I have a system composed by client where runs sqlalchemy and a remote
server where runs MySQL server database.
With sqlalchemy I use to setup session:
# db_host is the ip address of remote server
db_url = 'mysql+mysqldb://db_user:db_pswd@db_host/db_name'
db_engine = create_engine(db_url)
db_session_factory = sessionmaker(bind=db_engine)
db_session = scoped_session(db_session_factory)
and later, whenever I have data to dump I do something like:
# dumping phase
db_session.add(data)
db_session.commit()
I would need to handle, from the client side, an unexpected disconnection
of the server from the network (e.g. it switches off, the internet goes
down or merely I unplug the ethernet cable...).
I would like to get an exception or something to handle this during the
dumping phase, for instance setting a connection timeout on client side.
In case of exception I could dump the data on a local database for instance.
If server goes down during dumping phase, it will wait about 15 minutes and
then sqlalchemy raises an exception like:
sqlalchemy.exc.OperationalError: (OperationalError) (2013, 'Lost
connection to MySQL server during query')
sqlalchemy.exc.OperationalError: (OperationalError) (2003, "Can't
connect to MySQL server on...)
According to:
http://stackoverflow.com/questions/1209640/how-do-you-control-mysql-timeouts-from-sqlalchemy
That time of 15 minutes is related to the TCP level configuration of the
client, and I could reduce it for instance with:
~# sysctl net.ipv4.tcp_retries2=1
In this way I could get the exception in 1 second, but this configuration
change for all the TCP connections of the operating system, that is
undesirable.
Is there a way to control the connection timeout on client side only for
the sqlalchemy session?
And get an exception if the server cannot be reached during the dumping
phase, after a limited time duration (e.g. after 1 second, I don't want to
wait 15 minutes)?
Thanks
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http://www.sqlalchemy.org/
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