Yup! : ) - I think On Tue, Apr 9, 2019 at 3:52 PM Brian Hulette <bhule...@google.com> wrote:
> Are these the blog posts? > > https://beam.apache.org/blog/2017/02/13/stateful-processing.html > https://beam.apache.org/blog/2017/08/28/timely-processing.html > > On Tue, Apr 9, 2019 at 3:41 PM Pablo Estrada <pabl...@google.com> wrote: > >> soooounds good. Thanks guys <3 >> >> On Tue, Apr 9, 2019 at 3:19 PM Lukasz Cwik <lc...@google.com> wrote: >> >>> UnboundedSources and SplittableDoFns report watermarks which the runner >>> uses to compute how much the watermark could advance if it processed some >>> outstanding work. But it is always upto the runner to choose when the >>> watermark advances. The runner could process each work item in watermark >>> priority order and advance the watermark in small increments or could >>> process many work items and then advance the watermark a lot. (Note that >>> the BoundedSources API doesn't allow for reporting the watermark and it >>> starts at Beam's concept of START OF TIME and advances in one step to >>> Beam's concept of END OF TIME). >>> >>> You might be able to write what you want with an event based timer. Kenn >>> wrote (2?) blog posts on state and timers that have some pretty good >>> explanations and examples. >>> >>> On Tue, Apr 9, 2019 at 2:27 PM Pablo Estrada <pabl...@google.com> wrote: >>> >>>> hi Luke, >>>> thanks for the prompt reply: ) >>>> >>>> That makes sense. I think I'll go back to my cave to read a bunch about >>>> streaming. : ) >>>> >>>> I was looking for this to try to write a sequence generator for Python >>>> in streaming, and I was trying to debug what was going on. I was trying to >>>> allow the DoFn to receive a watermark reported by the upstream source. (... >>>> does that answer "which watermark?"... I am not sure that it does... but >>>> maybe..). >>>> >>>> Do you think it's a reasonable use case for DoFns to know what the >>>> upstream watermark is? >>>> I hope that makes at least a some sense... : ) >>>> >>>> If it doesn't make sense, feel free to ignore, and I'll go do my >>>> readings. >>>> Thanks! >>>> -P. >>>> >>>> On Tue, Apr 9, 2019 at 1:44 PM Lukasz Cwik <lc...@google.com> wrote: >>>> >>>>> WatermarkReporterParam is about reporting the watermark. The main >>>>> usecase is for SplittableDoFns to be able to report the data watermark. >>>>> >>>>> The watermark is per input and output of a DoFn. Also each bundle >>>>> being processed has its local watermarks while the runner computes the >>>>> global watermark. The runners watermark could be per key, or key range or >>>>> global across all keys. >>>>> >>>>> There is no runner agnostic way to read the watermark today. Is there >>>>> a usecase you are targeting that would help from having access to the >>>>> watermark (also, which watermark?)? >>>>> >>>>> >>>>> On Tue, Apr 9, 2019 at 1:28 PM Pablo Estrada <pabl...@google.com> >>>>> wrote: >>>>> >>>>>> I am experimenting with state / timers in Python. As I look at the >>>>>> DoFnProcessParams[1], I see that it's possible for a DoFn to receive >>>>>> several arguments (e.g. Timers, Side Inputs, etc). Also the Watermark via >>>>>> WatermarkReporterParam. >>>>>> >>>>>> I see that this parameter is not handled by runners when filling up >>>>>> the arguments for a DoFn[2][3]. So, as far as I can tell, DoFns are not >>>>>> currently able to get the watermark. >>>>>> >>>>>> Is this a bug, or is it intentional? Perhaps there's another way to >>>>>> find out the watermark for a DoFn? >>>>>> >>>>>> Best >>>>>> -P. >>>>>> >>>>>> [1] >>>>>> https://github.com/apache/beam/blob/master/sdks/python/apache_beam/transforms/core.py#L381-L390 >>>>>> >>>>>> [2] >>>>>> https://github.com/apache/beam/blob/master/sdks/python/apache_beam/runners/common.py#L477-L488 >>>>>> [3] >>>>>> https://github.com/apache/beam/blob/master/sdks/python/apache_beam/runners/common.py#L605-L620 >>>>>> >>>>>
