psycopg2.OperationalError: server closed the connection unexpectedly

[soar]

I'm using aiopg with SqlAlchemy support. All your examples looks like:

async with create_engine(...) as engine:
        async with engine.acquire() as conn:
            await conn.execute(...)

But I think this is wrong way: you shouldn't create_engine on every DB call. So engine object should be reusable instance in whole app. I've tried to use it like this:

# Somewhere on app init stage:
async def init_db_engine():
    db_engine = await aiopg.sa.create_engine(**engine_init_params)
    return db_engine

# Somewhere on app stop stage:
async def release_db_engine(db_engine):
    db_engine.close()
    return await db_engine.wait_closed()

# In some handlers:
async def get(*args, **kwargs):
    redirect_table = app.db.models.redirect.Redirect.__table__
    async with self.application.db.acquire() as conn:
        redirect_query = redirect_table.select().where(...)
        redirect_query_result = await conn.execute(redirect_query)
        redirect_info = await redirect_query_result.fetchone()

All looks like good, but... After some time of program inactivity any call to database fails with error:

	value = future.result()
	resp = yield from self._coro
	redirect_query_result = await conn.execute(redirect_query)
File "/usr/local/lib/python3.6/site-packages/aiopg/utils.py", line 72, in __await__
File "/usr/local/lib/python3.6/site-packages/aiopg/cursor.py", line 113, in execute
File "/usr/local/lib/python3.6/site-packages/aiopg/connection.py", line 237, in _poll
	yield from self._conn._poll(waiter, timeout)
	yield from cursor.execute(str(compiled), post_processed_params[0])
File "/usr/local/lib/python3.6/site-packages/aiopg/sa/connection.py", line 110, in _execute
	return fut.result()
File "/usr/local/lib/python3.6/asyncio/tasks.py", line 358, in wait_for
File "/usr/local/lib/python3.6/site-packages/aiopg/connection.py", line 134, in _ready
	yield from asyncio.wait_for(self._waiter, timeout, loop=self._loop)

psycopg2.OperationalError: server closed the connection unexpectedly before or while processing the request. This probably means the server terminated abnormally

Next call - works fine, so connection is reistablished.

What I've tried:

1. Add parameter pool_recycle=1 to engine_init_params - it is not recognized
2. Add minsize and maxsize parameters to engine_init_params - this didn't help

[soar]

I can't reproduce this issue on localhost (and/or) in debugger. But on real production environment in Docker, when DB and application running in different containers over network - it reproduces with 100% chance.

[asvetlov]

Perhaps a connection from pool goes to wrong state, we should drop it.

[jettify]

I believe issue resolved #373