[Go SDK] Rewrite dot runner to generate DOT from portable pipeline proto

[YousufFFFF]

Fixes #27508

This change rewrites the Go SDK dot runner to generate the DOT graph from the portable pipeline proto representation instead of relying on Go SDK internal graph structures.

By basing DOT generation on the portable pipeline model:

• Cross-language pipelines can now be rendered correctly.
• The implementation aligns with the portable runner architecture.
• It enables future reuse in Prism Runner and other portable tooling.

The current implementation focuses on rendering leaf transforms (composites are skipped explicitly), keeping the traversal simple while leaving room for future refinement of composite expansion strategies.

[gemini-code-assist]

Summary of Changes

Hello @YousufFFFF, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refactors the Go SDK's DOT graph generation mechanism. Instead of relying on internal Go SDK graph structures, the system now processes the portable pipeline protocol buffer representation to create DOT graphs. This fundamental shift enhances compatibility with cross-language pipelines and aligns the Go SDK with the broader portable runner architecture, paving the way for more integrated and reusable tooling.

Highlights

• Portable Pipeline Proto Integration: The Go SDK dot runner has been rewritten to generate DOT graphs directly from the portable pipeline protocol buffer representation.
• Cross-Language Compatibility: This change enables the correct rendering of cross-language pipelines in DOT format.
• Architectural Alignment: The implementation now aligns with the portable runner architecture, improving consistency and maintainability.
• Future Reusability: The new approach facilitates future reuse in tools like Prism Runner and other portable tooling.

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Changelog

• sdks/go/pkg/beam/runners/dot/dot.go
  • Replaced the dotlib import with graphx and added the fmt package.
  • Modified the Execute function to marshal pipeline edges into a portable protocol buffer representation using graphx.Marshal.
  • Implemented custom DOT graph generation logic by iterating over portable pipeline components and transforms.
  • Removed the previous reliance on dotlib.Render for DOT graph creation.
  • Added logic to build consumer relationships between PCollections and transforms, correctly handling and skipping composite transforms for accurate graph representation.

Activity

• No specific activity (comments, reviews, or progress updates) was provided in the context.

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[YousufFFFF]

Hi @mohamedawnallah!
CI checks are green and the implementation is complete.
Would appreciate your review when you have time.
Thanks!

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[YousufFFFF]

Hi @lostluck !

I’ve pushed updates to align the implementation more closely with the portable pipeline proto.
The DOT generation now operates directly on pipeline.GetComponents() and skips composite transforms explicitly, rather than relying on the previous internal graph utilities.
This keeps the implementation simple for now and leaves room to evolve the composite expansion strategy later based on further discussion.
I’d really appreciate your feedback when you have time.

[YousufFFFF]

R: @lostluck

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[mohamedawnallah]

Thanks @YousufFFFF for the PR! Left some comments.

[lostluck]

I agree with all of Mohamed's comments so far.

In particular, the one about simply just rewriting this to use bespoke code instead of the package.

As a first pass, add a few simple test cases that check the returned output. This is just good practice when doing a refactoring to make sure that some things are working at least as good as they were before. This is not a high bar, at least, due to not having any tests in the first place! Even just a 3-4 very basic pipelines as a smoke test would go a long way.

This dot runner is very old, so it is unfortunate that it was authored without tests, since it was actively being used to look at pipeline shapes.

---

Also, do take a look at the python "render" runner for inspiration, which also creates dot representations.

beam/sdks/python/apache_beam/runners/render.py

Line 135 in 9ee4fe6

class PipelineRenderer:

(Admittedly, having done a different python -> go conversion for prism's Fusion handling, the python handling is very Set Theory based rather than graph based, so it can take a moment to grasp what it's doing.)

[YousufFFFF]

Thank you @lostluck and @mohamedawnallah for the detailed review and guidance.

Based on the feedback, I’ve made the following updates:

• Removed the unused core/util/dot dependency.
• Verified there are no remaining usages in the Go SDK.
• Marked core/util/dot as Deprecated to discourage future use.
• Removed the redundant composite consumer check.
• Added deterministic topological sorting of transforms to ensure stable DOT emission.
• Added a basic deterministic output test for the DOT runner.

I also reviewed the Python render runner for reference and will keep alignment considerations in mind for future improvements while keeping this PR focused.

Appreciate the thoughtful suggestions, they helped improve clarity and maintainability.

[YousufFFFF]

I agree with all of Mohamed's comments so far.

In particular, the one about simply just rewriting this to use bespoke code instead of the package.

As a first pass, add a few simple test cases that check the returned output. This is just good practice when doing a refactoring to make sure that some things are working at least as good as they were before. This is not a high bar, at least, due to not having any tests in the first place! Even just a 3-4 very basic pipelines as a smoke test would go a long way.

This dot runner is very old, so it is unfortunate that it was authored without tests, since it was actively being used to look at pipeline shapes.

Also, do take a look at the python "render" runner for inspiration, which also creates dot representations.

beam/sdks/python/apache_beam/runners/render.py

Line 135 in 9ee4fe6

class PipelineRenderer:

(Admittedly, having done a different python -> go conversion for prism's Fusion handling, the python handling is very Set Theory based rather than graph based, so it can take a moment to grasp what it's doing.)

Thanks @lostluck - I’ll take a look at the Python render runner for reference.

That’s a good suggestion, especially since it already handles DOT generation in a more structured way. I’ll review its approach and see if there are any patterns or simplifications we can adopt here while keeping the Go implementation idiomatic.

Appreciate the pointer 👍