I think we can indeed start promoting Predis\Async now that it has
reached a fairly stable state (in terms of API and functionalites)
despite still being considered experimental.
[ci skip]
Multibulk response iterators will not be passed anymore to the response
parser method of the command that generated the response. Pipeline and
transaction abstractions still consume interators returned as response
items.
When no server profile is specified, the connection factory will not push
any initialization command to the newly created connection object.
This change is mainly useful when using redis-cluster and also makes it
possible to easily inject commands such as "SCRIPT LOAD" at initialization
time by grouping everything into one common place simply by extending the
connection factory class.
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.
This should make things a tiny bit faster (we are speaking about micro
optimizations anyway) but more importantly it results in a better
encapsulation.
This makes it possible to easily assign a connection to a slot range
using the key "slots" in connection parameters like in the following
example:
$parameters = array(
'tcp://127.0.0.1:6379?slots=0-1364',
'tcp://127.0.0.1:6380?slots=1365-2729',
'tcp://127.0.0.1:6381?slots=2730-4095',
);
$options = array('cluster' => 'redis');
$client = new Predis\Client($parameters, $options);
It is possible to get the full list of slot ranges for each node of
the cluster using redis-cli connected to one of the nodes:
./redis-cli -h 127.0.0.1 -p 6379 CLUSTER NODES
The last column in the resulting output contains the slots assigned
to each instance participating to the redis cluster.
This is useful to avoid guessing the correct server instance at runtime
thus reducing the overhead of a guess-and-try approach since relying on
-ASK or -MOVED responses returned by a node is a costly operation.
For now, you can pre-associate slots using the "cluster" client option:
$parameters = array(
'tcp://127.0.0.1:6379',
'tcp://127.0.0.1:6380',
'tcp://127.0.0.1:6381',
);
$options = array(
'cluster' => function ($options) {
$cluster = new Predis\Connection\RedisCluster();
$cluster->setSlots(0, 1364, '127.0.0.1:6379');
$cluster->setSlots(1365, 2729, '127.0.0.1:6380');
$cluster->setSlots(2730, 4095, '127.0.0.1:6381');
return $cluster;
},
);
$client = new Predis\Client($parameters, $options);
In the future we will make the slots configuration easier by fetching
the configuration from a node using the command "CLUSTER NODES" or by
pre-computing the slices of slots associated to a node when adding it
to the cluster connection object.
This is needed because redis-cluster does not support the same commands
or operations that can be performed with our client-side managed predis
cluster.
For example redis-cluster does not support key tagging (that is, parts
of a key enclosed by {...} to hash only that specific part of a key)
and multiple-key operations suchs as MGET, MSET, SDIFF, SUNION or SINTER.
Some multiple-key operations can be performed anyway if the command has
only one key (e.g. "MGET foo" and "MSET foo bar" will not fail).
Daniele Alessandri
Pascal Borreli