Weighted Load Balancing Algorithm into PHP Application - php

Question

I want to resolve weighted an Adapter from an factory which could be configured by user (enable/disable and weight %).
Example:
AdapterW ≃ 20% of transaction
AdapterX ≃ 30% of transaction
AdapterY ≃ 40% of transaction
AdapterZ ≃ 10% of transaction
I can grant that all items will never sum more than one hundred (100%), but sometimes any adapter could be deactivated.
I have the following parameters:
public function handleAdapter()
{
$isWActive = (boolean)$this->_config[self::W];
$isXActive = (boolean)$this->_config[self::X];
$isYActive = (boolean)$this->_config[self::Y];
$isZActive = (boolean)$this->_config[self::Z];
$WPercentage = (int)$this->_config[self::LOAD_BALANCE_W];
$XPercentage = (int)$this->_config[self::LOAD_BALANCE_X];
$YPercentage = (int)$this->_config[self::LOAD_BALANCE_Y];
$ZPercentage = (int)$this->_config[self::LOAD_BALANCE_Z];
.
.
.
return (self::W | self::X | self::Y | self::Z);
}
How can i balance weighted between this adapters dynamically?
Edit
created a gist to a executable code: https://gist.github.com/markomafs/5d892d06d6670909f9b4

Answer 1

This may not be the best approach, but you can try something like this:
public function handleAdapter()
{
//an array to return the balanced entries
$balancedEntries[] = false;
//verifies which of the options are active
$isWActive = (boolean)$this->_config[self::W];
$isXActive = (boolean)$this->_config[self::X];
$isYActive = (boolean)$this->_config[self::Y];
$isZActive = (boolean)$this->_config[self::Z];
//get configured percentage of each
$WPercentage = (int)$this->_config[self::LOAD_BALANCE_W];
$XPercentage = (int)$this->_config[self::LOAD_BALANCE_X];
$YPercentage = (int)$this->_config[self::LOAD_BALANCE_Y];
$ZPercentage = (int)$this->_config[self::LOAD_BALANCE_Z];
//here you fill the array according to the proportion defined by the percentages
if ($isWActive) {
for ($i = 0; $i < $WPercentage; $i++) {
$balancedEntries[] = self::W;
}
}
if ($isXActive) {
for ($i = 0; $i < $XPercentage; $i++) {
$balancedEntries[] = self::X;
}
}
if ($isYActive) {
for ($i = 0; $i < $YPercentage; $i++) {
$balancedEntries[] = self::Y;
}
}
if ($isZActive) {
for ($i = 0; $i < $ZPercentage; $i++) {
$balancedEntries[] = self::Z;
}
}
return $balancedEntries;
}
And then, in case you want a proportion of 1 to 100 (as in percentages):
$balancedResult = $balancedEntries[array_rand($balancedEntries, 1)];
Since array_rand will return 1 key from the original array, you use it to get it's value.

Answer 2

Another try, this should work for your case - But it only work if you have an adapter as a single char string, this is not visible by your question.
public function handleAdapter()
{
# a map with all adapters
$map = array(
self::W => self::LOAD_BALANCE_W,
self::X => self::LOAD_BALANCE_X,
self::Y => self::LOAD_BALANCE_Y,
self::Z => self::LOAD_BALANCE_Z
);
# generate a string map with one char per percentage point
$stringMap = "";
foreach($map as $key => $value){
# skip if disabled
if(!$this->_config[$key]) continue;
# repeat the key for each percentage point
$stringMap .= str_repeat($key, (int)$this->_config[$value]);
}
# return a random string char from the map
return $stringMap[rand(0, strlen($stringMap) - 1)];
}

Answer 3

Edit: I've misunderstood the question, the answer is wrong.
I understand your question so that you always want to return the adapter with the lowest load to force traffic to this adapter.
public function handleAdapter()
{
$isWActive = (boolean)$this->_config[self::W];
$isXActive = (boolean)$this->_config[self::X];
$isYActive = (boolean)$this->_config[self::Y];
$isZActive = (boolean)$this->_config[self::Z];
$WPercentage = (int)$this->_config[self::LOAD_BALANCE_W];
$XPercentage = (int)$this->_config[self::LOAD_BALANCE_X];
$YPercentage = (int)$this->_config[self::LOAD_BALANCE_Y];
$ZPercentage = (int)$this->_config[self::LOAD_BALANCE_Z];
$map = array();
if($isWActive) $map[self::W] = $WPercentage;
if($isXActive) $map[self::X] = $XPercentage;
if($isYActive) $map[self::Y] = $YPercentage;
if($isZActive) $map[self::Z] = $ZPercentage;
asort($map);
return key($map);
}
Edit: Fixed wrong sort(), you need asort() to maintain the index.