53 lines
1.5 KiB
PHP
53 lines
1.5 KiB
PHP
<?php
|
|
|
|
/*
|
|
* This file is part of the Predis package.
|
|
*
|
|
* (c) Daniele Alessandri <suppakilla@gmail.com>
|
|
*
|
|
* For the full copyright and license information, please view the LICENSE
|
|
* file that was distributed with this source code.
|
|
*/
|
|
|
|
require __DIR__.'/shared.php';
|
|
|
|
// This is an implementation of an atomic client-side ZPOP using the support for
|
|
// check-and-set (CAS) operations with MULTI/EXEC transactions, as described in
|
|
// "WATCH explained" from http://redis.io/topics/transactions
|
|
//
|
|
// First, populate your database with a tiny sample data set:
|
|
//
|
|
// ./redis-cli
|
|
// SELECT 15
|
|
// ZADD zset 1 a 2 b 3 c
|
|
//
|
|
// Then execute this script four times and see its output.
|
|
//
|
|
|
|
function zpop($client, $key)
|
|
{
|
|
$element = null;
|
|
$options = array(
|
|
'cas' => true, // Initialize with support for CAS operations
|
|
'watch' => $key, // Key that needs to be WATCHed to detect changes
|
|
'retry' => 3, // Number of retries on aborted transactions, after
|
|
// which the client bails out with an exception.
|
|
);
|
|
|
|
$client->transaction($options, function ($tx) use ($key, &$element) {
|
|
@list($element) = $tx->zrange($key, 0, 0);
|
|
|
|
if (isset($element)) {
|
|
$tx->multi(); // With CAS, MULTI *must* be explicitly invoked.
|
|
$tx->zrem($key, $element);
|
|
}
|
|
});
|
|
|
|
return $element;
|
|
}
|
|
|
|
$client = new Predis\Client($single_server);
|
|
$zpopped = zpop($client, 'zset');
|
|
|
|
echo isset($zpopped) ? "ZPOPed $zpopped" : 'Nothing to ZPOP!', PHP_EOL;
|