[ftputil] How to correctlry close a ftp connection

[Yvan Strahm]

On Sun, Dec 14, 2008 at 10:48 AM, Stefan Schwarzer <
sschwarzer at sschwarzer.net> wrote:

> Hello,
>
> On 2008-12-12 14:47, Stefan Schwarzer wrote:
> > Regarding the symmetry of the FTPHost construction and calling
> > the close method, at first sight this looks well. However, if the
> > constructor fails, the close method won't be called, so that may
> > be the reason why you exhaust the possible number of connections.
>
> It seems I was a bit hasty here. If the _constructor_ fails, the
> connection wouldn't have been established in the first place, so
> it's not necessary to close it. "Closing" a connection which
> actually isn't there may rather cause an exception _in the
> "close" call_.
>
> More important, thus, usually are exceptions which happen after
> the construction.
>
> > I think you should use a try ... finally construct:
> >
> > try:
> >     print "CONNECTING TO "+ ftp + ftp_dir+file+"\n"
> >     host=ftputil.FTPHost(ftp,user,password)
> >     try:
>
> That's why the "try" comes _after_ calling the constructor. If
> the connection wasn't opened, it doesn't need to be closed.
>
> It's similar in the Python idiom
>
> fobj = open(...)
> try:
>    ...
> finally:
>    fobj.close()
>
> >         host.chdir(ftp_dir+file)
> >         names=host.listdir(host.curdir)
> >         for name in names:
> >             if host.path.isfile(name):
> >                 p="pep"
> >                 m_pep=re.search(p,name)
> >                 if m_pep:
> >                     returned=name
> >                     host.download_if_newer(name,target,'b')
>
> Besides: Behind the scenes download_if_newer opens a new
> connection to the FTP server in order to make a file object. So
> not only explicit constructor calls generate connections. (There
> shouldn't be connection leaks because of that because unused file
> objects are reused, and they are closed when the FTPHost object
> is closed.)
>
> >     finally:
> >         host.close()
> > except:
> >     ...
>
> The curious thing is that your problem comes from the code which
> is executed _before_ you call the constructor that fails with an
> exception. :-)
>
> Best regards,
> Stefan
>

Hello Stefan,

Thanks! the nested try:try:finally:except is doing the trick. I didn't count
how many time in my original script the first try was " tried " without
success  but I suspect that this was the cause of all these not closed
connection, as you pointed out in your first reply.

Thanks a lot for your help
Best regards
yvan
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://codespeak.net/pipermail/ftputil/attachments/20081215/84a9ef81/attachment-0001.htm