This is mainly in response to the longstanding issue #36 in which my
proposed solution was fine in terms of functionalities, but eventually
never made into the repository since it was far from being clean enough
for my taste.
Now developers can optionally pass a callable object when creating the
hashring instance to decide how the distributor should extract the hash
from a node (really a connection instance) to populate the ring:
use Predis\Cluster\Distribution\HashRing;
use Predis\Connection\PredisCluster;
$servers = array(
'tcp://10.0.0.1?alias=node01',
'tcp://10.0.0.2?alias=node02',
);
$options = array(
'nodehash' => function ($connection) {
return $connection->getParameters()->alias;
},
'cluster' => function ($options) {
$replicas = HashRing::DEFAULT_REPLICAS;
$hashring = new HashRing($replicas, $options->nodehash);
$cluster = new PredisCluster($hashring);
return $cluster;
},
);
$client = new Predis\Client($servers, $options);
Both HashRing and KetamaPureRing in the Predis\Cluster\Distribution
namespace support this new approach.
We extract the keys from commands using the second argument of EVAL /
EVALSHA which specifies the number of arguments that must be treated
as keys (used to populate the KEYS table in the Lua script) and then
we check if there is only one key since redis-cluster right now does
not support multi-keys requests.
Our scripted command abstraction is also supported.
We extract the keys from commands using the second argument of EVAL /
EVALSHA which specifies the number of arguments that must be treated
as keys (used to populate the KEYS table in the Lua script) and then
we check if all the keys generate the same hash using the usual method.
Our scripted command abstraction is also supported.
It comes without saying that accessing or setting keys from within the
Lua script is something that might not work as expected, so you should
be careful when using EVAL and EVALSHA in the context of client-side
sharding.
Daniele Alessandri