How to cache ResolveRequirementEnvMarkers to reduce execution time in Bazel pip.parse (Bzlmod)

[huyhoang8704]

Hi everyone,

I’m currently using Bazel with Bzlmod, integrating Python dependencies via pip.parse.

During every build, I consistently see the following step being executed:

Running ResolveRequirementEnvMarkers(~/.momo/bazel-cache/local/modextwd/ruclearles_python~~pip/requirements_with_markers.in.json)
This step takes around 20–30 seconds each time, even when:

• requirements.txt hasn’t changed
• The Python version and platform remain the same
• The Bazel cache is already warm

From what I understand, ResolveRequirementEnvMarkers is re-evaluating environment markers for Python dependencies, but it doesn’t seem to benefit from Bazel’s cache.

My questions:

• Is this step expected to always run on every build when using pip.parse with Bzlmod?
• Is there any supported way to cache or reuse the result of ResolveRequirementEnvMarkers?
• Are there recommended Bazel flags or configuration (e.g. repository cache, module extension cache, lock files, etc.) to avoid re-running this step?
• Would using pip.parse(..., requirements_lock = ...) or pre-generated lock files help here?
• Any guidance or best practices to reduce the runtime of this step would be greatly appreciated.

Thanks in advance!