Random Distribution Code

[astro366]

Hello, I decided to randomly distribute the downloads to three servers in a 35%, 35%, 30% fashion (one server is ever so slightly inferior to the other two, so I am giving it a little less chance of getting the download). I was thinking of just generating a random number between 1 and 100, then just decide which server it should get assigned to based on which interval it falls inbetween (1-35, 36-70, 71-100). So if someone has a better way to do this/can get me started with some code fragments, I would be very grateful.

[etully]

That's not a bad solution but, as you know, when you flip a coin, it's possible to get 75 heads in a row.

If you use this method and you start to see one server overloaded, you won't know if it's because there is something wrong with that server - or if it's because the random number generator has been sending too many downloads its way.

A better way to do it is to know for sure which box is next. Since you want 35%, 35%, 30%, that's the same as a 7 : 7 : 6 ratio. In other words, Server #1 gets 7 hits, Server #2 gets 7 hits and then server #3 gets 6 hits.

So I would probably do something like this:

Write the number "0" to a table in a database. Everytime you have to make a download link, do this:

1. lock the table
2. read the number from the database into a variable called $next_server.
3. $y = $next_server + 1;
4. if ($y==20) { $y=0; }
5. write $y back to the database
6. unlock the table

Now you have $next_server which represents the next server that should be used. So set up an array like this:

$a = array(1,2,3,1,2,3,1,2,3,1,2,3,1,2,3,1,2,3,1,2);
$link = "http://www" . $a[$next_server] . ".yourdomain.com/files/music.mp3";

(this assumes that your servers are called www1.yourdomain.com, www2, and www3). You could also set $link like this:

if ($a[$next_server]==1) { $link = "http://www.happy.com/downloads/mp3/music.mp3"; }
if ($a[$next_server]==2) { $link = "http://www.golucky.com/mp3/music.mp3"; }
if ($a[$next_server]==3) { $link = "http://www.flippy.com/music_archive/music.mp3"; }

Notice that there are only 20 records in the array, That's 7+7+6 = 20.

This way, you will spread the downloads across the 3 servers in a 7:7:6 ratio

[astro366]

Thank you for the help. Just wondering, its possible to have the filename specified by the URL you click on to activate the script? like $FILE = "something in the URL" then $link = "http://www.server.com/music_archive/$FILE";

[etully]

Yes. You can pass a variable in a URL like this:

http://www.yourdomain.com/random_distribution_script.php?file=prince-1999.mp3

or like this:

http://www.yourdomain.com/random_distribution_script.php?file=1

If you use the first URL, then the distribution script will know exactly what file the user wants to see and you can build the link like this:
$link = "http://www" . $a[$next_server] . ".yourdomain.com/files/" . $_GET['file'] ;

Sometimes you don't want to put the file NAME in the URL like that. You can see in the URL that the variable "$file" is getting passed in with a value of "1". You can use that information to determine which file they should see like this:

if ($GET['$file']==1) { $filename = "prince-1999.mp3"; }
if ($GET['$file']==2) { $filename = "rolling-stones-satisfaction.mp3"; }

And then create the link like this:
$link = "http://www" . $a[$next_server] . ".yourdomain.com/files/" . $filename;

[astro366]

So $_GET['file'] stores the name of the file after the "?file="? And in the first post where you said to lock the table, would a read or write lock be better? Thanks.