*/
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, 'watch' => $key, 'retry' => 3);
$client->transaction($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;
require_once 'SharedConfigurations.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
ZADD zset 2 b
ZADD zset 3 c
*/
function zpop($client, $zsetKey)
{
$element = null;
$options = array('cas' => true, 'watch' => $zsetKey, 'retry' => 3);
$txReply = $client->multiExec($options, function ($tx) use($zsetKey, &$element) {
@(list($element) = $tx->zrange($zsetKey, 0, 0));
if (isset($element)) {
$tx->multi();
// With CAS, MULTI *must* be explicitly invoked.
$tx->zrem($zsetKey, $element);
}
});
return $element;
}
$redis = new Predis\Client($single_server, 'dev');
$zpopped = zpop($redis, 'zset');
echo isset($zpopped) ? "ZPOPed {$zpopped}" : "Nothing to ZPOP!", "\n";
