Error message when program is closed：sqlalchemy.pool.impl.NullPool

[WTSRUVF]

Bug summary

When I execute the program in the documentation, this error is sometimes reported after the program is executed.

code

from prefect import flow, task

@task
def say_hello(name):
    return f"Hello {name}!"

@task
def print_result(result):
    print(type(result))
    print(result)

@flow(name="hello-flow")
def hello_world():
    future = say_hello.submit("Marvin")
    print_result.submit(future).wait()

hello_world()

error

20:29:07.002 | ERROR   | sqlalchemy.pool.impl.NullPool - Exception closing connection <AdaptedConnection <Connection(Thread-16, started daemon 139909163644608)>>
Traceback (most recent call last):
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/sqlalchemy/pool/base.py", line 376, in _close_connection
    self._dialect.do_close(connection)
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/sqlalchemy/engine/default.py", line 708, in do_close
    dbapi_connection.close()
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/sqlalchemy/dialects/sqlite/aiosqlite.py", line 275, in close
    self.await_(self._connection.close())
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/sqlalchemy/util/_concurrency_py3k.py", line 132, in await_only
    return current.parent.switch(awaitable)  # type: ignore[no-any-return,attr-defined] # noqa: E501
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/sqlalchemy/util/_concurrency_py3k.py", line 196, in greenlet_spawn
    value = await result
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/aiosqlite/core.py", line 178, in close
    await self._execute(self._conn.close)
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/aiosqlite/core.py", line 132, in _execute
    return await future
asyncio.exceptions.CancelledError

If DaskTaskRunner is used, the following error is reported.

14:25:36.839 | ERROR   | sqlalchemy.pool.impl.NullPool - Exception during reset or similar
Traceback (most recent call last):
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/sqlalchemy/pool/base.py", line 986, in _finalize_fairy
    fairy._reset(
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/sqlalchemy/pool/base.py", line 1432, in _reset
    pool._dialect.do_rollback(self)
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/sqlalchemy/engine/default.py", line 699, in do_rollback
    dbapi_connection.rollback()
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/sqlalchemy/dialects/sqlite/aiosqlite.py", line 263, in rollback
    self.await_(self._connection.rollback())
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/sqlalchemy/util/_concurrency_py3k.py", line 132, in await_only
    return current.parent.switch(awaitable)  # type: ignore[no-any-return,attr-defined] # noqa: E501
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/sqlalchemy/util/_concurrency_py3k.py", line 196, in greenlet_spawn
    value = await result
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/aiosqlite/core.py", line 169, in rollback
    await self._execute(self._conn.rollback)
  File "/root/.pyenv/versions/3.9.16/lib/python3.9/site-packages/aiosqlite/core.py", line 132, in _execute
    return await future
asyncio.exceptions.CancelledError

Version info

Version:             3.1.10
API version:         0.8.4
Python version:      3.9.16
Git commit:          b11b56fc
Built:               Tue, Dec 24, 2024 10:58 PM
OS/Arch:             linux/x86_64
Profile:             ephemeral
Server type:         ephemeral
Pydantic version:    2.10.4
Server:
  Database:          sqlite
  SQLite version:    3.45.1

Additional context

Package                   Version
------------------------- -----------
aiosqlite                 0.20.0
alembic                   1.14.0
amqp                      5.3.1
annotated-types           0.7.0
anyio                     4.7.0
apprise                   1.9.1
APScheduler               3.11.0
asgi-lifespan             2.1.0
async-timeout             5.0.1
asyncpg                   0.30.0
attrs                     24.3.0
bce-python-sdk            0.9.25
beautifulsoup4            4.12.3
billiard                  4.2.1
blinker                   1.9.0
bs4                       0.0.2
cachetools                5.5.0
celery                    5.4.0
certifi                   2024.12.14
cffi                      1.17.1
charset-normalizer        3.4.1
click                     8.1.8
click-didyoumean          0.3.1
click-plugins             1.1.1
click-repl                0.3.0
cloudpickle               3.1.0
colorama                  0.4.6
coolname                  2.2.0
croniter                  3.0.4
cryptography              44.0.0
dask                      2024.8.0
dateparser                1.2.0
Deprecated                1.2.15
distributed               2024.8.0
docker                    7.1.0
exceptiongroup            1.2.2
fastapi                   0.115.6
Flask                     3.1.0
Flask-SQLAlchemy          3.1.1
fsspec                    2024.12.0
future                    1.0.0
graphviz                  0.20.3
greenlet                  3.1.1
griffe                    1.5.1
h11                       0.14.0
h2                        4.1.0
hpack                     4.0.0
httpcore                  1.0.7
httpx                     0.28.1
humanize                  4.11.0
hyperframe                6.0.1
idna                      3.10
importlib_metadata        8.5.0
itsdangerous              2.2.0
jieba                     0.42.1
Jinja2                    3.1.5
jinja2-humanize-extension 0.4.0
joblib                    1.4.2
jsonpatch                 1.33
jsonpointer               3.0.0
jsonschema                4.23.0
jsonschema-specifications 2024.10.1
kombu                     5.4.2
Levenshtein               0.26.1
locket                    1.0.0
lxml                      5.2.2
Mako                      1.3.8
Markdown                  3.7
markdown-it-py            3.0.0
MarkupSafe                3.0.2
mdurl                     0.1.2
msgpack                   1.1.0
nltk                      3.9.1
numpy                     2.0.2
oauthlib                  3.2.2
opentelemetry-api         1.29.0
orjson                    3.10.12
packaging                 24.2
pandas                    2.2.3
partd                     1.4.2
pathspec                  0.12.1
pendulum                  3.0.0
pip                       22.0.4
prefect                   3.1.10
prefect-dask              0.3.2
prometheus_client         0.21.1
prompt_toolkit            3.0.48
psutil                    6.1.1
py4j                      0.10.9.7
pycparser                 2.22
pycrypto                  2.6.1
pycryptodome              3.21.0
pydantic                  2.10.4
pydantic_core             2.27.2
pydantic-extra-types      2.10.1
pydantic-settings         2.7.0
Pygments                  2.18.0
PyMySQL                   1.1.1
pyspark                   3.5.4
python-dateutil           2.9.0.post0
python-dotenv             1.0.1
python-Levenshtein        0.26.1
python-slugify            8.0.4
python-socks              2.5.3
pytz                      2024.2
PyYAML                    6.0.2
RapidFuzz                 3.11.0
readchar                  4.2.1
redis                     5.2.1
referencing               0.35.1
regex                     2024.11.6
requests                  2.32.3
requests-oauthlib         2.0.0
rfc3339-validator         0.1.4
rich                      13.9.4
rpds-py                   0.22.3
ruamel.yaml               0.18.6
ruamel.yaml.clib          0.2.12
setuptools                58.1.0
shellingham               1.5.4
six                       1.17.0
sniffio                   1.3.1
sortedcontainers          2.4.0
soupsieve                 2.6
SQLAlchemy                2.0.36
starlette                 0.41.3
tblib                     3.0.0
text-unidecode            1.3
time-machine              2.16.0
timeout-decorator         0.5.0
toml                      0.10.2
toolz                     1.0.0
tornado                   6.4.2
tqdm                      4.67.1
typer                     0.12.5
typing_extensions         4.12.2
tzdata                    2024.2
tzlocal                   5.2
ujson                     5.10.0
urllib3                   2.3.0
uvicorn                   0.34.0
vine                      5.1.0
wcwidth                   0.2.13
websockets                13.1
Werkzeug                  3.1.3
wrapt                     1.17.0
zhon                      2.1.1
zict                      3.0.0
zipp                      3.21.0

[desertaxle]

Thanks for the issue @WTSRUVF! It looks like you're running against an ephemeral server, and something is getting canceled as the ephemeral server is shutting down. It's likely related to .submit not being used since those runs will be executed in a separate thread or on a Dask cluster.

I'm not able to reproduce this issue on my machine. Can you share the full log output of a flow run where you see this error? Also, do you see anything strange in the UI for flow runs where you see this error?