DnsSrvDiscoverer.php

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<?php
class DnsSrvDiscoverer {
    private $domain;
 
    public function __construct( $domain ) {
        $this->domain = $domain;
    }
 
    public function getServers() {
        $result = [];
        foreach ( $this->getDnsRecords() as $record ) {
            $result[] = [
                'target' => $record['target'],
                'port' => $record['port'],
                'pri' => $record['pri'],
                'weight' => $record['weight'],
            ];
        }
 
        return $result;
    }
 
    public function pickServer( array $servers ) {
        if ( !$servers ) {
            return false;
        }
 
        $srvsByPrio = [];
        foreach ( $servers as $server ) {
            $srvsByPrio[$server['pri']][] = $server;
        }
 
        $min = min( array_keys( $srvsByPrio ) );
        if ( count( $srvsByPrio[$min] ) == 1 ) {
            return $srvsByPrio[$min][0];
        } else {
            // Choose randomly
            $rand = mt_rand( 0, count( $srvsByPrio[$min] ) - 1 );
 
            return $srvsByPrio[$min][$rand];
        }
    }
 
    public function removeServer( $server, array $servers ) {
        foreach ( $servers as $i => $srv ) {
            if ( $srv['target'] === $server['target'] && $srv['port'] === $server['port'] ) {
                unset( $servers[$i] );
                break;
            }
        }
 
        return array_values( $servers );
    }
 
    protected function getDnsRecords() {
        return dns_get_record( $this->domain, DNS_SRV );
    }
}