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Front end task - Predictive Load Balancing
Web server configuration example from a Well House Consultants training course
More on Web server configuration [link]
Source code: frontend Module: H305
<?php
/* This is the code to run on a single front end server for a major website that spreads a certain task over a number of back end systems (three in this example). Rather than using a standard Apache module for the balancing, we have implemented the algorithm ourselves using loading information fed back by the back end processes once they're predicted how much work will be involved in a particular task they have been passed. */ # See also http://www.wellho.net/mouth/1938_.html $servers = array("wilfred","duncan","nick"); # Look for current loadings # Algorithm applicable to first contact in a session # Alternative algorithm to be used if contact is # identified as an ongoing session. $current = array("wilfred" => 0); # Seeding mysql_pconnect("frontend","trainee","abc123"); mysql_select_db("test"); $qs = mysql_query("select size, name from actives"); while ($row = mysql_fetch_assoc($qs)) { $current[$row[name]] += $row[size]; } # Sort loadings and get lightest asort ($current); $inorder = array_keys($current); $target = $inorder[0]; # Also needed - occasional call to delete records that # are over (say) 30 seconds old from the load database # - just in case a connection is lost / back end fails # to complete. # Run the request on the appropriate backend # Need to deal with cookies, POST method, etc! $result = file_get_contents ("http://$target/action.php?$_SERVER[QUERY_STRING]"); print $result; ?> Learn about this subject
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other closely related examples on the "Web server configuration" module index page.
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