python - Why does SQLAlchemy/mysql keep timing out on me? -

i have 2 functions need executed , first takes 4 hours execute. both use sqlalchemy:

def first():     session = dbsession     rows = session.query(mytable).order_by(mytable.col1.desc())[:150]      i,row in enumerate(rows):         time.sleep(100)     print i, row.accession  def second():     print "going onto second function"     session = dbsession     new_row = session.query(anothertable).order_by(anothertable.col1.desc()).first()      print 'new row: ', new_row.accession   first() second() 

and here how define dbsession:

from sqlalchemy.ext.declarative import declarative_base sqlalchemy.orm import scoped_session, sessionmaker sqlalchemy import create_engine  engine = create_engine('mysql://blah:blah@blah/blahblah',echo=false,pool_recycle=3600*12) dbsession = scoped_session(sessionmaker(autocommit=false, autoflush=false, bind=engine)) base = declarative_base()     base.metadata.bind = engine    

first() finishes fine (takes 4 hrs) , see "going onto second function" printed gives me error:

sqlalchemy.exc.operationalerror: (operationalerror) (2006, 'mysql server has gone away') 

from reading docs thought assigning session=dbsession 2 different session instances , second() wouldn't timeout. i've tried playing pool_recycle , doesn't seem have effect here. in real world, can't split first() , second() 2 scripts: second() has execute after first()

assigning session=dbsession 2 different session instances

that isn't true. session = dbsession local variable assignment, , cannot override local variable assignment in python (you can override instance member assignment, that's unrelated).

another thing note scoped_session produces, default, thread-local scoped session (i.e. codes in same thread have same session). since call first() , second() in same thread, 1 , same session.

one thing can use regular (unscoped) session, manage session scope manually , create new session in both function. alternatively, can check doc how define custom session scope.