Refactor private attributes in Pydantic models to use PrivateAttr

[coderabbitai]

Description

In Pydantic v2, private attributes (those starting with underscore) should be declared using PrivateAttr() for stability and to follow the official API. While bare annotations like _attr: Type | None = None may work incidentally, they are not part of the guaranteed Pydantic API and can break with minor version updates.

Background

This issue was identified during review of PR #799:

• PR: Add support for running vLLM #799
• Comment: Add support for running vLLM #799 (comment)

Affected Files

The following files contain Pydantic models with private attributes that should be refactored to use PrivateAttr:

Workloads (19 files)

1. src/cloudai/workloads/vllm/vllm.py - _docker_image, _hf_model
2. src/cloudai/workloads/ucc_test/ucc.py - _docker_image
3. src/cloudai/workloads/slurm_container/slurm_container.py - _docker_image
4. src/cloudai/workloads/nixl_perftest/nixl_perftest.py - _docker_image
5. src/cloudai/workloads/osu_bench/osu_bench.py - _osu_image
6. src/cloudai/workloads/triton_inference/triton_inference.py - _server_image, _client_image
7. src/cloudai/workloads/nemo_run/nemo_run.py - _docker_image
8. src/cloudai/workloads/nemo_launcher/nemo_launcher.py - _docker_image, _python_executable
9. src/cloudai/workloads/nixl_kvbench/nixl_kvbench.py - _docker_image
10. src/cloudai/workloads/nixl_bench/nixl_bench.py - _nixl_image
11. src/cloudai/workloads/nccl_test/nccl.py - _docker_image
12. src/cloudai/workloads/jax_toolbox/nemotron.py - _docker_image
13. src/cloudai/workloads/jax_toolbox/grok.py - _docker_image
14. src/cloudai/workloads/jax_toolbox/gpt.py - _docker_image
15. src/cloudai/workloads/megatron_run/megatron_run.py - _docker_image
16. src/cloudai/workloads/deepep/deepep.py - _docker_image
17. src/cloudai/workloads/chakra_replay/chakra_replay.py - _docker_image
18. src/cloudai/workloads/ddlb/ddlb.py - _docker_image
19. src/cloudai/workloads/megatron_bridge/megatron_bridge.py - _docker_image, _python_executable, _megatron_bridge_repo
20. src/cloudai/workloads/ai_dynamo/ai_dynamo.py - _docker_image, _hf_model

Systems (1 file)

21. src/cloudai/systems/kubernetes/kubernetes_system.py - _core_v1, _batch_v1, _custom_objects_api, _genai_perf_completed

Recommended Changes

For each affected file:

1. Add PrivateAttr to the pydantic imports:

   from pydantic import Field, PrivateAttr

2. Replace bare annotations with PrivateAttr:

   # Before
   _docker_image: DockerImage | None = None
   
   # After
   _docker_image: DockerImage | None = PrivateAttr(default=None)

Good Example

src/cloudai/systems/runai/runai_system.py already follows this pattern correctly:

from pydantic import Field, PrivateAttr

class RunAISystem(KubernetesSystem):
    _api_client: Optional[RunAIRestClient] = PrivateAttr(default=None)

Note

src/cloudai/_core/installables.py uses dataclass field(), not Pydantic, so it doesn't need to be changed.

References

• Pydantic v2 Private Attributes Documentation: https://docs.pydantic.dev/latest/concepts/models/#private-model-attributes