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Fix start_trace compatibility with old mlflow clients#19183

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B-Step62 merged 7 commits intomlflow:masterfrom
serena-ruan:fix_sql_trace_tag
Dec 4, 2025
Merged

Fix start_trace compatibility with old mlflow clients#19183
B-Step62 merged 7 commits intomlflow:masterfrom
serena-ruan:fix_sql_trace_tag

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@serena-ruan serena-ruan commented Dec 3, 2025

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Install mlflow from this PR

# mlflow
pip install git+https://github.com/mlflow/mlflow.git@refs/pull/19183/merge
# mlflow-skinny
pip install git+https://github.com/mlflow/mlflow.git@refs/pull/19183/merge#subdirectory=libs/skinny

For Databricks, use the following command:

%sh curl -LsSf https://raw.githubusercontent.com/mlflow/mlflow/HEAD/dev/install-skinny.sh | sh -s pull/19183/merge

Related Issues/PRs

#xxx

What changes are proposed in this pull request?

In old mlflow clients traces are stored in artifact storage, but it still invokes 'start_trace' call. However the SPANS_LOCATION tag is added, which decides where to load the spans. As a result, this causes an issue with newer mlflow server + old mlflow clients, where traces are stored in artifact repository but trying to be loaded from span table.

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.

What is a minor/patch release?
  • Minor release: a release that increments the second part of the version number (e.g., 1.2.0 -> 1.3.0).
    Bug fixes, doc updates and new features usually go into minor releases.
  • Patch release: a release that increments the third part of the version number (e.g., 1.2.0 -> 1.2.1).
    Bug fixes and doc updates usually go into patch releases.
  • 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)

Signed-off-by: Serena Ruan <serena.rxy@gmail.com>
@github-actions github-actions bot added v3.7.0 rn/none List under Small Changes in Changelogs. labels Dec 3, 2025
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github-actions bot commented Dec 3, 2025

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Signed-off-by: Serena Ruan <serena.rxy@gmail.com>
Signed-off-by: Serena Ruan <serena.rxy@gmail.com>
Copilot AI review requested due to automatic review settings December 4, 2025 02:51

@pytest.mark.skipif(
mlflow.get_tracking_uri().startswith("mysql"),
reason="MySQL does not support concurrent log_spans calls for now",
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This test fails on mysql with below error:

sqlalchemy.exc.OperationalError: (MySQLdb.OperationalError) (1213, 'Deadlock found when trying to get lock; try restarting transaction')
[SQL: UPDATE trace_info SET timestamp_ms=CASE WHEN (trace_info.timestamp_ms > %s) THEN %s ELSE trace_info.timestamp_ms END, execution_time_ms=(CASE WHEN (trace_info.timestamp_ms + trace_info.execution_time_ms > %s) THEN trace_info.timestamp_ms + trace_info.execution_time_ms ELSE %s END - CASE WHEN (trace_info.timestamp_ms > %s) THEN %s ELSE trace_info.timestamp_ms END) WHERE trace_info.request_id = %s]
[parameters: (1000, 1000, 2000, 2000, 1000, 1000, 'tr-46617ca3256749c7a5859266ad843913')]

But it's not related to the current change, but because of session.query(SqlTraceInfo).filter(SqlTraceInfo.request_id == trace_id).update call. I'm skipping this test in mysql for now, but we need to fix this issue separately.
Repro command:

uv run docker compose --project-directory tests/db run --rm --no-TTY mlflow-mysql pytest tests/store/tracking/test_sqlalchemy_store.py::test_concurrent_log_spans_spans_location_tag

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Do we plan to fix this by 3.7?

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Pull request overview

This PR fixes a compatibility issue between newer MLflow servers and older MLflow clients for trace management. The issue occurred because old clients store traces in artifact storage but still invoke start_trace, while the new server was automatically adding a SPANS_LOCATION tag, causing traces to be incorrectly loaded from the span table instead of artifact storage.

Key changes:

  • Remove automatic SPANS_LOCATION tag creation in start_trace() to support old clients that store spans in artifact storage
  • Add logic to preserve the SPANS_LOCATION tag when it's set by log_spans() for new clients
  • Update log_spans() to set the SPANS_LOCATION tag when spans are stored in the tracking database

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File Description
mlflow/store/tracking/sqlalchemy_store.py Removed automatic SPANS_LOCATION tag in start_trace() and added logic to preserve it if set by log_spans(), plus added tag update in log_spans()
tests/store/tracking/test_sqlalchemy_store.py Updated existing tests to remove SPANS_LOCATION tag expectations and added new tests for different call order scenarios
libs/typescript/core/tests/clients/client.test.ts Removed expectation of SPANS_LOCATION tag in TypeScript test

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Signed-off-by: Serena Ruan <serena.rxy@gmail.com>
Signed-off-by: Serena Ruan <serena.rxy@gmail.com>
@serena-ruan serena-ruan requested a review from B-Step62 December 4, 2025 04:55
Signed-off-by: Serena Ruan <serena.rxy@gmail.com>
@serena-ruan serena-ruan requested a review from B-Step62 December 4, 2025 10:32
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LGTM!

@B-Step62 B-Step62 added this pull request to the merge queue Dec 4, 2025
Merged via the queue into mlflow:master with commit d4c2305 Dec 4, 2025
49 of 51 checks passed
BenWilson2 pushed a commit to BenWilson2/mlflow that referenced this pull request Dec 4, 2025
Signed-off-by: Serena Ruan <serena.rxy@gmail.com>
BenWilson2 pushed a commit that referenced this pull request Dec 4, 2025
Signed-off-by: Serena Ruan <serena.rxy@gmail.com>
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