[Zope] Display status updates/preventing timeouts during long operation

[Passin, Tom]

[ Robert McPeak]
>=20
> I've got an external method that performs some manipulations=20
> on a CSV file
> that the user uploads to my zope site.  Processing of each=20
> line of the CSV
> file takes up to 1 second (I'm querying some external=20
> systems, among other
> things).  These user-uploaded files can contain several=20
> thousand lines, and
> timeouts are happening before the data processing is completed.
>=20
> How can I change the process to report status and prevent=20
> timeouts?  The
> user is not going to like looking at a blank page for hours=20
> on end...I don't
> either, for that matter. :)
>=20

You should change the concept of operations of the process.  You should
not try to keep a connection to the user's browser open for such a
length of time.  This ties up resources and may prevent the user from
using her browser for other things.  Also, with only a few requests you
could easily bring your server to its knees for lack of threads.

You can try to use HTTP methods, or change completely.  Here are some
possibilities -

1) Have your server email the results to the user when they are ready.
2) Process teh data off-line, and use the 202 (Accepted) HTTP status
code, which seems to be designed for this kind of processing. Here is
the definition of this status code, from  RFC 2616 -

"202 Accepted

The request has been accepted for processing, but the processing has not
been completed. The request might or might not eventually be acted upon,
as it might be disallowed when processing actually takes place. There is
no facility for re-sending a status code from an asynchronous operation
such as this.

The 202 response is intentionally non-committal. Its purpose is to allow
a server to accept a request for some other process (perhaps a
batch-oriented process that is only run once per day) without requiring
that the user agent's connection to the server persist until the process
is completed. The entity returned with this response SHOULD include an
indication of the request's current status and either a pointer to a
status monitor or some estimate of when the user can expect the request
to be fulfilled. "

Cheers,

Tom P