concurrent users

[Duane Pederson]

Evening

I have code on an a5w page that opens an img ref photo, opens a table to get another photo, grabs another photo from the root, and merges these 3 photos together, then saves the result jpg in a folder named after a piece of data in the original photo's table. The resulting photo path and filename are saved in another table, then a grid displays these photos.

This code loops through a table 29 more times to make and save more photos.
It seems to take 12 - 15 seconds to complete the procedure and display the grid.

This procedure works very well

Unless 2 or more users are doing this at the same time
Some of the images from the subsequent user are being placed in the first users records. And they aren't happy.

Obviously I don't know how to keep users separated in this web stuff

Any ideas on what I'm missing?

Thanks
Duane

[ColinJD]

Re: concurrent users

Obviously I don't know how to keep users separated in this web stuff

Who does Duane, who does.
-
I have a similar process on a site to what you have, but know where near as complex.
A. I make use of each users session folder, not only does this remain separate but the App server cleans it up when the session expires.
B. Always remember that the App-Server runs basically in a stateless manner, eg it remembers zilch from the last code page run, Thus you need to write stuff into temp tables or files or special server or session vars, if you wish to refer to it later.

Unless 2 or more users are doing this at the same time

-
In writing this, I would look at keeping everything on one code page.
I'm not 100% on this but I believe the AppServer only processes one page at a time, thus, the 2nd user would have a short wait. Also make sure that the session variables are not at all shared.

[Steve Wood]

Re: concurrent users

Every user on your website has a unique folder belonging only to them. The name of the folder is in the variable session._session_folder. If you perform your process using that as the work area, everything will stay separate. When their session expires, the folder and contents will disappear.

Also, when it comes to images, you might look at ImageMagik. It can process images with command line tools, to do just about anything. The HELP for ImageMagik is awful, but here is an example that uploads an image, and in the last stage creates PNG thumbnails using ImageMagik.

'session.mod = mod

dim session.im1 as c
if eval_valid("cmd")
	if file.exists(fldr) = .f.
		file.dir_create_recurse(fldr)
	end if
	IF FileToUpload.filename<>""
		filename = fldr + "\\" + FileToUpload.filename
		if file.exists(filename)
			file.remove(filename)
		end if
		newfilename = fldr + "\\" + session.id + ".jpg"
		if file.exists(newfilename)
			file.remove(newfilename)
		end if

		newthumb	= fldr + "\\" + "th_"+session.id + ".png"
		file.from_blob(filename,FileToUpload.data)
		file.rename(filename,newfilename)

		'CREATE THUMB
		shelltask = fldr + "\mk.bat " + fldr + " " + session.id + " " + "" 
		sys_shell_wait(shelltask)
		im = path + "\\" + "th_"+session.id+".png"
else
?"No file to upload"
	end if
end if
%>

The MK.BAT looks like this:

c:\progra~1\imagem~1\convert.exe %1\%2.jpg -auto-orient -thumbnail 200 -unsharp 0x.5 %1\th_%2.png

[Duane Pederson]

Re: concurrent users

Thanks for the replies guys

Deep down inside I knew I should be playing with session folders. I had to do that once before using javascript to keep photos organized between clients. But this time I was kinda foggy and wasn't sure how to procede with that, so the method I took was faster to me.

And now I'm paying the price.

I have the routine's code on one page and as a precaution I'm trying to use a variable = t and f to let people through the code or to wait and check the variable value again (doesn't seem to work very well). I don't think any of these session variables are shared, although I'm not really sure how to share them or not to.

I will have to design it properly when I can get to it in a few months and hope not too many clients have photos colliding in the mean time.

Steve, thanks for the IM code. Been looking at that pgm for another purpose for a while trying to get it figured out. Never thought about using it for this web purpose. Probably would have been better since it wouldn't be using the A5 blob variable bitmap confusing way that I have been. There wouldn't be any blobs getting mixed up between clients, I figure that is what has been happening - the blobs are getting replaced by the newer request.

Thanks
Duane