rediscluster-php

a PHP interface to a Cluster of Redis key-value stores.

Project Goals

The goal of rediscluster-php, together with rediscluster-py, is to have a consistent, compatible client libraries accross programming languages when sharding among different Redis instances in a transparent, fast, and fault tolerant way. rediscluster-php uses phpredis when connecting to the redis servers, thus the original api commands would work without problems within the context of a cluster of redis servers.

Continuous Integration

Currently, rediscluster-php is being tested via travis/drone.io ci for php version 5.3 and 5.4:

Installation

Download via Composer Create a composer.json file if you don't already have one in your projects root directory and require rediscluster:

{
  "require": {
    "rediscluster/rediscluster": "0.5.*"
  }
}

Install Composer:

$ curl -s http://getcomposer.org/installer | php

Run the install command:

$ php composer.phar install

This will download rediscluster into the vendor/rediscluster/rediscluster directory. To learn more about Composer visit http://getcomposer.org/

Running Tests

$ git clone https://github.com/salimane/rediscluster-php.git
$ cd rediscluster-php
$ vi Tests/config.php
$ phpunit

Getting Started

php -a
Interactive shell

php > require "/home/salimane/htdocs/rediscluster-php/vendor/autoload.php";
php > $cluster = array(
php (     //node names
php (     'nodes' => array(
php (       //masters
php (       'node_1' => array('host' => '127.0.0.1', 'port' => 63791),
php (       'node_2' => array('host' => '127.0.0.1', 'port' => 63792),
php (     )
php ( );
php >
php > $r = new RedisCluster\RedisCluster($cluster, 4);
php > var_dump($r->set('foo', 'bar'));
bool(true)
php > var_dump($r->get('foo'));
string(3) "bar"

Cluster Configuration

The cluster configuration is a hash that is mostly based on the idea of a node, which is simply a host:port pair that points to a single redis-server instance. This is to make sure it doesn’t get tied it to a specific host (or port). The advantage of this is that it is easy to add or remove nodes from the system to adjust the capacity while the system is running.

Read Slaves & Write Masters

rediscluster, by default, uses the master servers stored in the cluster hash passed during instantiation to auto discover if any slave is attached to them. It then transparently relay read redis commands to slaves and writes commands to masters.

There is also support to only use masters even if read redis commands are issued, just specify it at client instantiation like :

php > $r = new RedisCluster\RedisCluster($cluster, 4); // read redis commands are routed to slaves
...
php > $r = new RedisCluster\RedisCluster($cluster, 4, true); // read redis commands are routed to masters
...

Partitioning Algorithm

In order to map every given key to the appropriate Redis node, the algorithm used, based on crc32 and modulo, is :

((abs(crc32(<key>)) % <number of masters>) + 1)

A function getnodefor is provided to get the node a particular key will be/has been stored to.

php > print_r($r->getnodefor('foo'));
Array
(
    [node_2] => Array
        (
            [host] => 127.0.0.1
            [port] => 63792
        )

)
php >

Hash Tags

In order to specify your own hash key (so that related keys can all land on a given node), rediscluster allows you to pass a string in the form "a{b}" where you’d normally pass a scalar. The first element of the list is the key to use for the hash and the second is the real key that should be fetched/modify:

php > $r->get("bar{foo}")
...
php > $r->mset(array("bar{foo}" => "bar", "foo" => "foo"))
...
php > $r->mget(array("bar{foo}", "foo"))

In that case “foo” is the hash key but “bar” is still the name of the key that is fetched from the redis node that “foo” hashes to.

Multiple Keys Redis Commands

In the context of storing an application data accross many redis servers, commands taking multiple keys as arguments are harder to use since, if the two keys will hash to two different instances, the operation can not be performed. Fortunately, rediscluster is a little fault tolerant in that it still fetches the right result for those multi keys operations as far as the client is concerned. To do so it processes the related involved redis servers at interface level.

php > foreach(array('b1', 'a2', 'b3') as $i) $r->sadd('bar', $i);
php > foreach(array('a1', 'a2', 'a3') as $i) $r->sadd('foo', $i);
php > var_dump($r->sdiffstore('foobar', 'foo', 'bar'));
int(2)
php >
php > print_r($r->smembers('foobar'));
Array
(
    [0] => a1
    [1] => a3
)
php >
php > print_r($r->getnodefor('foo'));
Array
(
    [node_2] => Array
        (
            [host] => 127.0.0.1
            [port] => 63792
        )

)
php > print_r($r->getnodefor('bar'));
Array
(
    [node_1] => Array
        (
            [host] => 127.0.0.1
            [port] => 63791
        )

)
php > print_r($r->getnodefor('foobar'));
Array
(
    [node_2] => Array
        (
            [host] => 127.0.0.1
            [port] => 63792
        )

)
php >

Redis-Sharding & Redis-Copy

In order to help with moving an application with a single redis server to a cluster of redis servers that could take advantage of rediscluster, i wrote redis-sharding and redis-copy

Information

• Code: git clone git://github.com/salimane/rediscluster-php.git
• Home: http://github.com/salimane/rediscluster-php
• Bugs: http://github.com/salimane/rediscluster-php/issues

Author

rediscluster-php is developed and maintained by Salimane Adjao Moustapha ([email protected]). It can be found here: http://github.com/salimane/rediscluster-php