Workflow CGITask - How to print immediately from perl script

Hello -
ENV - Teamsite 7.3.1 on redhat.

I have a cgitask that does some stuff for about 2 minutes.

I want to print status of what its upto, while its busy doing its thing.

I tested locally on an apache webserver, using a simple perl script. If I print something, it shows up on the browser right away.

But when I run a perl script as a cgitask, it waits for the whole perl script to finish, before displaying all the output. I'm aware that the perl script (cgitask) is wrapped by the iw_cgi_wrapper.cgi etc. Is that why ? Is there a way to print stuff to the browser immediately?

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Comments

Adam Stoller

Without seeing your code - it's difficult to tell what may be happening, but the first thing that comes to mind is to ask whether you explicitly set the CGI Perl script to not buffer STDOUT (by default, it is buffered)

ISCBorisB

Is there a way to print stuff to the browser immediately?

Wrapper has nothing to do to the problem. It impersonates Task owner, that's it.

Your issue illustrates an essential aspect (weakness?) of CGI Protocol. Without undue details, single CGI request
renders back single Page, that's it. So, to show status dynamically you will have to code multiple server requests,
not necessarily CGIs.

For example, you may return Page output immediately leaving the actual data part as an empty <div> element.
Then you can update the content of that element with javascript via AJAX requests, showing progress, etc...

Alternatively, you may (again immediately!) render framed Page with one Frame showing (or faking) some activity like
status bar image and the actual Frame (hidden perhaps) executing "actual" CGI to get data.

Finally, you can render a Page that in turn executes multiple CGI requests. This is named "Client Pull", here is a good sample.

Jashan

Without seeing your code - it's difficult to tell what may be happening, but the first thing that comes to mind is to ask whether you explicitly set the CGI Perl script to not buffer STDOUT (by default, it is buffered)

This is the first line in the script to output right away....
"# Flush the output buffer right away.
$| = 1;

Attached file is the standard "sample_cgi_task.ipl", to be used as the cgitask command. Look for "write_header" call. I put in a sleep for 10 secs right after it. In my case, the browser doesnt display anything until it has finished the entire script.

Adam Stoller

Okay - then I suggest you read / re-read Boris' response - which is much more detailed about ways to overcome the way in which CGI's render their content.