Re: [cx-oracle-users] How to deal with lost connection to Oracle ?

[<prz...@po...>]

On Wed, Jul 21, 2010 at 08:05:13AM -0600, Anthony Tuininga wrote:
> On Wed, Jul 21, 2010 at 7:14 AM,  <prz...@po...> wrote:
> > Hello,
> >
> > (I am python and cx_oracle beginner so please excuse me ...)
> >
> > I am going to write small python application which will fetch some small
> > data from many Oracles _once_ a minute for 24h/365.
> > These Oracles are backuped offline (shutdown, snapshot, startup).
> 
> Hmm, any reason these aren't backed up online? That would make the
> databases available 24/7. That doesn't eliminate the problem since
> they could go down for other reasons but it eliminates most of the
> problems.

I know. But this is beyond my ability - our DBAs didn't make decision to change it.

> > Each Oracle has its own backup time. What I need is to
> > properly handle lost connections , e.g.:
> > minute 1: fetch data
> > minute 2: fetch data
> > minute 3: fetch data
> > minute 4: lost connection [1] (how to detect it ?) - backup started
> > minute 5: try to connect - failed [2] (how to detect it ?) - ongoing backup process
> > minute 6: try to connect - failed ...
> > minute 7: try to connect - failed ...
> > minute 8: try to connect - failed ...
> > minute 9: try to connect - successful ...
> > minute10: fetch data
> >
> > How can I detect [1] and [2] ?
> 
> It depends what version of Oracle you are using. For 10.2 and up you
> can use connection.ping() which will attempt to contact the server and
> raise an error if the connection has dropped.
> 
> try:
>     connection.ping()
> except cx_Oracle.DatabaseError:
>     print "*** Connection dropped ***"
> 
> The same goes for attempting to connect
> 
> try:
>     connection = cx_Oracle.Connection(connectString)
> except cx_Oracle.DatabaseError:
>     print "*** Connection failed to establish ***"
> 
> Note that those catch any database exception, not just "the database
> is not available". If you need to be more careful about which
> exceptions to catch then you need something like this:
> 
> try:
>     connnection = cx_Oracle.Connection(connectString)
> except cx_Oracle.DatabaseError, e:
>     error, = e.args
>     if error.code == 1017:
>         print "*** Invalid username/password ***"
>     else:
>         print "*** Some other error:", error.message, "***"

I need just availability of the database. Which exception would be
the most useful ?


Regards
Przemyslaw Bak (przemol)





























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