Many users at the same time

gutu · December 7th, 2013, 10:58 AM

Hello Experts
I am a teacher and I am very desparate because I wrote some educational games (wissensspiele.eu) using classic ASP on IIS2008 & SQL Server 2008. The games are used very frequently with many users at the same moment and I get many error mails every day. I stored the input of the users in session vars. And I send an email with all data to me. When I try the games with the same data I never get an error.
So I guess that I have to program another way for applications with many users in the same time.
I would be very happy to get some hints!
Greetings from Austria
Uwe

mat41 · December 8th, 2013, 04:51 AM

Hi Uwe. I can not tell what your issue is im sorry. Im not sure anybody can witht he very brief description to be honest. To get help on specific issues ideally you will need to post errors and the offending code....A couple of questions come to mind:
> What does your error mail say?
> You store all of the users input in session variables. FYI this is not efficient. ideally these should be stored in a database and carried from page to page using the request object
> 'When I try the games with the same data I never get an error' We would need to see the data....

gutu · December 8th, 2013, 04:49 PM

Thank you for your quick answer.
Yes I save all user data in the SQL Server. But my program does not reach this point and therefore I stored the user input in sessionvars to find the reason of the errors. But when I enter the same data I never get an error. So I persume that it happens only when many users are using my programs at the same second and I was asking for hints for developing ASP apps for multiuser.

The errors are different. This is only 1 example:
Error message:
Error Number: -2146828279
Error File: /bingo.asp
Line Number: 242
Index auÃerhalb des gÃ¼ltigen Bereichs: '[number: -1]' (index outside the range)
Querystring: thema=11+%2F+26&thema1=0&level=3&grad=1&checkbox1= 1&Spieler=&SpielNr=0

The relevant code:

Code:

ok = 0
  do while ok < level*level
  Dummyzahl = Int(Rnd - 89098)
  Randomize
	rec = Int((x) *Rnd + 1)										if fertig(rec-1) = 0 then			// this is line 242
			ok = ok +1
			fragen(ok,1)=alle(rec-1)
			fragen(ok,2)=typen(rec-1)
			fragen(ok,3)=0
			fragen(ok,4)=rec
			fertig(rec-1)=1
		end if
  loop

When I enter the same data I never get an error and the variable x is always 32.
So I suspect, that the variables are jumbled when many users access at the same moment.
I am desparate because when I test my programs everything works fine. But now many users are playing my games and I get a lot of error mails every day and I do not know what to do. I learned ASP 12 years ago by myself and maybe I never learned programming for many users....

Please apologisze my bad English. Thanks for your help!
Greetings from Austria
Uwe

mat41 · December 8th, 2013, 08:42 PM

mmmm I have never seen a error/post not in English. This makes things difficult. What I can tell from this:

'[number: -1]' (index outside the range)

is that it is almost definatley the 'subscript out of range' issue. If you research this you will find it simply referring to an element of the array that does not exist. So the 'rec-1' in this part of the code is your issue:

if fertig(rec-1) = 0 then

So this code:

rec = Int((x) *Rnd + 1)

is where your issue is. rec is equal to a number which does not exist in your fertig array. Hope that helps.

IMO this has nothing to do with many users at all

gutu · December 9th, 2013, 01:37 PM

Thank you Matt,

I know what the error means. But my problem is that I test the programm with the same input data and no error occurs. The variable x is always 32 and "rec" can not be -1.
The only difference is that the error occurs when many users use the game at the same moment.
So I thought that I have to know something more developing Webapps for many users. There are maybe more than 200 in the same moment when the teachers say "start the game...".

Greetings from Austria
Uwe

mat41 · December 9th, 2013, 05:26 PM

Uwe - Perhaps you don't 100% understand the error. The -1 in the error does not mean rec is equal to -1. Ignore the -1 as a value, this is not an indication of any real value for anything. Simply, the error is telling you that you are referring to an index which does not exist in your array.

You need to find out what the value of rec is when this errors. Can you send this to your email? The error is indicating this number is out of range.

What do you minus 1 from rec here?

if fertig(rec-1) = 0 then

What if the random number is at the lowest point in your range? You will get subscript out of range in this scenario.

I have not used Rnd for a while. After looking up some info it looks like you are not defining the range that the result need to fall within. It also talks about call Randomize. See borrowed information below:

Before calling Rnd, use the Randomize statement without an argument to initialize the random-number generator with a seed based on the system timer. To produce random integers in a given range, use this formula:

Int((upperbound - lowerbound + 1) * Rnd + lowerbound)

Here, upperbound is the highest number in the range, and lowerbound is the lowest number in the range.

Note To repeat sequences of random numbers, call Rnd with a negative argument immediately before using Randomize with a numeric argument. Using Randomize with the same value for number does not repeat the previous sequence.

Ok im back...In my experience a few hundred users is not all that many. I dont do anything special to cater for many more than this. Any well written application will handle this easy. IMO the number of users is irrelevant providing the application is well written