problem with postgres+asyncpg default connector

[Milanomac]

I am trying to connect TruSession to a postgres+asyncpg database. I used this link as reference. Right after I see that it TruSession was initialized with my db url, I am getting a traceback (below). Is it possible to have a asyncpg postgres as default connector instead of the default sqlite. Note: I want to have OTEL enabled.

Traceback (most recent call last):
File "/usr/local/lib/python3.12/runpy.py", line 198, in _run_module_as_main
return _run_code(code, main_globals, None,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.12/runpy.py", line 88, in _run_code
exec(code, run_globals)
File "/home/jovyan/.local/share/code-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/main.py", line 71, in
cli.main()
File "/home/jovyan/.local/share/code-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/../debugpy/server/cli.py", line 501, in main
run()
File "/home/jovyan/.local/share/code-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/../debugpy/server/cli.py", line 351, in run_file
runpy.run_path(target, run_name="main")
File "/home/jovyan/.local/share/code-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 310, in run_path
return _run_module_code(code, init_globals, run_name, pkg_name=pkg_name, script_name=fname)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/.local/share/code-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 127, in _run_module_code
_run_code(code, mod_globals, init_globals, mod_name, mod_spec, pkg_name, script_name)
File "/home/jovyan/.local/share/code-server/extensions/ms-python.debugpy-2025.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 118, in _run_code
exec(code, run_globals)
File "/home/jovyan/dapfs-core/generative-ai/agent/chatbot/backend.py", line 157, in
main()
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/click/core.py", line 1485, in call
return self.main(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/click/core.py", line 1406, in main
rv = self.invoke(ctx)
^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/click/core.py", line 1269, in invoke
return ctx.invoke(self.callback, **ctx.params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/click/core.py", line 824, in invoke
return callback(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/dapfs-core/generative-ai/agent/chatbot/backend.py", line 75, in main
connector = DefaultDBConnector(database_url=postgres_uri)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/trulens/core/database/connector/default.py", line 82, in init
self._db.check_db_revision()
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/trulens/core/database/sqlalchemy.py", line 278, in check_db_revision
db_utils.check_db_revision(self.engine, self.table_prefix)
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/trulens/core/database/utils.py", line 94, in check_db_revision
ins = sqlalchemy.inspect(engine)
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/inspection.py", line 140, in inspect
ret = reg(subject)
^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/engine/reflection.py", line 313, in _engine_insp
return Inspector._construct(Inspector._init_engine, bind)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/engine/reflection.py", line 246, in _construct
init(self, bind)
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/engine/reflection.py", line 257, in _init_engine
engine.connect().close()
^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/engine/base.py", line 3285, in connect
return self._connection_cls(self)
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/engine/base.py", line 143, in init
self._dbapi_connection = engine.raw_connection()
^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/engine/base.py", line 3309, in raw_connection
return self.pool.connect()
^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/pool/base.py", line 447, in connect
return _ConnectionFairy._checkout(self)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/pool/base.py", line 1264, in _checkout
fairy = _ConnectionRecord.checkout(pool)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/pool/base.py", line 711, in checkout
rec = pool._do_get()
^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/pool/impl.py", line 177, in _do_get
with util.safe_reraise():
^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/util/langhelpers.py", line 224, in exit
raise exc_value.with_traceback(exc_tb)
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/pool/impl.py", line 175, in _do_get
return self._create_connection()
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/pool/base.py", line 388, in _create_connection
return _ConnectionRecord(self)
^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/pool/base.py", line 673, in init
self.__connect()
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/pool/base.py", line 899, in __connect
with util.safe_reraise():
^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/util/langhelpers.py", line 224, in exit
raise exc_value.with_traceback(exc_tb)
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/pool/base.py", line 895, in __connect
self.dbapi_connection = connection = pool._invoke_creator(self)
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/engine/create.py", line 661, in connect
return dialect.connect(*cargs, **cparams)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/engine/default.py", line 630, in connect
return self.loaded_dbapi.connect(*cargs, **cparams) # type: ignore[no-any-return] # NOQA: E501
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/dialects/postgresql/asyncpg.py", line 955, in connect
await_only(creator_fn(*arg, **kw)),
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jovyan/venv-agent/lib/python3.12/site-packages/sqlalchemy/util/_concurrency_py3k.py", line 123, in await_only
raise exc.MissingGreenlet(
sqlalchemy.exc.MissingGreenlet: greenlet_spawn has not been called; can't call await_only() here. Was IO attempted in an unexpected place? (Background on this error at: https://sqlalche.me/e/20/xd2s)

[dosubot[bot]]

TruSession and DefaultDBConnector currently only support synchronous SQLAlchemy engines and database URLs, like postgresql+psycopg://user:pass@host/db. They do not support asyncpg or async SQLAlchemy engines out of the box. If you try to use asyncpg (e.g., with a URL like postgresql+asyncpg://...), you'll get a MissingGreenlet error because the connector runs in a synchronous context and expects sync database operations, while asyncpg requires an async event loop and await calls source.

To connect to PostgreSQL, use the synchronous psycopg driver as shown in the docs and examples source. If you need async database support, you would need to refactor the connector and session logic to work with async SQLAlchemy engines and asyncpg, which is not currently supported.

OTEL tracing is enabled by default and works with the supported synchronous connectors. There is no special configuration for async database connections, since async is not supported source.

For now, use the synchronous psycopg driver for PostgreSQL with TruSession. If you need async database operations, consider isolating those from TruSession logging, or use a separate logging mechanism.

To reply, just mention @dosu.

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[sfc-gh-jreini]

@Milanomac - looks like we don't support postgres yet but we can add support by just adding this json extract patch as dosu suggests. Would you be willing to help us test the change?

[Milanomac]

sfc-gh-jreini this patch works for recording and feedback computation but it won't work for dashboard. I tried it but TruLens dashboard emits sa.func.json_extract in several places. The dashboard:

• Builds queries
• Caches them with Streamlit
• Uses sa.func.json_extract directly
  So patching _json_extract_otel is not sufficient. I don't understand why are you making postgres connector available when queries are hardcoded for different flavour.

[sfc-gh-jreini]

Thanks for the quick response. We'll investigate how we can support this further next week.

[sfc-gh-jreini]

Hi @Milanomac - We've added PostgreSQL support using the synchronous psycopg2 driver. Expecting this to make TruLens 2.6 release this week.

The asyncpg driver you were using requires SQLAlchemy's async extension, which TruLens doesn't support yet. However, for most use cases, the sync driver works great - TruLens already handles recording and feedback evaluation in background threads, so you shouldn't see any blocking on your main application.

If your application specifically requires the async database support, let me know.

[sfc-gh-jreini]

Hey @Milanomac - following up to let you know we released TruLens 2.6 with postgres support. Please let us know if you require further support (such as needing the asyncpg driver).