PostgreSQL: server closed the connection unexpectedly

[kovaxur]

Hi,
I started to use ponyorm for my project, I found the following problem:

Steps to reproduce:

1. I start my application, everything is fine, I can work with the database properly
   (2. I can do stress tests all night, everything goes well)
2. If I don't do anything for like 10-15 minutes and then I try to execute something, I get the following exception message:

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

Trace:
File \"<string>\", line 2, in __iter__\n","  File \"/usr/lib/python3.6/site-packages/pony/utils/utils.py\", line 58, in cut_traceback\n    return func(*args, **kwargs)\n","  
File \"/usr/lib/python3.6/site-packages/pony/orm/core.py\", line 5506, in __iter__\n    return iter(query._fetch())\n","  
File \"/usr/lib/python3.6/site-packages/pony/orm/core.py\", line 5343, in _fetch\n    cursor = database._exec_sql(sql, arguments)\n","  
File \"/usr/lib/python3.6/site-packages/pony/orm/core.py\", line 820, in _exec_sql\n    connection = cache.reconnect(e)\n","  
File \"/usr/lib/python3.6/site-packages/pony/orm/core.py\", line 1625, in reconnect\n    if not provider.should_reconnect(exc): reraise(*sys.exc_info())\n","  
File \"/usr/lib/python3.6/site-packages/pony/utils/utils.py\", line 87, in reraise\n    try: raise exc.with_traceback(tb)\n"," 
File \"/usr/lib/python3.6/site-packages/pony/orm/core.py\", line 818, in _exec_sql\n    try: new_id = provider.execute(cursor, sql, arguments, returning_id)\n","  File \"<string>\", line 2, in execute\n","  
File \"/usr/lib/python3.6/site-packages/pony/orm/dbapiprovider.py\", line 61, in wrap_dbapi_exceptions\n    raise OperationalError(e)\n"

Versions:

pony.__version__
'0.7.3'
psycopg2.__version__
'2.7.5 (dt dec pq3 ext lo64)'
python 3.6

Maybe this is rather an architectural problem in my code, however I used the same model as in the examples.

Thanks

[kovaxur]

I did some debugging, so if I don't do anything, the connection probably times out after a while, in core.py line 819, an exception is catched (cursor's closed attribute is True)

        try: new_id = provider.execute(cursor, sql, arguments, returning_id)
        except Exception as e:
            connection = cache.reconnect(e)
            cursor = connection.cursor()
            if local.debug: log_sql(sql, arguments)
            t = time()
            new_id = provider.execute(cursor, sql, arguments, returning_id)

The exception is caught, and now it tries to reconnect:
The exception is re-raised during the reconnect:

 def reconnect(cache, exc):
        provider = cache.database.provider
        if exc is not None:
            exc = getattr(exc, 'original_exc', exc)
            if not provider.should_reconnect(exc): reraise(*sys.exc_info())

[kovaxur]

The should_reconnect functions:

exc.pgcode = None
exc.pgerror = 'server closed the connection unexpectedly
	This probably means the server terminated abnormally
	before or while processing the request.'
exc.cursor = (not none)

[kozlovsky]

Thanks for reporting, now Pony will again reconnect to PostgreSQL database automatically after the server closes the connection.

By the way, it looks strange that your server drops connection after 10-15 minutes, maybe there is some misconfiguration in your database connection settings.

[Gefuxing]

How to solve this problem in the configuration file how to configure