. I'm mostly concerned about the pathological case where we end
up with a distinct Environment per transform, but there are likely
practical cases where that's reasonable (High mem to GPU to TPU, to ARM....)
On Wed, Nov 25, 2020, 10:42 AM Robert Bradshaw <rober...@google.com> wrote:
> I'd like to continue the discussion *and* see an implementation for
> the part we've settled on. I was asking why not have "every distinct
> physical concern means a distinct environment?"
>
> On Wed, Nov 25, 2020 at 10:38 AM Robert Burke <rob...@frantil.com> wrote:
> >
> > Mostly because perfect is the enemy of good enough. We have a proposal,
> we have clear boundaries for it. It's fine if the discussion continues, but
> I see no evidence of concerns that should prevent starting an
> implementation, because it seems we'll need both anyway.
> >
> > On Wed, Nov 25, 2020, 10:25 AM Robert Bradshaw <rober...@google.com>
> wrote:
> >>
> >> On Wed, Nov 25, 2020 at 10:15 AM Robert Burke <rob...@frantil.com>
> wrote:
> >> >
> >> > It sounds like we've come to the position that non-correctness
> affecting Ptransform Annotations are valuable at both leaf and composite
> levels, and don't remove the potential need for a similar feature on
> Environments, to handle physical concerns equirements for worker processes
> to have (such as Ram, CPU, or GPU requirements.)
> >> >
> >> > Kenn, it's not clear what part of the solution (an annotation field
> on the Ptransform proto message) would need to change to satisfy your scope
> concern, beyond documenting unambiguously that these may not be used for
> physical concerns or things that affect correctness.
> >>
> >> I'll let Kenn answer as well, but from my point of view, explicitly
> >> having somewhere better to put these things would help.
> >>
> >> > I'm also unclear your scope concern not matching, given the above.
> Your first paragraph reads very supportive of logical annotations on
> Ptransforms, and that matches 1-1 with the current proposed solution. Can
> you clarify your concern?
> >> >
> >> > I don't wish to scope creep on the physical requirements issue at
> this time. It seems we are agreed they should end up on environments, but
> I'm not seeing proposals on the right way to execute them at this time.They
> seem to be a fruitful topic of discussion, in particular
> unifying/consolidating them for efficient use of resources. I don't think
> we want to end up in a state where every distinct physical concern means a
> distinct environment.
> >>
> >> Why not? Assuming, of course, that runners are free to merge
> >> environments (merging those resource hints they understand and are
> >> otherwise compatible, and discarding those they don't) for efficient
> >> execution.
> >>
> >> > I for one am ready to see a PR.
> >>
> >> +1
> >>
> >> > On Mon, Nov 23, 2020, 6:02 PM Kenneth Knowles <k...@apache.org>
> wrote:
> >> >>
> >> >>
> >> >>
> >> >> On Mon, Nov 23, 2020 at 3:04 PM Robert Bradshaw <rober...@google.com>
> wrote:
> >> >>>
> >> >>> On Fri, Nov 20, 2020 at 11:08 AM Mirac Vuslat Basaran <
> mir...@google.com> wrote:
> >> >>> >
> >> >>> > Thanks everyone so much for their input and for the insightful
> discussion.
> >> >>> >
> >> >>> > Not being knowledgeable about Beam's internals, I have to say I
> am a bit lost on the PTransform vs. environment discussion.
> >> >>> >
> >> >>> > I do agree with Burke's notion that merge rules are very
> annotation dependent, I don't think we can find a one-size-fits-all
> solution for that. So this might be actually be an argument in favour of
> having annotations on PTransforms, since it avoids the conflation with
> environments.
> >> >>> >
> >> >>> > Also in general, I feel that having annotations per single
> transform (rather than composite) and on PTransforms could lead to a
> simpler design.
> >> >>>
> >> >>> If we want to use these for privacy, I don't see how attaching them
> to
> >> >>> leaf transforms alone could work. (Even CombinePerKey is a
> composite.)
> >> >>>
> >> >>> > Seeing as there are valuable arguments in favour of both
> (PTransform and environments) with no clear(?) "best solution", I would
> propose moving forward with the initial (PTransform) design to ship the
> feature and unblock teams asking for it. If it turns out that there was
> indeed a need to have annotations in environments, we could always refactor
> it.
> >> >>>
> >> >>> I have yet to see any arguments that resource-level hints, such as
> >> >>> memory or GPU, don't better belong on the environment. But moving
> >> >>> forward on PTransform-level ones for logical statements like privacy
> >> >>> declarations makes sense.
> >> >>
> >> >>
> >> >> Exactly this. Properties of transforms make sense. The properties
> may hold only of the whole subgraph. Even something as simple as "preserves
> keys". This is analogous (but converse) to requirements like "requires
> sorted input" which were explicitly excluded from the scope, which was
> about hardware environment for execution.
> >> >>
> >> >> The proposed scope and the proposed solution do not match and need
> to be reconciled.
> >> >>
> >> >> Kenn
> >> >>
> >> >>> > On 2020/11/17 19:07:22, Robert Bradshaw <rober...@google.com>
> wrote:
> >> >>> > > So far we have two distinct usecases for annotations: resource
> hints
> >> >>> > > and privacy directives, and I've been trying to figure out how
> to
> >> >>> > > reconcile them, but they seem to have very different
> characteristics.
> >> >>> > > (It would be nice to come up with other uses as well to see if
> we're
> >> >>> > > really coming up with a generally useful mode--I think display
> data
> >> >>> > > could fit into this as a new kind of annotation rather than
> being a
> >> >>> > > top-level property, and it could make sense on both leaf and
> composite
> >> >>> > > transforms.)
> >> >>> > >
> >> >>> > > To me, resource hints like GPU are inextricably tied to the
> >> >>> > > environment. A transform tagged with GPU should reference a Fn
> that
> >> >>> > > invokes GPU-accelerated code that lives in a particular
> environment.
> >> >>> > > Something like high-mem is a bit squishier. Some DoFns take a
> lot of
> >> >>> > > memory, but on the other hand one could imagine labeling a
> CoGBK as
> >> >>> > > high-mem due to knowing that, in this particular usage, there
> will be
> >> >>> > > lots of values with the same key. Ideally runners would be
> intelligent
> >> >>> > > enough to automatically learn memory usage, but even in this
> case it
> >> >>> > > may be a good hint to try and learn the requirements for DoFn A
> and
> >> >>> > > DoFn B separately (which is difficult if they are always
> colocated,
> >> >>> > > but valuable if, e.g. A takes a huge amount of memory and B
> takes a
> >> >>> > > huge amount of wall time).
> >> >>> > >
> >> >>> > > Note that tying things to the environment does not preclude
> using them
> >> >>> > > in non-portable runners as they'll still have an SDK-level
> >> >>> > > representation (though I don't think we should have an explicit
> goal
> >> >>> > > of feature parity for non-portable runners, e.g. multi-language
> isn't
> >> >>> > > happening, and hope that non-portable runners go away soon
> anyway).
> >> >>> > >
> >> >>> > > Now let's consider privacy annotations. To make things very
> concrete,
> >> >>> > > imagine a transform AverageSpendPerZipCode which takes as input
> (user,
> >> >>> > > zip, spend), all users unique, and returns (zip, avg(spend)). In
> >> >>> > > Python, this is GroupBy('zip').aggregate_field('spend',
> >> >>> > > MeanCombineFn()). This is not very privacy preserving to those
> users
> >> >>> > > who are the only (or one of a few) in a zip code. So we could
> define a
> >> >>> > > transform PrivacyPreservingAverageSpendPerZipCode as
> >> >>> > >
> >> >>> > > @ptransform_fn
> >> >>> > > def PrivacyPreservingAverageSpendPerZipCode(spend_per_user,
> threshold)
> >> >>> > > counts_per_zip = spend_per_user |
> >> >>> > > GroupBy('zip').aggregate_field('user', CountCombineFn())
> >> >>> > > spend_per_zip = spend_per_user |
> >> >>> > > GroupBy('zip').aggregate_field('spend', MeanCombineFn())
> >> >>> > > filtered = spend_per_zip | beam.Filter(
> >> >>> > > lambda x, counts: counts[x.zip] > threshold,
> >> >>> > > counts=AsMap(counts_per_zip))
> >> >>> > > return filtered
> >> >>> > >
> >> >>> > > We now have a composite that has privacy preserving properties
> (i.e.
> >> >>> > > the input may be quite sensitive, but the output is not,
> depending on
> >> >>> > > the value of threshold). What is interesting here is that it is
> only
> >> >>> > > the composite that has this property--no individual
> sub-transform is
> >> >>> > > itself privacy preserving. Furthermore, an optimizer may notice
> we're
> >> >>> > > doing aggregation on the same key twice and rewrite this using
> >> >>> > > (logically)
> >> >>> > >
> >> >>> > > GroupBy('zip').aggregate_field('user',
> >> >>> > > CountCombineFn()).aggregate_field('spend', MeanCombineFn())
> >> >>> > >
> >> >>> > > and then applying the filter, which is semantically equivalent
> and
> >> >>> > > satisfies the privacy annotations (and notably that does not
> even
> >> >>> > > require the optimizer to interpret the annotations, just pass
> them
> >> >>> > > on). To me, this implies that these annotations belong on the
> >> >>> > > composites, and *not* on the leaf nodes (where they would be
> >> >>> > > incorrect).
> >> >>> > >
> >> >>> > > I'll leave aside most questions of API until we figure out the
> model
> >> >>> > > semantics, but wanted to throw one possible idea out (though I
> am
> >> >>> > > ambivalent about it). Instead of attaching things to
> transforms, we
> >> >>> > > can just wrap transforms in composites that have no role other
> than
> >> >>> > > declaring information about their contents. E.g. we could have a
> >> >>> > > composite transform whose payload is simply an assertion of the
> >> >>> > > privacy (or resource?) properties of its inner structure. This
> would
> >> >>> > > be just as expressive as adding new properties to transforms
> >> >>> > > themselves (but would add an extra level of nesting, and make
> >> >>> > > respecting the precice nesting more important).
> >> >>> > >
> >> >>> > > On Tue, Nov 17, 2020 at 8:12 AM Robert Burke <
> rob...@frantil.com> wrote:
> >> >>> > > >
> >> >>> > > > +1 to discussing PCollection annotations on a separate
> thread. It would be confusing to mix them up.
> >> >>> > > >
> >> >>> > > > -----------
> >> >>> > > >
> >> >>> > > > The question around conflicts is interesting, but confusing
> to me. I don't think they exist in general. I keep coming back around to
> that it depends on the annotation and the purpose of composites.
> Optionality saves us here too.
> >> >>> > > >
> >> >>> > > > Composites are nothing without their internal hypergraph
> structure. Eventually it comes down to executing the leaf nodes. The
> alternative to executing the leaf nodes is when the composite represents a
> known transform and is replaced by the runner on submission time. Lets
> look at each.
> >> >>> > > >
> >> >>> > > > If there's a property that only exists on the leaf nodes,
> then it's not possible to bubble up that property to the composite in all
> cases. Afterall, it's not necessarily the case that a privacy preserving
> transform maintains the property for all output edges as not all such edges
> pass through the preserving transform.
> >> >>> > > >
> >> >>> > > > On the other hand, with memory or gpu recommendations, that
> might set a low bar on the composite level.
> >> >>> > > >
> >> >>> > > > But, composites (any transform really) can be runner
> replaced. I think it's fair to say that a runner replaced composite is not
> beholden to the annotations of the original leaf transforms, especially
> around physical requirements. The implementations are different. If a known
> composite at the composite level requires GPUs and it's known replacement
> doesn't, I'd posit that replacement was a choice the runner made since it
> can't provision machines with GPUs.
> >> >>> > > >
> >> >>> > > > But, crucially around privacy annotated transforms, a runner
> likely shouldn't replace a given subgraph that contains a privacy
> annotationed transform unless the replacements provide the same level of
> privacy. However, such replacements only happens with well known transforms
> with known properties anyway, so this can serve as an additional layer of
> validation for a runner aware of the properties.
> >> >>> > > >
> >> >>> > > > This brings me back to my position: that the notion of
> conflicts is very annotation dependant, and that defining them as optional
> is the most important feature to avoid issues. Conflicts don't exist as an
> inherent property of annotations on ptransform of the hypergraph structure.
> Am i wrong? No one has come up with an actual example of a conflict as far
> as i understand the thread.
> >> >>> > > >
> >> >>> > > > Even Reuven's original question is more about whether the
> runner is forced to look at leaf bodes rather than only looking at the
> composite. Assuming the composite isn't replaced, the runner needs to look
> at the leaf nodes regardless. And as discussed above there's no generalized
> semantics that fit for all kinds of annotations, once replacements are also
> considered.
> >> >>> > > >
> >> >>> > > > On Tue, Nov 17, 2020, 6:35 AM Ismaël Mejía <ieme...@gmail.com>
> wrote:
> >> >>> > > >>
> >> >>> > > >> +1 Nice to see there is finally interest on this.
> Annotations for
> >> >>> > > >> PTransforms make total sense!
> >> >>> > > >>
> >> >>> > > >> The semantics should be strictly optional for runners and
> correct
> >> >>> > > >> execution should not be affected by lack of support of any
> annotation.
> >> >>> > > >> We should however keep the set of annotations small.
> >> >>> > > >>
> >> >>> > > >> > PTransforms are hierarchical - namely a PTransform
> contains other PTransforms, and so on. Is the runner expected to resolve
> all annotations down to leaf nodes? What happens if that results in
> conflicting annotations?
> >> >>> > > >>
> >> >>> > > >> +1 to this question, This needs to be detailed.
> >> >>> > > >>
> >> >>> > > >> I am curious about how the end user APIs of this will look
> maybe in
> >> >>> > > >> Java or Python, just an extra method to inject a Map or via
> Java
> >> >>> > > >> annotations/Python decorators?
> >> >>> > > >>
> >> >>> > > >> We might prefer not to mix the concepts of annotations and
> >> >>> > > >> environments because this will limit the scope of
> annotations.
> >> >>> > > >> Annotations are different from environments because they
> serve a more
> >> >>> > > >> general idea: to express an intention and it is up to the
> runner to
> >> >>> > > >> choose the strategy to accomplish this, for example in the
> GPU
> >> >>> > > >> assignation case it could be to rewrite resource allocation
> via
> >> >>> > > >> Environments but it could also just delegate this to a
> resource
> >> >>> > > >> manager which is what we could do for example for GPU (or
> data
> >> >>> > > >> locality) cases on the Spark/Flink classic runners. If we
> tie this to
> >> >>> > > >> environments we will leave classic runners out of the loop
> for no
> >> >>> > > >> major reason and also not cover use cases not related to
> resource
> >> >>> > > >> allocation.
> >> >>> > > >>
> >> >>> > > >> I do not understand the use case to justify PCollection
> annotations
> >> >>> > > >> but to not mix this thread with them, would you be
> interested to
> >> >>> > > >> elaborate more about them in a different thread Jan?
> >> >>> > > >>
> >> >>> > > >> On Tue, Nov 17, 2020 at 2:28 AM Robert Bradshaw <
> rober...@google.com> wrote:
> >> >>> > > >> >
> >> >>> > > >> > I agree things like GPU, high-mem, etc. belong to the
> environment. If
> >> >>> > > >> > annotations are truly advisory, one can imagine merging
> environments
> >> >>> > > >> > by taking the union of annotations and still producing a
> correct
> >> >>> > > >> > pipeline. (This would mean that annotations would have to
> be a
> >> >>> > > >> > multi-map...)
> >> >>> > > >> >
> >> >>> > > >> > On the other hand, this doesn't seem to handle the case of
> privacy
> >> >>> > > >> > analysis, which could apply to composites without applying
> to any
> >> >>> > > >> > individual component, and don't really make sense as part
> of a
> >> >>> > > >> > fusion/execution story.
> >> >>> > > >> >
> >> >>> > > >> > On Mon, Nov 16, 2020 at 4:00 PM Robert Burke <
> rob...@frantil.com> wrote:
> >> >>> > > >> > >
> >> >>> > > >> > > That's good historical context.
> >> >>> > > >> > >
> >> >>> > > >> > > But then we'd still need to codify the annotation would
> need to be optional, and not affect correctness.
> >> >>> > > >> > >
> >> >>> > > >> > > Conflicts become easier to manage, (as environments with
> conflicting annotations simply don't get merged, and stay as distinct
> environments) but are still notionally annotation dependant. Do most
> runners handle environments so individually though?
> >> >>> > > >> > >
> >> >>> > > >> > > Reuven's question is a good one though. For the Go SDK,
> and the proposed implementation i saw, they only applied to leaf nodes.
> This is an artifact of how the Go SDK handles composites. Nothing stops it
> from being implemented on the composites Go has, but it didn't make sense
> otherwise. AFAICT Composites are generally for organizational convenience
> and not for functional aspects. Is this wrong? Afterall, does it make sense
> for environments to be on leaves and composites either? It's the same issue
> there.
> >> >>> > > >> > >
> >> >>> > > >> > >
> >> >>> > > >> > > On Mon, Nov 16, 2020, 3:45 PM Kenneth Knowles <
> k...@apache.org> wrote:
> >> >>> > > >> > >>
> >> >>> > > >> > >> I am +1 to the proposal but believe it should be moved
> to the Environment. I could be convinced otherwise, but would want to
> really understand the details.
> >> >>> > > >> > >>
> >> >>> > > >> > >> I think we haven't done a great job communicating the
> purpose of the Environment proto. It was explicitly created for this
> purpose.
> >> >>> > > >> > >>
> >> >>> > > >> > >> 1. It tells the runner things it needs to know to
> interpret the DoFn (or other UDF). So these are the existing proto fields
> like docker image (in the payload) and required artifacts that were staged.
> >> >>> > > >> > >> 2. It is also the place for additional requirements or
> hints like "high mem" or "GPU" etc.
> >> >>> > > >> > >>
> >> >>> > > >> > >> Every user function has an associated environment, and
> environments exist only for the purpose of executing user functions. In
> fact, Environment originated as inline requirements/attributes for a user
> function proto message and was separated just to make the proto smaller.
> >> >>> > > >> > >>
> >> >>> > > >> > >> A PTransform is an abstract concept for organizing the
> graph, not an executable thing. So a hint/capability/requirement on a
> PTransform only really makes sense as a scoping mechanism for applying a
> hint to a bunch of functions within a subgraph. This seems like a user
> interface concern and the SDK should own propagating the hints. If the hint
> truly applies to the whole PTransform and *not* the parts, then I am
> interested in learning about that.
> >> >>> > > >> > >>
> >> >>> > > >> > >> Kenn
> >> >>> > > >> > >>
> >> >>> > > >> > >> On Mon, Nov 16, 2020 at 10:54 AM Robert Burke <
> rob...@frantil.com> wrote:
> >> >>> > > >> > >>>
> >> >>> > > >> > >>> That's a good question.
> >> >>> > > >> > >>>
> >> >>> > > >> > >>> I think the main difference is a matter of scope.
> Annotations would apply to a PTransform while an environment applies to
> sets of transforms. A difference is the optional nature of the annotations
> they don't affect correctness. Runners don't need to do anything with them
> and still execute the pipeline correctly.
> >> >>> > > >> > >>>
> >> >>> > > >> > >>> Consider a privacy analysis on a pipeline graph. An
> annotation indicating that a transform provides a certain level of
> anonymization can be used in an analysis to determine if the downstream
> transforms are encountering raw data or not.
> >> >>> > > >> > >>>
> >> >>> > > >> > >>> From my understanding (which can be wrong)
> environments are rigid. Transforms in different environments can't be
> fused. "This is the python env", "this is the java env" can't be merged
> together. It's not clear to me that we have defined when environments are
> safely fuseable outside of equality. There's value in that simplicity.
> >> >>> > > >> > >>>
> >> >>> > > >> > >>> AFIACT environment has less to do with the machines a
> pipeline is executing on than it does about the kinds of SDK pipelines it
> understands and can execute.
> >> >>> > > >> > >>>
> >> >>> > > >> > >>>
> >> >>> > > >> > >>>
> >> >>> > > >> > >>> On Mon, Nov 16, 2020, 10:36 AM Chad Dombrova <
> chad...@gmail.com> wrote:
> >> >>> > > >> > >>>>>
> >> >>> > > >> > >>>>>
> >> >>> > > >> > >>>>> Another example of an optional annotation is marking
> a transform to run on secure hardware, or to give hints to
> profiling/dynamic analysis tools.
> >> >>> > > >> > >>>>
> >> >>> > > >> > >>>>
> >> >>> > > >> > >>>> There seems to be a lot of overlap between this idea
> and Environments. Can you talk about how you feel they may be different or
> related? For example, I could see annotations as a way of tagging
> transforms with an Environment, or I could see Environments becoming a
> specialized form of annotation.
> >> >>> > > >> > >>>>
> >> >>> > > >> > >>>> -chad
> >> >>> > > >> > >>>>
> >> >>> > >
>
