Cluster.php

<?php

/**
 * Credis, a Redis interface for the modest
 *
 * @author Justin Poliey <jdp34@njit.edu>
 * @copyright 2009 Justin Poliey <jdp34@njit.edu>
 * @license http://www.opensource.org/licenses/mit-license.php The MIT License
 * @package Credis
 */

/**
 * A generalized Credis_Client interface for a cluster of Redis servers
 *
 * @deprecated
 */
class Credis_Cluster
{
    /**
     * Number of replicas for each server in the cluster
     * @var int
     */
    protected $replicas;
    /**
     * Collection of Credis_Client objects attached to Redis servers
     * @var Credis_Client[]
     */
    protected $clients;
    /**
     * If a server is set as master, all write commands go to that one
     * @var Credis_Client
     */
    protected $masterClient;
    /**
     * Aliases of Credis_Client objects attached to Redis servers, used to route commands to specific servers
     * @see Credis_Cluster::to
     * @var array
     */
    protected $aliases;

    /**
     * Hash ring of Redis server nodes
     * @var array
     */
    protected $ring;

    /**
     * Individual nodes of pointers to Redis servers on the hash ring
     * @var array
     */
    protected $nodes;

    /**
     * The commands that are not subject to hashing
     * @var array
     * @access protected
     */
    protected $dont_hash;

    /**
     * Currently working cluster-wide database number.
     * @var int
     */
    protected $selectedDb = 0;

    /**
     * Creates an interface to a cluster of Redis servers
     * Each server should be in the format:
     *  array(
     *   'host' => hostname,
     *   'port' => port,
     *   'db' => db,
     *   'password' => password,
     *   'timeout' => timeout,
     *   'alias' => alias,
     *   'persistent' => persistence_identifier,
     *   'master' => master
     *   'write_only'=> true/false
     * )
     *
     * @param array $servers The Redis servers in the cluster.
     * @param int $replicas
     * @param bool $standAlone
     * @throws CredisException
     */
    public function __construct($servers, $replicas = 128, $standAlone = false)
    {
        $this->clients = array();
        $this->masterClient = null;
        $this->aliases = array();
        $this->ring = array();
        $this->replicas = (int)$replicas;
        $client = null;
        foreach ($servers as $server) {
            if (is_array($server)) {
                $client = new Credis_Client(
                    $server['host'],
                    $server['port'],
                    isset($server['timeout']) ? $server['timeout'] : 2.5,
                    isset($server['persistent']) ? $server['persistent'] : '',
                    isset($server['db']) ? $server['db'] : 0,
                    isset($server['password']) ? $server['password'] : null
                );
                if (isset($server['alias'])) {
                    $this->aliases[$server['alias']] = $client;
                }
                if (isset($server['master']) && $server['master'] === true) {
                    $this->masterClient = $client;
                    if (isset($server['write_only']) && $server['write_only'] === true) {
                        continue;
                    }
                }
            } elseif ($server instanceof Credis_Client) {
                $client = $server;
            } else {
                throw new CredisException('Server should either be an array or an instance of Credis_Client');
            }
            if ($standAlone) {
                $client->forceStandalone();
            }
            $this->clients[] = $client;
            for ($replica = 0; $replica <= $this->replicas; $replica++) {
                $md5num = hexdec(substr(md5($client->getHost() . ':' . $client->getPort() . '-' . $replica), 0, 7));
                $this->ring[$md5num] = count($this->clients) - 1;
            }
        }
        ksort($this->ring, SORT_NUMERIC);
        $this->nodes = array_keys($this->ring);
        $this->dont_hash = array_flip(array(
            'RANDOMKEY', 'DBSIZE', 'PIPELINE', 'EXEC',
            'SELECT', 'MOVE', 'FLUSHDB', 'FLUSHALL',
            'SAVE', 'BGSAVE', 'LASTSAVE', 'SHUTDOWN',
            'INFO', 'MONITOR', 'SLAVEOF'
        ));
        if ($this->masterClient !== null && count($this->clients()) == 0) {
            $this->clients[] = $this->masterClient;
            for ($replica = 0; $replica <= $this->replicas; $replica++) {
                $md5num = hexdec(substr(md5($this->masterClient->getHost() . ':' . $this->masterClient->getHost() . '-' . $replica), 0, 7));
                $this->ring[$md5num] = count($this->clients) - 1;
            }
            $this->nodes = array_keys($this->ring);
        }
    }

    /**
     * @param Credis_Client $masterClient
     * @param bool $writeOnly
     * @return Credis_Cluster
     */
    public function setMasterClient(Credis_Client $masterClient, $writeOnly = false)
    {
        if (!$masterClient instanceof Credis_Client) {
            throw new CredisException('Master client should be an instance of Credis_Client');
        }
        $this->masterClient = $masterClient;
        if (!isset($this->aliases['master'])) {
            $this->aliases['master'] = $masterClient;
        }
        if (!$writeOnly) {
            $this->clients[] = $this->masterClient;
            for ($replica = 0; $replica <= $this->replicas; $replica++) {
                $md5num = hexdec(substr(md5($this->masterClient->getHost() . ':' . $this->masterClient->getHost() . '-' . $replica), 0, 7));
                $this->ring[$md5num] = count($this->clients) - 1;
            }
            $this->nodes = array_keys($this->ring);
        }
        return $this;
    }

    /**
     * Get a client by index or alias.
     *
     * @param string|int $alias
     * @return Credis_Client
     * @throws CredisException
     */
    public function client($alias)
    {
        if (is_int($alias) && isset($this->clients[$alias])) {
            return $this->clients[$alias];
        } elseif (isset($this->aliases[$alias])) {
            return $this->aliases[$alias];
        }
        throw new CredisException("Client $alias does not exist.");
    }

    /**
     * Get an array of all clients
     *
     * @return array|Credis_Client[]
     */
    public function clients()
    {
        return $this->clients;
    }

    /**
     * Execute a command on all clients
     *
     * @return array
     */
    public function all()
    {
        $args = func_get_args();
        $name = array_shift($args);
        $results = array();
        foreach ($this->clients as $client) {
            $results[] = call_user_func_array([$client, $name], $args);
        }
        return $results;
    }

    /**
     * Get the client that the key would hash to.
     *
     * @param string $key
     * @return \Credis_Client
     */
    public function byHash($key)
    {
        return $this->clients[$this->hash($key)];
    }

    /**
     * @param int $index
     * @return void
     */
    public function select($index)
    {
        $this->selectedDb = (int)$index;
    }

    /**
     * Execute a Redis command on the cluster with automatic consistent hashing and read/write splitting
     *
     * @param string $name
     * @param array $args
     * @return mixed
     */
    public function __call($name, $args)
    {
        if ($this->masterClient !== null && !$this->isReadOnlyCommand($name)) {
            $client = $this->masterClient;
        } elseif (count($this->clients()) == 1 || isset($this->dont_hash[strtoupper($name)]) || !isset($args[0])) {
            $client = $this->clients[0];
        } else {
            $hashKey = $args[0];
            if (is_array($hashKey)) {
                $hashKey = join('|', $hashKey);
            }
            $client = $this->byHash($hashKey);
        }
        // Ensure that current client is working on the same database as expected.
        if ($client->getSelectedDb() != $this->selectedDb) {
            $client->select($this->selectedDb);
        }
        return call_user_func_array([$client, $name], $args);
    }

    /**
     * Get client index for a key by searching ring with binary search
     *
     * @param string $key The key to hash
     * @return int The index of the client object associated with the hash of the key
     */
    public function hash($key)
    {
        $needle = hexdec(substr(md5($key), 0, 7));
        $server = $min = 0;
        $max = count($this->nodes) - 1;
        while ($max >= $min) {
            $position = (int)(($min + $max) / 2);
            $server = $this->nodes[$position];
            if ($needle < $server) {
                $max = $position - 1;
            } elseif ($needle > $server) {
                $min = $position + 1;
            } else {
                break;
            }
        }
        return $this->ring[$server];
    }

    public function isReadOnlyCommand($command)
    {
        static $readOnlyCommands = array(
            'DBSIZE' => true,
            'INFO' => true,
            'MONITOR' => true,
            'EXISTS' => true,
            'TYPE' => true,
            'KEYS' => true,
            'SCAN' => true,
            'RANDOMKEY' => true,
            'TTL' => true,
            'GET' => true,
            'MGET' => true,
            'SUBSTR' => true,
            'STRLEN' => true,
            'GETRANGE' => true,
            'GETBIT' => true,
            'LLEN' => true,
            'LRANGE' => true,
            'LINDEX' => true,
            'SCARD' => true,
            'SISMEMBER' => true,
            'SINTER' => true,
            'SUNION' => true,
            'SDIFF' => true,
            'SMEMBERS' => true,
            'SSCAN' => true,
            'SRANDMEMBER' => true,
            'ZRANGE' => true,
            'ZREVRANGE' => true,
            'ZRANGEBYSCORE' => true,
            'ZREVRANGEBYSCORE' => true,
            'ZCARD' => true,
            'ZSCORE' => true,
            'ZCOUNT' => true,
            'ZRANK' => true,
            'ZREVRANK' => true,
            'ZSCAN' => true,
            'HGET' => true,
            'HMGET' => true,
            'HEXISTS' => true,
            'HLEN' => true,
            'HKEYS' => true,
            'HVALS' => true,
            'HGETALL' => true,
            'HSCAN' => true,
            'PING' => true,
            'AUTH' => true,
            'SELECT' => true,
            'ECHO' => true,
            'QUIT' => true,
            'OBJECT' => true,
            'BITCOUNT' => true,
            'TIME' => true,
            'SORT' => true,
        );
        return array_key_exists(strtoupper($command), $readOnlyCommands);
    }
}