[BLD]: use cache mount in Rust Dockerfile

[codetheweb]

Description of changes

Uses Docker cache mounts to cache Rust artifacts instead of layer caching. A cache mount persists across docker builds and is not stored as a layer in the image. Using a cache mount is better because:

• if a dependency changes, it does not require all dependencies to be rebuilt
• only changed Chroma code will be rebuilt

I tested the savings by performing an incremental build (with target compaction_service) after touching a file in the worker crate.

Before:

• debug: 35s
• release: 1m8s

After:

• debug: 14s
• release: 58s

It doesn't seem to speed up release builds as much as I was hoping, but a 2x reduction in debug build time is a nice win. Also makes the Dockerfile easier to read. Savings may be more pronounced when running multiple builds concurrently (e.g. the query and compactor service inside Tilt).

Test plan

How are these changes tested?

Built debug & release images locally.

Documentation Changes

Are all docstrings for user-facing APIs updated if required? Do we need to make documentation changes in the docs repository?

n/a

[github-actions]

Reviewer Checklist

Please leverage this checklist to ensure your code review is thorough before approving

Testing, Bugs, Errors, Logs, Documentation

• Can you think of any use case in which the code does not behave as intended? Have they been tested?
• Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• If appropriate, are there adequate property based tests?
• If appropriate, are there adequate unit tests?
• Should any logging, debugging, tracing information be added or removed?
• Are error messages user-friendly?
• Have all documentation changes needed been made?
• Have all non-obvious changes been commented?

System Compatibility

• Are there any potential impacts on other parts of the system or backward compatibility?
• Does this change intersect with any items on our roadmap, and if so, is there a plan for fitting them together?

Quality

• Is this code of a unexpectedly high quality (Readability, Modularity, Intuitiveness)

[HammadB]

This makes sense to me. Does sharing=locked mean that query/compaction can't build concurrently in tilt?

[codetheweb]

This makes sense to me. Does sharing=locked mean that query/compaction can't build concurrently in tilt?

Yes, but this is actually a feature, not a bug. :) Building the query and compaction services concurrently in Tilt wastes a lot of compute since they share 95%+ of their dependencies/code. So overall it should be faster now since one will build and then the other can used the cached result to finish building its delta.