Enhance MLflow receiver

[YuanTingHsieh]

Issue

Previously, if users did not explicitly specify a tracking_uri, MLflow would default to using ./mlruns, which is a local directory on the FL server. This made it difficult for users to access logged metrics and artifacts, as the default path was not exposed or retrievable outside the server environment.

Description

This PR introduces an enhancement to set a more accessible default tracking_uri when none is provided by the user. Specifically, the default is now set to:

file://[workspace]/[job_id]/mlflow

This change enables users to retrieve the logged metrics and artifacts using the FlareAPI, as they are stored in a job-specific, accessible path within the workspace.

Notes

• This PR depends on Enhance recipe experiment tracking #3655.
• Ensures MLflow logs are stored in a consistent, retrievable location tied to the job and workspace.

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Quick tests passed locally by running ./runtest.sh.
• In-line docstrings updated.
• Documentation updated.

[Copilot]

Pull Request Overview

This PR enhances the MLflow receiver to provide a more accessible default tracking URI when none is explicitly configured. The change addresses the issue where MLflow previously defaulted to a local ./mlruns directory that was difficult for users to access outside the server environment.

• Sets default tracking URI to file://[workspace]/[job_id]/mlflow for better accessibility
• Updates run naming to include job name for improved identification
• Updates documentation to reflect workspace structure changes

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
nvflare/app_opt/tracking/mlflow/mlflow_receiver.py	Implements new default tracking URI logic and enhances run naming with job information
nvflare/app_opt/tracking/tb/tb_receiver.py	Updates documentation to reflect new workspace structure terminology

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