# mlflow
pip install git+https://github.com/mlflow/mlflow.git@refs/pull/18542/merge
# mlflow-skinny
pip install git+https://github.com/mlflow/mlflow.git@refs/pull/18542/merge#subdirectory=libs/skinny

%sh curl -LsSf https://raw.githubusercontent.com/mlflow/mlflow/HEAD/dev/install-skinny.sh | sh -s pull/18542/merge

Related Issues/PRs

Fix #18541

What changes are proposed in this pull request?

1. Environment Variable (mlflow/environment_variables.py)
   Added MLFLOW_S3_BUCKET_OWNER environment variable to specify the expected AWS account ID that owns the S3 bucket. This is optional and backward compatible - when not set, the system behaves as before.
2. S3 Artifact Repository (mlflow/store/artifact/s3_artifact_repo.py)
   • Added _bucket_owner attribute initialized from the environment variable
   • Updated all S3 API calls to include ExpectedBucketOwner parameter when configured:
     • upload_file (single file uploads)
     • download_file (file downloads)
     • list_objects_v2 (listing artifacts)
     • delete_objects (deleting artifacts)
     • create_multipart_upload (multipart upload initiation)
     • complete_multipart_upload (multipart upload completion)
     • abort_multipart_upload (multipart upload abortion)
     • generate_presigned_url (presigned URL generation)
3. Optimized S3 Artifact Repository (mlflow/store/artifact/optimized_s3_artifact_repo.py)
   • Applied the same bucket ownership checks to all S3 operations
   • Updated head_bucket, upload_file, download_file, list_objects_v2, delete_objects, multipart upload operations, and presigned URL generation
4. Tests (tests/store/artifact/test_s3_artifact_repo.py)
   • Bucket ownership verification with environment variable set
   • Backward compatibility when environment variable is not set
   • Bucket takeover scenario simulation
   • List artifacts with bucket owner
   • Multipart upload with bucket owner
   • Delete artifacts with bucket owner

How is this PR tested?

• Existing unit/integration tests
• New unit/integration tests
• Manual tests

Does this PR require documentation update?

• [] No. You can skip the rest of this section.
• Yes. I've updated:
  • Examples
  • API references
  • Instructions

Release Notes

Is this a user-facing change?

• No. You can skip the rest of this section.
• Yes. Give a description of this change to be included in the release notes for MLflow users.

What component(s), interfaces, languages, and integrations does this PR affect?

Components

• area/tracking: Tracking Service, tracking client APIs, autologging
• area/models: MLmodel format, model serialization/deserialization, flavors
• area/model-registry: Model Registry service, APIs, and the fluent client calls for Model Registry
• area/scoring: MLflow Model server, model deployment tools, Spark UDFs
• area/evaluation: MLflow model evaluation features, evaluation metrics, and evaluation workflows
• area/gateway: MLflow AI Gateway client APIs, server, and third-party integrations
• area/prompts: MLflow prompt engineering features, prompt templates, and prompt management
• area/tracing: MLflow Tracing features, tracing APIs, and LLM tracing functionality
• area/projects: MLproject format, project running backends
• area/uiux: Front-end, user experience, plotting, JavaScript, JavaScript dev server
• area/build: Build and test infrastructure for MLflow
• area/docs: MLflow documentation pages

How should the PR be classified in the release notes? Choose one:

• rn/none - No description will be included. The PR will be mentioned only by the PR number in the "Small Bugfixes and Documentation Updates" section
• rn/breaking-change - The PR will be mentioned in the "Breaking Changes" section
• rn/feature - A new user-facing feature worth mentioning in the release notes
• rn/bug-fix - A user-facing bug fix worth mentioning in the release notes
• rn/documentation - A user-facing documentation change worth mentioning in the release notes

Should this PR be included in the next patch release?

Yes should be selected for bug fixes, documentation updates, and other small changes. No should be selected for new features and larger changes. If you're unsure about the release classification of this PR, leave this unchecked to let the maintainers decide.

• Yes (this PR will be cherry-picked and included in the next patch release)
• No (this PR will be included in the next minor release)