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Date: Wed, 21 Mar 2012 13:34:29 -0700
Subject: Re: Best way to disconnect from ldap?
From: Chris Rebert <clp2@rebertia.com>
To: John Gordon <gordon@panix.com>
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On Wed, Mar 21, 2012 at 12:30 PM, John Gordon <gordon@panix.com> wrote:
> I'm writing an application that interacts with ldap, and I'm looking
> for advice on how to handle the connection. =C2=A0Specifically, how to
> close the ldap connection when the application is done.
>
> I wrote a class to wrap an LDAP connection, similar to this:
>
> =C2=A0 =C2=A0import ldap
> =C2=A0 =C2=A0import ConfigParser
>
> =C2=A0 =C2=A0class MyLDAPWrapper(object):
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0def __init__(self):
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0config =3D ConfigParser.SafeConf=
igParser()
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0config.read('sample.conf')
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0uri =3D config.get('LDAP', 'uri'=
)
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0user =3D config.get('LDAP', 'use=
r')
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0password =3D config.get('LDAP', =
'password')
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0self.ldapClient =3D ldap.initial=
ize(uri)
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0self.ldapClient.simple_bind_s(us=
er, password)
>
> My question is this: what is the best way to ensure the ldap connection
> gets closed when it should? =C2=A0I could write an explicit close() metho=
d,
> but that seems a bit messy; there would end up being lots of calls to
> close() scattered around in my code (primarily inside exception handlers.=
)
>
> Or I could write a __del__ method:
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0def __del__(self):
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0self.ldapClient.unbind_s()
>
> This seems like a much cleaner solution, as I don't ever have to worry
> about closing the connection; it gets done automatically.

Yes, but not necessarily in a timely manner. Since its uses reference
counting, CPython /just so happens/ to finalize
non-cyclically-referenced objects promptly when they go out of scope,
but Python-the-language makes no such guarantee, and indeed some of
the other Python implementations explicitly disclaim that there may be
a significant delay before finalization is performed.

> I haven't ever used __del__ before. =C2=A0Are there any 'gotchas' I need =
to
> worry about?

In addition to the aforementioned problem regarding portability to
other Python implementations, see also the Warning box under:
http://docs.python.org/reference/datamodel.html#object.__del__

I concur with J.'s context manager suggestion.

Cheers,
Chris