python - tornado + momoko doesn't handle connection -

i use tornado (4.2.1) + momoko (2.2.0) + psycopg2 (2.6.1) small web application , works ok until postgresql server close connection. after every db.execute() command receive error message:

traceback (most recent call last):       file "c:\python27\lib\site-packages\tornado-4.2.1-py2.7-win32.egg\tornado\web.py", line 1415, in _execute         result = yield result       file "c:\python27\lib\site-packages\tornado-4.2.1-py2.7-win32.egg\tornado\gen.py", line 870, in run         value = future.result()       file "c:\python27\lib\site-packages\tornado-4.2.1-py2.7-win32.egg\tornado\concurrent.py", line 215, in result         raise_exc_info(self._exc_info)       file "c:\python27\lib\site-packages\tornado-4.2.1-py2.7-win32.egg\tornado\gen.py", line 876, in run         yielded = self.gen.throw(*exc_info)       file "server.py", line 63, in         cursor = yield self.db.execute(query)       file "c:\python27\lib\site-packages\tornado-4.2.1-py2.7-win32.egg\tornado\gen.py", line 870, in run         value = future.result()       file "c:\python27\lib\site-packages\tornado-4.2.1-py2.7-win32.egg\tornado\concurrent.py", line 215, in result         raise_exc_info(self._exc_info)       file "d:\work\program-stat\momoko\connection.py", line 453, in when_available         future_or_result = method(conn, *args, **kwargs)       file "d:\work\program-stat\momoko\connection.py", line 743, in execute         cursor.execute(operation, parameters)       file "c:\python27\lib\site-packages\psycopg2\extras.py", line 288, in execute         return super(namedtuplecursor, self).execute(query, vars)     operationalerror: server closed connection unexpectedly         means server terminated abnormally         before or while processing request. 

here code:

import os import tornado.httpserver import tornado.ioloop import tornado.options import tornado.web import momoko  tornadotools.route import route psycopg2.extras import namedtuplecursor  import environments env   tornado.options.define("port", default=9999, help="run on given port", type=int) tornado.options.define("pgsql_host", default=env.db_host, help="database host") tornado.options.define("pgsql_database", default=env.db_database, help="database name") tornado.options.define("pgsql_user", default=env.db_login, help="database user") tornado.options.define("pgsql_password", default=env.db_password, help="database password")   class application(tornado.web.application):     def __init__(self):         handlers = route.routes()         settings = dict(             template_path=os.path.join(os.path.dirname(__file__), "templates"),             static_path=os.path.join(os.path.dirname(__file__), "static"),             debug=true,         )         tornado.web.application.__init__(self, handlers, **settings)          # have 1 global connection db across handlers         self.db = momoko.pool(             dsn='dbname=%s user=%s password=%s '                 'host=%s port=5432' % (                     tornado.options.options.pgsql_database,                     tornado.options.options.pgsql_user,                     tornado.options.options.pgsql_password,                     tornado.options.options.pgsql_host),             cursor_factory=namedtuplecursor,         )         self.db.connect()   class basehandler(tornado.web.requesthandler):     @property     def db(self):         return self.application.db  @route(r"/") class homehandler(basehandler):     def get(self):         self.write("<ul>")         self.write("<li><a href='/test'>test page</a>")         self.write("</ul>")         self.finish()  @route(r"/test") class mogrifyhandler(basehandler):      @tornado.web.asynchronous     @tornado.gen.coroutine     def get(self):         cursor = yield self.db.execute("select %s t;", (1,))         self.render("test.html", result=cursor.fetchall())   def main():     tornado.options.parse_command_line()     http_server = tornado.httpserver.httpserver(application())     http_server.listen(tornado.options.options.port)     tornado.ioloop.ioloop.instance().start()   if __name__ == "__main__":     main() 

how handle exception , reconnect db automatically without restarting app?

you can add parameter:

raise_connect_errors=false, 

when create connection pool:

self.db = momoko.pool(     dsn='dbname=%s user=%s password=%s '         'host=%s port=5432' % (             tornado.options.options.pgsql_database,             tornado.options.options.pgsql_user,             tornado.options.options.pgsql_password,             tornado.options.options.pgsql_host),     cursor_factory=namedtuplecursor,     raise_connect_errors=false, ) 

but not helpful.