Logfire causes sqlalchemy.exc.NoInspectionAvailable to raise when testing simple FastAPI+SQLModel app

[igorantonow314]

Description

Summary

I copied* this example from FastAPI's docs, added testing using TestClient and logfire with logfire.instrument_pydantic(), and encountered an error. The app without the line logfire.instrument_pydantic() works fine.
(*I removed irrelevant routes).

Details

Here is the index.py code:

from typing import Annotated

import logfire
from fastapi import Depends, FastAPI, HTTPException, Query
from fastapi.testclient import TestClient
from sqlmodel import Field, Session, SQLModel, create_engine, select



logfire.configure()
logfire.instrument_pydantic()


class HeroBase(SQLModel):
    name: str = Field(index=True)
    age: int | None = Field(default=None, index=True)


class Hero(HeroBase, table=True):
    id: int | None = Field(default=None, primary_key=True)
    secret_name: str


class HeroPublic(HeroBase):
    id: int


class HeroCreate(HeroBase):
    secret_name: str


class HeroUpdate(HeroBase):
    name: str | None = None
    age: int | None = None
    secret_name: str | None = None


sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"

connect_args = {"check_same_thread": False}
engine = create_engine(sqlite_url, connect_args=connect_args)


def create_db_and_tables():
    SQLModel.metadata.create_all(engine)


def get_session():
    with Session(engine) as session:
        yield session


SessionDep = Annotated[Session, Depends(get_session)]
app = FastAPI()


@app.on_event("startup")
def on_startup():
    create_db_and_tables()


@app.post("/heroes/", response_model=HeroPublic)
def create_hero(hero: HeroCreate, session: SessionDep):
    db_hero = Hero.model_validate(hero)
    session.add(db_hero)
    session.commit()
    session.refresh(db_hero)
    return db_hero




def test_create():
    with TestClient(app) as client:
        response = client.post('/heroes', json={"name": "some name", "age":123, "secret_name":"younewerguess"})
        assert response.status_code == 200

I ran pytest index.py and got the error:

sqlalchemy.exc.NoInspectionAvailable: No inspection system is available for object of type <class 'index.Hero'>

part of trace:

<...>
/home/igor/.local/lib/python3.10/site-packages/anyio/_backends/_asyncio.py:807: in run
    result = context.run(func, *args)
index.py:65: in create_hero
    db_hero = Hero.model_validate(hero)
/home/igor/.local/lib/python3.10/site-packages/sqlmodel/main.py:848: in model_validate
    return sqlmodel_validate(
/home/igor/.local/lib/python3.10/site-packages/sqlmodel/_compat.py:320: in sqlmodel_validate
    cls.__pydantic_validator__.validate_python(
/home/igor/.local/lib/python3.10/site-packages/logfire/integrations/pydantic.py:139: in wrapped_validator
    self._on_success(span, result)
/home/igor/.local/lib/python3.10/site-packages/logfire/integrations/pydantic.py:195: in _on_success
    self._set_span_attributes(
<...>
/home/igor/.local/lib/python3.10/site-packages/logfire/_internal/main.py:2090: in set_attribute
    self._json_schema_properties[key] = create_json_schema(value, set())
/home/igor/.local/lib/python3.10/site-packages/logfire/_internal/json_schema.py:149: in create_json_schema
    log_internal_error()
/home/igor/.local/lib/python3.10/site-packages/logfire/_internal/json_schema.py:127: in create_json_schema
    return _sqlalchemy_schema(obj, seen)
/home/igor/.local/lib/python3.10/site-packages/logfire/_internal/json_schema.py:344: in _sqlalchemy_schema
    state = sa_inspect(obj)

Full trace: pytest_output.txt

Possible reason

I may be wrong, this is just my opinion, but it may be useful.
Logfire is trying to log the instance of <class 'index.Hero'> (which is successfully created) and attempts to create json from it:
link to code line

def create_json_schema(obj: Any, seen: set[int]) -> JsonDict:
   <...>
  elif is_sqlalchemy(obj):
    return _sqlalchemy_schema(obj, seen)

is_sqlalchemy(obj) is True because <class 'index.Hero'> is instance of DeclarativeMeta.
But _sqlalchemy_schema(obj, seen) does something called

for cls in type_.__mro__:
  <...>

and mro is <class 'index.Hero'>, <class 'index.HeroBase'>, <class 'sqlmodel.main.SQLModel'>, <class 'pydantic.main.BaseModel'>, <class 'object'>. Maybe the SQLModel class is somehow "not connected" with sqlalchemy.inspect() and refuses to work properly, but I don't have enough knowledge about sqlalchemy, so I'm sorry for my (probably clueless) guesses.

Python, Logfire & OS Versions, related packages (not required)

logfire="2.11.0"
platform="Linux-6.8.0-49-generic-x86_64-with-glibc2.35"
python="3.10.12 (main, Nov  6 2024, 20:22:13) [GCC 11.4.0]"
[related_packages]
requests="2.32.3"
pydantic="2.10.3"
fastapi="0.115.6"
protobuf="5.29.2"
rich="13.9.4"
tomli="2.2.1"
executing="2.0.1"
opentelemetry-api="1.29.0"
opentelemetry-exporter-otlp-proto-common="1.29.0"
opentelemetry-exporter-otlp-proto-http="1.29.0"
opentelemetry-instrumentation="0.50b0"
opentelemetry-instrumentation-asgi="0.50b0"
opentelemetry-instrumentation-fastapi="0.50b0"
opentelemetry-instrumentation-sqlalchemy="0.50b0"
opentelemetry-proto="1.29.0"
opentelemetry-sdk="1.29.0"
opentelemetry-semantic-conventions="0.50b0"
opentelemetry-util-http="0.50b0"

[Kludex]

I've found this issue on SQLModel itself: fastapi/sqlmodel#71.

That said... This issue only happens with instrument_pydantic.

[Kludex]

We can modify the is_sqlalchemy function to check if we can use sqlalchemy.inspect, but it seems our Pydantic plugin is doing something here.

[alexmojaki]

Fix released in 2.11.1