Reentrant POST

[a]

Hi,

I have the following setup: PHP 5.1.x on Apache 2.x on Windows XP.

A php script receives data from a form upon user submit, and then execs a
Windows process, which may take some time to complete (actually this process
performs a quite complex task which involves starting another process and
then requesting a Windows service to perform yet other tasks). Everything
works fine as long as the user submits the form and then patiently waits for
the processing to end. However, if the user clicks on submit while the php
script is still waiting for the windows process to end, than the browser
will remain in this state indefinitely, the Windows processes never complete
their tasks and sometimes Apache crashes.

Is there a way to handle this so the work in progress is either allowed to
end or instructed to stop, before moving on to processing the new submit?

Thanks,

A

[Colin McKinnon]

a wrote:

Is there a way to handle this so the work in progress is either allowed to
end or instructed to stop, before moving on to processing the new submit?

I think you've misunderstood the meaning of 'reentrant'.

Interfering with the existing process is not trivial. Wouldn't it be simpler
to not allow the user to POST more than once - something like:

<input type='button' id='submitId' onclick='
if (document.getElementById("formId").onsubmit()) {
document.getElementById("submitId").disabled=true;
document.getElementById("formId").submit();
}' value='Submit'>

C.

[a]

Thanks for your reply.

I think you've misunderstood the meaning of 'reentrant'.

By "reentrant" I meant that the user would POST while a previous POST is
still being processed on the server.
Interfering with the existing process is not trivial. Wouldn't it be
simpler
to not allow the user to POST more than once - something like:

<input type='button' id='submitId' onclick='
if (document.getElementById("formId").onsubmit()) {
document.getElementById("submitId").disabled=true;
document.getElementById("formId").submit();
}' value='Submit'>

Yes, this would prevent the user from resubmitting a form, but there is also
the issue of allowing the user to cancel a lengthy processing, in which case
a new post would still have to be sent.

I'm leaning now more toward an asynchronous solution in which the windows
process that is exec-ed by the php script starts another process to do the
actual work and then returns immediately, allowing the php script to
continue. There will have to be a synchronization mechanism between the
working process and the php script that will signal when the data is ready,
or will allow the processing to be canceled.

A