[#31438] Non-processing time triggers pass w/accumulation.

[lostluck]

• Effectively makes all aggregation transforms (AKA, GBKs) stateful.
• Adds all non-processing time derived triggers.
• Adds support for Accumulation mode.
• Adds computation of panes for the triggered aggregation results.
• Handles trigger edge case WRT Lifted combines and ElementCount triggers by disabling lifting when one is detected.
• Added some of the Go trigger tests to the engine_test.go file, to maintain coverage.
  • Note, the Go trigger tests are not canonical as the Go SDK has issues regarding panes, largely due to not having any runner that would support testing them. (see [Bug]: PaneInfo not populated in Go SDK #31153)(until prism).

Important notes: Does not support processing time triggers, or triggered side inputs or triggers against merging windows at this PR. Those will be supported at a later PR.

Blocks submission of Processing Time triggers at this time.

Increases the number of Java Validates Runner tests that pass from 325 to 336.

Part of #31438.

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[jrmccluskey]

assign to next reviewer

[lostluck]

R: @kennknowles @damccorm

As much as I'd love for Jack to look at this as well, he's doing the release and is busy enough.

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[kennknowles]

I took a quick pass and concluded that I will need some time. This one goes more into Prism details that I am not familiar with than the last one. It might be good for this to be a sit-down review with someone that you want to education about Prism's codebase.

[lostluck]

You're not wrong, but at this point there's unlikely to be a specific person to get this education, due to circumstances.

For broad strokes of how it works, it is why I wrote the deep dive, which will need an adjustment for the side channel injected bundles.

https://github.com/apache/beam/blob/master/sdks/go/pkg/beam/runners/prism/internal/README.md

[damccorm]

This mostly lgtm - I had some minor questions/comments

[lostluck]

Changes made. Also added the final "gate" WRT Stateful triggers with merging windows.

[damccorm]

Thanks - LGTM once checks pass

[lostluck]

Thanks for the review!

At this stage the next best move is to separate the different stage types, now that there's clarity in how each needs to function. It's fine when there are two different kinds (stateful and not stateful), but aggregation adds sufficient complexity that this won't be as maintainable without much care and reading to know which cyclomatic clause you're dealing with.