SQLAlchemy 查询有时工作正常，有时返回 sqlalchemy.exc.InternalError

Question

我有一个看起来像数据库的问题。

我正在使用 FastAPI 和 SQLAlchemy。

我有一个 API 端点，它返回数据库中的所有对象。

主程序

from session import session
from models import *

@app.get("/source/")
async def get_news(request: Request):
    sources = Source.get_sources()
    if sources is None:
        raise HTTPException(status_code=404, detail="No sources") 
    
    return JSONResponse([s.to_dict() for s in sources])

import os
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

from sqlalchemy import create_engine
from sqlalchemy.orm import Session



devprod = os.environ.get('DEVPROD')
if devprod:
    logging.debug('Running ' + devprod)
if devprod == 'DEV':
    engine_string = 'url'
elif devprod == 'PROD':
    engine_string = 'sqlite+pysqlite:///:memory:'
else:
    engine_string = 'ur'
engine = create_engine(engine_string, echo=True, future=True)
session = Session(engine)

源代码.py

def get_sources():
    return session.query(Source).all()

然后我将其部署到 heroku 并运行 Heroku 提供的 PostgreSQL。

现在我调用端点一次：

2022-03-18T12:45:08.807470+00:00 heroku[router]: at=info method=GET path="/source/" host=____ request_id=c383505b-3dd5-45c7-86ae-d6b5a0173d70 fwd="91.103.31.14" dyno=web.1 connect=0ms service=3ms status=200 bytes=1338 protocol=https

一切都很好，得到了 200 和正确的回应。

2 分钟后尝试相同的请求：

2022-03-18T12:46:03.613719+00:00 heroku[router]: at=info method=GET path="/source/" host=_____ request_id=eb9baba7-12c1-4087-9828-41e64960853c fwd="91.103.31.14" dyno=web.1 connect=0ms service=3ms status=500 bytes=193 protocol=https

日志指出以下错误：

2022-03-18T12:46:03.615467+00:00 app[web.1]:     return session.query(Source).all()
2022-03-18T12:46:03.615468+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/query.py", line 2759, in all
2022-03-18T12:46:03.615468+00:00 app[web.1]:     return self._iter().all()
2022-03-18T12:46:03.615468+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/query.py", line 2894, in _iter
2022-03-18T12:46:03.615468+00:00 app[web.1]:     result = self.session.execute(
2022-03-18T12:46:03.615468+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 1692, in execute
2022-03-18T12:46:03.615468+00:00 app[web.1]:     result = conn._execute_20(statement, params or {}, execution_options)
2022-03-18T12:46:03.615469+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1614, in _execute_20
2022-03-18T12:46:03.615469+00:00 app[web.1]:     return meth(self, args_10style, kwargs_10style, execution_options)
2022-03-18T12:46:03.615469+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/sql/elements.py", line 325, in _execute_on_connection
2022-03-18T12:46:03.615469+00:00 app[web.1]:     return connection._execute_clauseelement(
2022-03-18T12:46:03.615469+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1481, in _execute_clauseelement
2022-03-18T12:46:03.615470+00:00 app[web.1]:     ret = self._execute_context(
2022-03-18T12:46:03.615470+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1845, in _execute_context
2022-03-18T12:46:03.615472+00:00 app[web.1]:     self._handle_dbapi_exception(
2022-03-18T12:46:03.615472+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 2026, in _handle_dbapi_exception
2022-03-18T12:46:03.615472+00:00 app[web.1]:     util.raise_(
2022-03-18T12:46:03.615473+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/util/compat.py", line 207, in raise_
2022-03-18T12:46:03.615473+00:00 app[web.1]:     raise exception
2022-03-18T12:46:03.615473+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1802, in _execute_context
2022-03-18T12:46:03.615473+00:00 app[web.1]:     self.dialect.do_execute(
2022-03-18T12:46:03.615473+00:00 app[web.1]:   File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/default.py", line 732, in do_execute
2022-03-18T12:46:03.615474+00:00 app[web.1]:     cursor.execute(statement, parameters)
2022-03-18T12:46:03.615474+00:00 app[web.1]: sqlalchemy.exc.InternalError: (psycopg2.errors.InFailedSqlTransaction) current transaction is aborted, commands ignored until end of transaction block

这怎么可能？

Answer 1

我通过在 postgresql 中运行命令解决了这个问题：

SELECT pid , query, * from pg_stat_activity
  WHERE state != 'idle' ORDER BY xact_start;

然后对于每个事务 ID，我执行了这个命令：

select pg_terminate_backend(2427731);

然后我也运行命令：

from session import session

session.rollback()

问题消失了。 猜猜我有一个卡住的交易导致了一个问题。