7c4198805a
Also factor out consistent hash code from Redis and the new application into a class called ArrayUtils. The name "ArrayUtils" is from I0f4e7d7c, I expect that change will be rebased on top of this one at some point. Change-Id: I9375087f4d7a6e8e629d97bfb6b117d9cb7d1bcf
34 lines
1.2 KiB
PHP
34 lines
1.2 KiB
PHP
<?php
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class ArrayUtils {
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/**
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* Sort the given array in a pseudo-random order which depends only on the
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* given key and each element value. This is typically used for load
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* balancing between servers each with a local cache.
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*
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* Keys are preserved. The input array is modified in place.
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*
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* Note: Benchmarking on PHP 5.3 and 5.4 indicates that for small
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* strings, md5() is only 10% slower than hash('joaat',...) etc.,
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* since the function call overhead dominates. So there's not much
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* justification for breaking compatibility with installations
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* compiled with ./configure --disable-hash.
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*
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* @param $array The array to sort
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* @param $key The string key
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* @param $separator A separator used to delimit the array elements and the
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* key. This can be chosen to provide backwards compatibility with
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* various consistent hash implementations that existed before this
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* function was introduced.
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*/
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static function consistentHashSort( &$array, $key, $separator = "\000" ) {
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$hashes = array();
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foreach ( $array as $elt ) {
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$hashes[$elt] = md5( $elt . $separator . $key );
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}
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uasort( $array, function ( $a, $b ) use ( $hashes ) {
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return strcmp( $hashes[$a], $hashes[$b] );
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} );
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}
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}
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