Determine dsn string for PDO to connect multiple nodes. If one node is down, removes it ASAP ( in this script it takes max 15 secs )

DetermineDSNForPDO.php

<?php


class DetermineDSNForPDO{



    public $dsn = '';

    public $system_failover = FALSE;

    public $node_failover   = array();



    public function __construct( $type, $nodes, $port ){

        $system_failover= strtoupper( $type ) . "_FAILOVER";

        $dsn_key        = strtoupper( $type ) . "_DSN";

        $dsn_expire_key = strtoupper( $type ) . "_DSN_EXPIRE";

        $dsn        = apc_fetch( $dsn_key );

        $dsn_expire = apc_fetch( $dsn_expire_key );

        $failover   = apc_fetch( $system_failover );

        if( $failover === 1 ){

            $this->system_failover = TRUE;
        }
        else{

            if( $dsn === FALSE ){

                $dsn = $this->determine_dsn( $type, $nodes, $port );

                apc_store( $dsn_key, $dsn );

                apc_store( $dsn_expire_key, 1, 15 );

                $dsn_expire = 1;
            }

            if( $dsn_expire === FALSE ){

                apc_store( $dsn_expire_key, 1, 15 );

                $dsn = $this->determine_dsn( $type, $nodes, $port );

                apc_store( $dsn_key, $dsn );

                if( $this->system_failover === TRUE ){

                    apc_store( $system_failover, 1, 15 );
                }
            }

            $this->dsn = $dsn;
        }
    }



    private function determine_dsn( $type, $nodes, $port ){


        $node_failover = 0;

        $nof_nodes     = count( $nodes );

        $first         = 1;

        $dsn           = $type . ":";

        foreach ( $nodes as $node ){

            $fp = @fsockopen( "tcp://" . $node, $port, $errno, $errstr, 0.05 );

            if ( $fp ) {

                fclose( $fp );

                if( $first == 0 ){

                    $dsn .= ",";
                }

                $dsn .= "host=" . $node . ";port=" . $port;

                $first = 0 ;
            }
            else{

                $node_failover++;

                $this->node_failover[] = $node . ":" . $port;
            }
        }

        if( $node_failover == $nof_nodes ){

            $this->system_failover = TRUE;
        }

        return $dsn;
    }
}

?>