Thank you for explaining the details Robert! I do have 1 more question: is there a way in beam that allows triggering after n events arrived at the gbk step from previous parts of a pipeline? because afterCount() trigger for gbk is per-key, then it cannot be used here right?
On Mon, Aug 17, 2020 at 3:22 PM Robert Bradshaw <[email protected]> wrote: > Yeah, this is another subtlety. There's a notion of "window garbage > collection" that's distinct from "window closing." Garbage collection > happens regardless of whether the trigger was set iff the window is > non-empty when the watermark + allowed lateness exceeds the end of > window. (Well, there's a flag to control this behavior.) This has > changed over time and I think you've uncovered a bug that the two SDKs > are not consistent here. > > On Mon, Aug 17, 2020 at 2:29 PM Leiyi Zhang <[email protected]> wrote: > > > > is it just for the python sdk or for both python and java sdk? > > seems like java sdk will output result even if there are less than 3 > elements per key. > > > > On Mon, Aug 17, 2020 at 2:20 PM Robert Bradshaw <[email protected]> > wrote: > >> > >> Yes, GBK is non-determanistic in the face of triggers as well. All > >> triggers are per-key, evaluated independently for each key, so it'd be > >> "do I have at least 3 results for this key." > >> > >> On Mon, Aug 17, 2020 at 2:08 PM Leiyi Zhang <[email protected]> wrote: > >> > > >> > Thank you very much for the reply, > >> > Is the result of gbk non-deterministic as well? between "do I have at > least 3 results PER KEY" vs "do I have at least 3 incoming events before I > trigger GBK" > >> > > >> > On Mon, Aug 17, 2020 at 1:39 PM Robert Bradshaw <[email protected]> > wrote: > >> >> > >> >> Triggers in beam are non-determanistic; both behaviors are acceptable > >> >> (especially for batch mode). In practice, production runners evaluate > >> >> triggers (e.g. in this case "do I have at least two elements") > whenver > >> >> a new batch of data comes in (for the Python direct runner, in batch > >> >> mode, all the data comes in at once). To have more control over this > >> >> you can use TestPipeline, which will attempt to fire triggers as > >> >> eagerly as possible. > >> >> > >> >> On Mon, Aug 17, 2020 at 1:16 PM Leiyi Zhang <[email protected]> > wrote: > >> >> > > >> >> > for GBK wtih AfterCount(3), java sdk results in this and python > sdk results in this > >> >> > > >> >> > for global count with aftercount(2), java sdk results in 2 2 2 2 > and python sdk results in 8. > >> >> > > >> >> > On Mon, Aug 17, 2020 at 12:40 PM Robert Bradshaw < > [email protected]> wrote: > >> >> >> > >> >> >> What results do you get in each? > >> >> >> > >> >> >> On Mon, Aug 17, 2020 at 11:55 AM Leiyi Zhang <[email protected]> > wrote: > >> >> >> > > >> >> >> > Hi everyone! > >> >> >> > I noticed that the behavior of AfterCount() trigger seems to be > different between python sdk and the java one, so I created a few tests to > show the difference, but in general I think the python sdk will buffer on > result instead of input elements. > >> >> >> > > >> >> >> > What do you guys think? > >> >> >> > > >> >> >> > and here are the tests. I ran them in batch mode. > >> >> >> > > >> >> >> > Sincerely, > >> >> >> > Leiyi >
