On Tue, Oct 29, 2019 at 4:20 PM Kenneth Knowles <k...@apache.org> wrote:
>
> Point (1) is compelling. Solutions to the "minus epsilon" seem a bit complex.
> On the other hand, an opaque and abstract Timestamp type (in each SDK) going
> forward seems like a Pretty Good Idea (tm). Would you really have to go
> floating point? Could you just have a distinguished representation for
> non-inclusive upper/lower bounds? These could be at the same reduced
> resolution as timestamps in element metadata, since that is all they are
> compared against.
If I were coming up with an abstract, opaque representation of
Timestamp (and Duration) for Beam, I would explicitly include the
"minus epsilon" concept. One could still do arithmetic with these.
This would make any conversion to standard datetime libraries lossy
though.
> Point (2) is also good, though it seems like something that could be cleverly
> engineered and/or we just provide one implementation and it is easy to make
> your own for finer granularity, since a WindowFn separately receives the
> Timestamp (here I'm pretending it is abstract and opaque and likely
> approximate) and the original element with whatever precision the original
> data included.
Yes, but I don't see how a generic WindowFn would reach into the
(arbitrary) element and pull out this original data. One of the
benefits of the Beam model is that the WindowFn does not have to
depend on the element type.
> Point (3) the model/runner owns the timestamp metadata so I feel fine about
> it being approximated as long as any original user data is still present. I
> don't recall seeing a compelling case where the timestamp metadata that the
> runner tracks and understands is required to be exactly the same as a user
> value (assuming users understand this distinction, which is another issue
> that I would separate from whether it is technically feasible).
As we provide the ability to designate user data as the runner
timestamp against which to window, and promote the runner timestamp
back to user data (people are going to want to get DateTime or Instant
objects out of it), it seems tricky to explain to users that one or
both of these operations may be lossy (and, in addition, I don't think
there's a consistently safe direction to round).
> The more I think about the very real problems you point out, the more I think
> that our backwards-incompatible move should be to our own abstract Timestamp
> type, putting the design decision behind a minimal interface. If we see a
> concrete design for that data type, we might be inspired how to support more
> possibilities.
>
> As for the rest of the speculation... moving to nanos immediately helps users
> so I am now +1 on just doing it, or moving ahead with an abstract data type
> under the assumption that it will basically be nanos under the hood.
If the fact that it's stored as nanos under the hood leaks out (and I
have trouble seeing how it won't) I'd lean towards just using them
directly (e.g. Java Instant) rather than wrapping it.
> Having a cleverly resolution-independent system is interesting and maybe
> extremely future proof but maybe preparing for a very distant future that may
> never come.
>
> Kenn
>
> On Fri, Oct 18, 2019 at 11:35 AM Robert Bradshaw <rober...@google.com> wrote:
>>
>> TL;DR: We should just settle on nanosecond precision ubiquitously for
>> timestamp/windowing in Beam.
>>
>>
>> Re-visiting this discussion in light of cross-language transforms and
>> runners, and trying to tighten up testing. I've spent some more time
>> thinking about how we could make these operations granularity-agnostic, but
>> just can't find a good solution. In particular, the sticklers seem to be:
>>
>> (1) Windows are half-open intervals, and the timestamp associated with a
>> window coming out of a GBK is (by default) as large as possible but must
>> live in that window. (Otherwise WindowInto + GBK + WindowInto would have the
>> unforunate effect of moving aggregate values into subsequent windows, which
>> is clearly not the intent.) In other words, the timestamp of a grouped value
>> is basically End(Window) - epsilon. Unless we choose a representation able
>> to encode "minus epsilon" we must agree on a granularity.
>>
>> (2) Unless we want to have multiple vairants of all our WindowFns (e.g.
>> FixedWindowMillis, FixedWindowMicros, FixedWindowNanos) we must agree on a
>> granularity with which to parameterize these well-known operations. There
>> are cases (e.g. side input window mapping, merging) where these Fns may be
>> used downstream in contexts other than where they are applied/defined.
>>
>> (3) Reification of the timestamp into user-visible data, and the other way
>> around, require a choice of precision to expose to the user. This means that
>> the timestamp is actual data, and truncating/rounding cannot be done
>> implicitly. Also round trip of reification and application of timestamps
>> should hopefully be idempotent no matter the SDK.
>>
>> The closest I've come is possibly parameterizing the timestamp type, where
>> encoding, decoding (including pulling the end out of a window?), comparison
>> (against each other and a watermark), "minus epsilon", etc could be UDFs.
>> Possibly we'd need the full set of arithmetic operations to implement
>> FixedWindows on an unknown timestamp type. Reification would simply be
>> dis-allowed (or return an opaque rather than SDK-native) type if the SDK did
>> not know that window type. The fact that one might need comparison between
>> timestamps of different types, or (lossless) coercion from one type to
>> another, means that timestamp types need to know about each other, or
>> another entity needs to know about the full cross-product, unless there is a
>> common base-type (at which point we might as well always choose that).
>>
>> An intermediate solution is to settle on floating (decimal) point
>> representation, plus a "minus-epsiloin" bit. It wouldn't quite solve the
>> mapping through SDK-native types (which could require rounding or errors or
>> a new opaque type, and few date librarys could faithfully expose the minus
>> epsilon part). It might also be more expensive (compute and storage), and
>> would not allow us to use the protofuf timestamp/duration fields (or any
>> standard date/time libraries).
>>
>> Unless we can come up with a clean solution to the issues above shortly, I
>> think we should fix a precision and move forward. If this makes sense to
>> everyone, then we can start talking about the specific choice of precision
>> and a migration path (possibly only for portability).
>>
>>
>> For reference, the manipulations we do on timestamps are:
>>
>> WindowInto: Timestamp -> Window
>> TimestampCombine: Window, [Timestamp] -> Timestamp
>> End(Window)
>> Min(Timestamps)
>> Max(Timestamps)
>> PastEndOfWindow: Watermark, Window -> {True, False}
>>
>> [SideInput]WindowMappingFn: Window -> Window
>> WindowInto(End(Window))
>>
>> GetTimestamp: Timestamp -> SDK Native Object
>> EmitAtTimestamp: SDK Native Object -> Timestamp
>>
>>
>>
>>
>>
>>
>> On Fri, May 10, 2019 at 1:33 PM Robert Bradshaw <rober...@google.com> wrote:
>>>
>>> On Thu, May 9, 2019 at 9:32 AM PM Kenneth Knowles <k...@apache.org> wrote:
>>>
>>> > From: Robert Bradshaw <rober...@google.com>
>>> > Date: Wed, May 8, 2019 at 3:00 PM
>>> > To: dev
>>> >
>>> >> From: Kenneth Knowles <k...@apache.org>
>>> >> Date: Wed, May 8, 2019 at 6:50 PM
>>> >> To: dev
>>> >>
>>> >> >> The end-of-window, for firing, can be approximate, but it seems it
>>> >> >> should be exact for timestamp assignment of the result (and similarly
>>> >> >> with the other timestamp combiners).
>>> >> >
>>> >> > I was thinking that the window itself should be stored as exact data,
>>> >> > while just the firing itself is approximated, since it already is,
>>> >> > because of watermarks and timers.
>>> >>
>>> >> I think this works where we can compare encoded windows, but some
>>> >> portable interpretation of windows is required for runner-side
>>> >> implementation of merging windows (for example).
>>> >
>>> > But in this case, you've recognized the URN of the WindowFn anyhow, so
>>> > you understand its windows. Remembering that IntervalWindow is just one
>>> > choice, and that windows themselves are totally user-defined and that
>>> > merging logic is completely arbitrary per WindowFn (we probably should
>>> > have some restrictions, but see
>>> > https://issues.apache.org/jira/browse/BEAM-654). So I file this use case
>>> > in the "runner knows everything about the WindowFn and Window type and
>>> > window encoding anyhow".
>>>
>>> Being able to merge common windows in the runner is just an
>>> optimization, but an important one (especially for bootstrapping
>>> SDKs). However, this is not just about runner to SDK, but SDK to SDK
>>> as well (where a user from one SDK may want to inspect the windows
>>> produced by another). Having MillisIntervalWindow,
>>> MicrosIntervalWindow, NanosIntervalWindow, etc. isn't a path that I
>>> think is worth going down.
>>>
>>> Yes, we need to solve the "extract the endpoint of an unknown encoded
>>> window" problem as well, possibly similar to what we do with length
>>> prefix coders, possibly a restriction on window encodings themselves.
>>>
>>> >> There may also be issues if windows (or timestamps) are assigned to a
>>> >> high precision in one SDK, then inspected/acted on in another SDK, and
>>> >> then passed back to the original SDK where the truncation would be
>>> >> visible.
>>> >
>>> > This is pretty interesting and complex. But again, a window is just data.
>>> > An SDK has to know how to deserialize it to operate on it. Unless we do
>>> > actually standardize some aspects of it. I don't believe BoundedWindow
>>> > encoding has a defined way to get the timestamp without decoding the
>>> > window, does it? I thought we had basically default to all
>>> > InternalWindows. But I am not following that closely.
>>> >
>>> >> > You raise a good point that min/max timestamp combiners require
>>> >> > actually understanding the higher-precision timestamp. I can think of
>>> >> > a couple things to do. One is the old "standardize all 3 or for
>>> >> > precisions we need" and the other is that combiners other than EOW
>>> >> > exist primarily to hold the watermark, and that hold does not require
>>> >> > the original precision. Still, neither of these is that satisfying.
>>> >>
>>> >> In the current model, the output timestamp is user-visible.
>>> >
>>> > But as long as the watermark hold is less, it is safe. It requires
>>> > knowing the coarse-precision lower bound of the timestamps of the input.
>>> > And there may be situations where you also want the coarse upper bound.
>>> > But you do know that these are at most one millisecond apart (assuming
>>> > the runner is in millis) so perhaps no storage overhead. But a lot of
>>> > complexity and chances for off by ones. And this is pretty hand-wavy.
>>>
>>> Yeah. A different SDK may (implicitly or explicitly) ask for the
>>> timestamp of the (transitive) output of a GBK, for which an
>>> approximation (either way) is undesirable.
>>>
>>> >> >> > A correction: Java *now* uses nanoseconds [1]. It uses the same
>>> >> >> > breakdown as proto (int64 seconds since epoch + int32 nanos within
>>> >> >> > second). It has legacy classes that use milliseconds, and Joda
>>> >> >> > itself now encourages moving back to Java's new Instant type.
>>> >> >> > Nanoseconds should complicate the arithmetic only for the one
>>> >> >> > person authoring the date library, which they have already done.
>>> >> >>
>>> >> >> The encoding and decoding need to be done in a language-consistent way
>>> >> >> as well.
>>> >> >
>>> >> > I honestly am not sure what you mean by "language-consistent" here.
>>> >>
>>> >> If we want to make reading and writing of timestamps, windows
>>> >> cross-language, we can't rely on language-specific libraries to do the
>>> >> encoding.
>>> >>
>>> >> >> Also, most date libraries don't division, etc. operators, so
>>> >> >> we have to do that as well. Not that it should be *that* hard.
>>> >> >
>>> >> > If the libraries dedicated to time handling haven't found it needful,
>>> >> > is there a specific reason you raise this? We do some simple math to
>>> >> > find the window things fall into; is that it?
>>> >>
>>> >> Yes. E.g.
>>> >>
>>> >> https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/windowing/FixedWindows.java#L77
>>> >>
>>> >> would be a lot messier if there were no mapping date libraries to raw
>>> >> ints that we can do arithmetic on. Writing this with the (seconds,
>>> >> nanos) representation is painful. But I suppose we'd only have to do
>>> >> it once per SDK.
>>> >
>>> >
>>> > Yea I think that arithmetic is not so bad. But this raises the issue of
>>> > writing a *generic* WindowFn where its idea of timestamp granularity (the
>>> > WindowFn owns the window type and encoding) may not match the user data
>>> > coming in. So you need to apply the approximation function to provide
>>> > type-correct input to the WindowFn. That's kind of exciting and weird and
>>> > perhaps unsolvable, except by choosing a concrete granularity.
>>> >
>>> > Kenn
>>> >
>>> >>
>>> >>
>>> >> >> >> It would also be really nice to clean up the infinite-future being
>>> >> >> >> the
>>> >> >> >> somewhat arbitrary max micros rounded to millis, and
>>> >> >> >> end-of-global-window being infinite-future minus 1 hour (IIRC),
>>> >> >> >> etc.
>>> >> >> >> as well as the ugly logic in Python to cope with millis-micros
>>> >> >> >> conversion.
>>> >> >> >
>>> >> >> > I actually don't have a problem with this. If you are trying to
>>> >> >> > keep the representation compact, not add bytes on top of instants,
>>> >> >> > then you just have to choose magic numbers, right?
>>> >> >>
>>> >> >> It's not about compactness, it's the (historically-derived?)
>>> >> >> arbitrariness of the numbers.
>>> >> >
>>> >> > What I mean is that the only reason to fit them into an integer at all
>>> >> > is compactness. Otherwise, you could use a proper disjoint union
>>> >> > representing your intent directly, and all fiddling goes away, like
>>> >> > `Timestamp ::= PosInf | NegInf | EndOfGlobalWindow |
>>> >> > ActualTime(Instant)`. It costs a couple of bits.
>>> >>
>>> >> The other cost is not being able to use standard libraries to
>>> >> represent all of your timestamps.
>>> >>
>>> >> >> For example, the bounds are chosen to
>>> >> >> fit within 64-bit mircos despite milliseconds being the "chosen"
>>> >> >> granularity, and care was taken that
>>> >> >>
>>> >> >> WindowInto(Global) | GBK | WindowInto(Minute) | GBK
>>> >> >>
>>> >> >> works, but
>>> >> >>
>>> >> >> WindowInto(Global) | GBK | WindowInto(Day) | GBK
>>> >> >>
>>> >> >> may produce elements with timestamps greater than MaxTimestamp.
>>> >> >>
>>> >> >> >
>>> >> >> > Kenn
>>> >> >> >
>>> >> >> > [1] https://docs.oracle.com/javase/8/docs/api/java/time/Instant.html
>>> >> >> >
>>> >> >> >>
>>> >> >> >> > On Wed, Apr 17, 2019 at 3:13 PM Robert Burke
>>> >> >> >> > <rob...@frantil.com> wrote:
>>> >> >> >> >>
>>> >> >> >> >> +1 for plan B. Nano second precision on windowing seems... a
>>> >> >> >> >> little much for a system that's aggregating data over time.
>>> >> >> >> >> Even for processing say particle super collider data, they'd
>>> >> >> >> >> get away with artificially increasing the granularity in batch
>>> >> >> >> >> settings.
>>> >> >> >> >>
>>> >> >> >> >> Now if they were streaming... they'd probably want femtoseconds
>>> >> >> >> >> anyway.
>>> >> >> >> >> The point is, we should see if users demand it before adding in
>>> >> >> >> >> the necessary work.
>>> >> >> >> >>
>>> >> >> >> >> On Wed, 17 Apr 2019 at 14:26, Chamikara Jayalath
>>> >> >> >> >> <chamik...@google.com> wrote:
>>> >> >> >> >>>
>>> >> >> >> >>> +1 for plan B as well. I think it's important to make
>>> >> >> >> >>> timestamp precision consistent now without introducing
>>> >> >> >> >>> surprising behaviors for existing users. But we should move
>>> >> >> >> >>> towards a higher granularity timestamp precision in the long
>>> >> >> >> >>> run to support use-cases that Beam users otherwise might miss
>>> >> >> >> >>> out (on a runner that supports such precision).
>>> >> >> >> >>>
>>> >> >> >> >>> - Cham
>>> >> >> >> >>>
>>> >> >> >> >>> On Wed, Apr 17, 2019 at 1:35 PM Lukasz Cwik <lc...@google.com>
>>> >> >> >> >>> wrote:
>>> >> >> >> >>>>
>>> >> >> >> >>>> I also like Plan B because in the cross language case, the
>>> >> >> >> >>>> pipeline would not work since every party (Runners & SDKs)
>>> >> >> >> >>>> would have to be aware of the new
>>> >> >> >> >>>> beam:coder:windowed_value:v2 coder. Plan A has the property
>>> >> >> >> >>>> where if the SDK/Runner wasn't updated then it may start
>>> >> >> >> >>>> truncating the timestamps unexpectedly.
>>> >> >> >> >>>>
>>> >> >> >> >>>> On Wed, Apr 17, 2019 at 1:24 PM Lukasz Cwik
>>> >> >> >> >>>> <lc...@google.com> wrote:
>>> >> >> >> >>>>>
>>> >> >> >> >>>>> Kenn, this discussion is about the precision of the
>>> >> >> >> >>>>> timestamp in the user data. As you had mentioned, Runners
>>> >> >> >> >>>>> need not have the same granularity of user data as long as
>>> >> >> >> >>>>> they correctly round the timestamp to guarantee that
>>> >> >> >> >>>>> triggers are executed correctly but the user data should
>>> >> >> >> >>>>> have the same precision across SDKs otherwise user data
>>> >> >> >> >>>>> timestamps will be truncated in cross language scenarios.
>>> >> >> >> >>>>>
>>> >> >> >> >>>>> Based on the systems that were listed, either microsecond or
>>> >> >> >> >>>>> nanosecond would make sense. The issue with changing the
>>> >> >> >> >>>>> precision is that all Beam runners except for possibly Beam
>>> >> >> >> >>>>> Python on Dataflow are using millisecond precision since
>>> >> >> >> >>>>> they are all using the same Java Runner windowing/trigger
>>> >> >> >> >>>>> logic.
>>> >> >> >> >>>>>
>>> >> >> >> >>>>> Plan A: Swap precision to nanosecond
>>> >> >> >> >>>>> 1) Change the Python SDK to only expose millisecond
>>> >> >> >> >>>>> precision timestamps (do now)
>>> >> >> >> >>>>> 2) Change the user data encoding to support nanosecond
>>> >> >> >> >>>>> precision (do now)
>>> >> >> >> >>>>> 3) Swap runner libraries to be nanosecond precision aware
>>> >> >> >> >>>>> updating all window/triggering logic (do later)
>>> >> >> >> >>>>> 4) Swap SDKs to expose nanosecond precision (do later)
>>> >> >> >> >>>>>
>>> >> >> >> >>>>> Plan B:
>>> >> >> >> >>>>> 1) Change the Python SDK to only expose millisecond
>>> >> >> >> >>>>> precision timestamps and keep the data encoding as is (do
>>> >> >> >> >>>>> now)
>>> >> >> >> >>>>> (We could add greater precision later to plan B by creating
>>> >> >> >> >>>>> a new version beam:coder:windowed_value:v2 which would be
>>> >> >> >> >>>>> nanosecond and would require runners to correctly perform an
>>> >> >> >> >>>>> internal conversions for windowing/triggering.)
>>> >> >> >> >>>>>
>>> >> >> >> >>>>> I think we should go with Plan B and when users request
>>> >> >> >> >>>>> greater precision we can make that an explicit effort. What
>>> >> >> >> >>>>> do people think?
>>> >> >> >> >>>>>
>>> >> >> >> >>>>>
>>> >> >> >> >>>>>
>>> >> >> >> >>>>> On Wed, Apr 17, 2019 at 5:43 AM Maximilian Michels
>>> >> >> >> >>>>> <m...@apache.org> wrote:
>>> >> >> >> >>>>>>
>>> >> >> >> >>>>>> Hi,
>>> >> >> >> >>>>>>
>>> >> >> >> >>>>>> Thanks for taking care of this issue in the Python SDK,
>>> >> >> >> >>>>>> Thomas!
>>> >> >> >> >>>>>>
>>> >> >> >> >>>>>> It would be nice to have a uniform precision for timestamps
>>> >> >> >> >>>>>> but, as Kenn
>>> >> >> >> >>>>>> pointed out, timestamps are extracted from systems that
>>> >> >> >> >>>>>> have different
>>> >> >> >> >>>>>> precision.
>>> >> >> >> >>>>>>
>>> >> >> >> >>>>>> To add to the list: Flink - milliseconds
>>> >> >> >> >>>>>>
>>> >> >> >> >>>>>> After all, it doesn't matter as long as there is sufficient
>>> >> >> >> >>>>>> precision
>>> >> >> >> >>>>>> and conversions are done correctly.
>>> >> >> >> >>>>>>
>>> >> >> >> >>>>>> I think we could improve the situation by at least adding a
>>> >> >> >> >>>>>> "milliseconds" constructor to the Python SDK's Timestamp.
>>> >> >> >> >>>>>>
>>> >> >> >> >>>>>> Cheers,
>>> >> >> >> >>>>>> Max
>>> >> >> >> >>>>>>
>>> >> >> >> >>>>>> On 17.04.19 04:13, Kenneth Knowles wrote:
>>> >> >> >> >>>>>> > I am not so sure this is a good idea. Here are some
>>> >> >> >> >>>>>> > systems and their
>>> >> >> >> >>>>>> > precision:
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > Arrow - microseconds
>>> >> >> >> >>>>>> > BigQuery - microseconds
>>> >> >> >> >>>>>> > New Java instant - nanoseconds
>>> >> >> >> >>>>>> > Firestore - microseconds
>>> >> >> >> >>>>>> > Protobuf - nanoseconds
>>> >> >> >> >>>>>> > Dataflow backend - microseconds
>>> >> >> >> >>>>>> > Postgresql - microseconds
>>> >> >> >> >>>>>> > Pubsub publish time - nanoseconds
>>> >> >> >> >>>>>> > MSSQL datetime2 - 100 nanoseconds (original datetime
>>> >> >> >> >>>>>> > about 3 millis)
>>> >> >> >> >>>>>> > Cassandra - milliseconds
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > IMO it is important to be able to treat any of these as a
>>> >> >> >> >>>>>> > Beam
>>> >> >> >> >>>>>> > timestamp, even though they aren't all streaming. Who
>>> >> >> >> >>>>>> > knows when we
>>> >> >> >> >>>>>> > might be ingesting a streamed changelog, or using them
>>> >> >> >> >>>>>> > for reprocessing
>>> >> >> >> >>>>>> > an archived stream. I think for this purpose we either
>>> >> >> >> >>>>>> > should
>>> >> >> >> >>>>>> > standardize on nanoseconds or make the runner's
>>> >> >> >> >>>>>> > resolution independent
>>> >> >> >> >>>>>> > of the data representation.
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > I've had some offline conversations about this. I think
>>> >> >> >> >>>>>> > we can have
>>> >> >> >> >>>>>> > higher-than-runner precision in the user data, and allow
>>> >> >> >> >>>>>> > WindowFns and
>>> >> >> >> >>>>>> > DoFns to operate on this higher-than-runner precision
>>> >> >> >> >>>>>> > data, and still
>>> >> >> >> >>>>>> > have consistent watermark treatment. Watermarks are just
>>> >> >> >> >>>>>> > bounds, after all.
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > Kenn
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > On Tue, Apr 16, 2019 at 6:48 PM Thomas Weise
>>> >> >> >> >>>>>> > <t...@apache.org
>>> >> >> >> >>>>>> > <mailto:t...@apache.org>> wrote:
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > The Python SDK currently uses timestamps in
>>> >> >> >> >>>>>> > microsecond resolution
>>> >> >> >> >>>>>> > while Java SDK, as most would probably expect, uses
>>> >> >> >> >>>>>> > milliseconds.
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > This causes a few difficulties with portability
>>> >> >> >> >>>>>> > (Python coders need
>>> >> >> >> >>>>>> > to convert to millis for WindowedValue and Timers,
>>> >> >> >> >>>>>> > which is related
>>> >> >> >> >>>>>> > to a bug I'm looking into:
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > https://issues.apache.org/jira/browse/BEAM-7035
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > As Luke pointed out, the issue was previously
>>> >> >> >> >>>>>> > discussed:
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > https://issues.apache.org/jira/browse/BEAM-1524
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > I'm not privy to the reasons why we decided to go
>>> >> >> >> >>>>>> > with micros in
>>> >> >> >> >>>>>> > first place, but would it be too big of a change or
>>> >> >> >> >>>>>> > impractical for
>>> >> >> >> >>>>>> > other reasons to switch Python SDK to millis before
>>> >> >> >> >>>>>> > it gets more users?
>>> >> >> >> >>>>>> >
>>> >> >> >> >>>>>> > Thanks,
>>> >> >> >> >>>>>> > Thomas
>>> >> >> >> >>>>>> >
