[R] Closing FTP sessions with RCurl

[William Dunlap]

>>    rm(curl) # release the curl! (does this end the session???)

Try adding a call to gc() immediately after this removal.  That will force
an
immediate run of any finalizer associated with the object just removed.
With the call to gc(), the garbage collector will be called some time in the
future and the finalizers will be run then.

(I don't know if curl has a finalizer that closes the session.)


Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Wed, Jun 15, 2016 at 12:34 PM, J Payne <jcpayne at uw.edu> wrote:

> Thanks Tom!  I tried that and it didn’t work, but perhaps there are other
> problems.  The system administrator wrote “I think closing sessions
> immediately upon completion of the transfer,
> or continuing to use the same session for additional requests would both
> have a similar and positive effect.”  However, I’ve now tried your solution
> to close the session, and also tried using one curl handle throughout, but
> the throttling persists.
>
> John
>
> On 6/14/16, 1:00 PM, "Tom Wright" <tom at maladmin.com> wrote:
>
> >No expert here, and this isn't tested. It seems you can set the
> >forbid.reuse option which will cause curl to shutdown the connection
> >after transfer is complete.
> >
> >if(url.exists("http://www.omegahat.net/RCurl/index.html")) {
> >   curl <- getCurlHandle()
> >   curlSetOpt(.opts=list(forbid.reuse=1),curl=curl)
> >   getURL("http://www.omegahat.net/RCurl/index.html", curl = curl)
> >}
> >
> >On Tue, Jun 14, 2016 at 2:41 PM, J Payne <jcpayne at uw.edu> wrote:
> >> Does anyone know how to close an FTP session with RCurl?  I am trying
> to automate the process of downloading snow data from a government website,
> and their server is throttling the connection after a few files are
> downloaded.  I contacted their system administrator, who wrote: “My
> suspicion at this point is that the getURL commands are opened and perform
> the function asked, then linger in wait for 15 minutes until or ftp server
> closes the idle sessions. Is there a way to tell R to close the sessions?”
> >>
> >>
> >>
> >> I’ve perused the RCurl manual but I don’t see a way to close sessions.
> I tried copying the following example from the RCurl manual, but it didn’t
> solve the problem.  I’m a novice at this and I don’t understand the
> relationship between handles and sessions, so I am probably missing
> something.
> >>
> >>
> >>
> >> #EXAMPLE from getCurl(), p. 39
> >>
> >> if(url.exists("http://www.omegahat.net/RCurl/index.html")) {
> >>
> >>    curl = getCurlHandle()
> >>
> >>    getURL("http://www.omegahat.net/RCurl/index.html", curl = curl)
> >>
> >>    #getCurlInfo(curl) # I skipped this step
> >>
> >>    rm(curl) # release the curl! (does this end the session???)
> >>
> >> }
> >>
> >>
> >>
> >> Thanks!
> >>
> >>
> >>
> >> John
> >>
> >>
> >>         [[alternative HTML version deleted]]
> >>
> >> ______________________________________________
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> >> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

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