On Thu, Sep 27, 2001 at 12:44:35AM -0500, will trillich wrote: > > debianistas tend to know where to look, so i'm hoping someone > will point the way--
sure :) > i know i've run across it before but when i WANT to stub my toe > on it, it's nowhere to be found: HOW can i have apache/web page > initiate a process and return quickly to generate a 'processing, > hold on' page while the process does its processing? > > <snip> > > pointers? flames? any gdM you think i should RTF out of? Hi Will, ...as I've seen you being active on the mod_perl list, I would've assumed that you've already heard of "The Guide" ;) Basically, there's nothing wrong with your concept of forking off the long-running process, and as a normal CGI program it would probably work fine. The few remaining flaws in it (specific to the mod_perl environment) are all detailed in the mentioned docs. So, just in case you'd like to pursue your original idea (instead of using the multipart/x-mixed-replace MIME-type method), you probably want to start reading here: http://perl.apache.org/guide/performance.html#Forking_and_Executing_Subprocess Also, if you haven't already thought of this, you might consider sending back a 'waiting'-document that automatically keeps pulling the server in certain intervals. Just include the following in the HEAD section of that html page <HTML> <HEAD> <META HTTP-EQUIV="refresh" content="5; URL=...(your URI here)"> </HEAD> ... to have it check back/reload after 5 secs. In the most simple case, the remote process you call via this URI would check whether there exists some result file (indicating that the long running process has completed), and, if so, send back the final result page, if not, resend the wait page. What also often comes in handy is the not so well known HTTP return code "Status: 204 No Content", which causes the browser to *not* update/delete its currently displayed page -- it's a kinda 'do nothing' instruction. For example, returning this 204 while the process is still running, avoids having to resend/redraw the wait-page, and the associated flickering... The above refresh technique does, however, not work in combination with the 204 trick. It would reload exactly once, as the "no content"-page cannot resend the same html code snippet, of course (and sending a real HTTP "Refresh: ..." header after the the "Status: 204" does not seem to work -- at least not with Netscape. So, for this to work, you would need a bit of javascript, something like: <HTML> <HEAD> <SCRIPT LANGUAGE="JavaScript"> function check_done() { this.location.replace("http://your.server/path/check-done.url";); } </SCRIPT> </HEAD> <BODY onLoad="setInterval('check_done()', 5000)"> Processing... Please wait... </BODY> </HTML> (the setInterval() period is in msecs) Cheers -- Erdmut Pfeifer science+computing ag www.science-computing.de -- Bugs come in through open windows. Keep Windows shut! --
