is it possible to flush data to the screen from inside an as cfml #cfml-general

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is it possible to flush data to the screen from in...

# cfml-general

Scott Steinbeck

03/09/2023, 11:46 PM

is it possible to flush data to the screen from inside an async loop?

Adam Cameron

03/10/2023, 12:30 AM

You might be able to pass the output buffer thingey (possibly not its actual name) from the

PageContext

object into yer async code and append to it? @bdw429s didn't we look at something like this before, a few months ago? Not sure where we got to, and it's 00:30 here (only just noticed this), so I'm going to bed instead of looking further...

bdw429s

03/10/2023, 6:37 AM

If you can write output to the main page from an async loop, I would assume you can flush that output. I saw the question, but didn't reply myself because I didn't have time to actually go test it right then, and it seems @Scott Steinbeck could also just test it himself and then come back and tell us what the answer is 🙂

bdw429s

03/10/2023, 6:38 AM

It's also not quite clear just what sort of "async loop" he's talking about. (I can think of several things that he could mean)

bdw429s

03/10/2023, 6:45 AM

At first blush, this approach does NOT work.

Copy code

echo( 'start<br>' )
flush;
[1,2,3,4,5].each( (i)=>{
    sleep( randRange( 1, 5000 ) )
    echo( 'Iteration #i#<br>' )
    flush;
}, true );

bdw429s

03/10/2023, 6:46 AM

When not async, you get the output flushed as it goes, but once you make it async, it seems Lucee waits until the entire each() is done before anything gets output

Scott Steinbeck

03/10/2023, 6:47 AM

That was my experience as well, but I just assumed I was doing something wrong. My scenario is exactly like your example

bdw429s

03/10/2023, 6:48 AM

This version seems to work OK

Copy code

responseStream = getPageContext().getResponseStream();
echo( 'start<br>' )
flush;
[1,2,3,4,5].each( (i)=>{
    sleep( randRange( 1, 5000 ) )
    responseStream.print( 'Iteration #i#<br>' )
    responseStream.flush()
}, true );

bdw429s

03/10/2023, 6:49 AM

The outputs come up in the browser as they happen in a random order

bdw429s

03/10/2023, 6:49 AM

I'd put in a ticket

bdw429s

03/10/2023, 6:50 AM

@Scott Steinbeck

Scott Steinbeck

03/10/2023, 6:51 AM

I’ll add one in the morning, I’m headed to bed. Thanks for providing a workaround