includes/libs/DnsSrvDiscoverer.php

   1 <?php
   2 /**
   3  * Service discovery using DNS SRV records
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  */
  22
  23 /**
  24  * @since 1.29
  25  */
  26 class DnsSrvDiscoverer {
  27         /**
  28          * @var string
  29          */
  30         private $domain;
  31
  32         /**
  33          * @param string $domain
  34          */
  35         public function __construct( $domain ) {
  36                 $this->domain = $domain;
  37         }
  38
  39         /**
  40          * Fetch the servers with a DNS SRV request
  41          *
  42          * @return array
  43          */
  44         public function getServers() {
  45                 $result = [];
  46                 foreach ( $this->getDnsRecords() as $record ) {
  47                         $result[] = [
  48                                 'target' => $record['target'],
  49                                 'port' => $record['port'],
  50                                 'pri' => $record['pri'],
  51                                 'weight' => $record['weight'],
  52                         ];
  53                 }
  54
  55                 return $result;
  56         }
  57
  58         /**
  59          * Pick a server according to the priority fields.
  60          * Note that weight is currently ignored.
  61          *
  62          * @param array $servers from getServers
  63          * @return array|bool
  64          */
  65         public function pickServer( array $servers ) {
  66                 if ( !$servers ) {
  67                         return false;
  68                 }
  69
  70                 $srvsByPrio = [];
  71                 foreach ( $servers as $server ) {
  72                         $srvsByPrio[$server['pri']][] = $server;
  73                 }
  74
  75                 $min = min( array_keys( $srvsByPrio ) );
  76                 if ( count( $srvsByPrio[$min] ) == 1 ) {
  77                         return $srvsByPrio[$min][0];
  78                 } else {
  79                         // Choose randomly
  80                         $rand = mt_rand( 0, count( $srvsByPrio[$min] ) - 1 );
  81
  82                         return $srvsByPrio[$min][$rand];
  83                 }
  84         }
  85
  86         /**
  87          * @param array $server
  88          * @param array $servers
  89          * @return array[]
  90          */
  91         public function removeServer( $server, array $servers ) {
  92                 foreach ( $servers as $i => $srv ) {
  93                         if ( $srv['target'] === $server['target'] && $srv['port'] === $server['port'] ) {
  94                                 unset( $servers[$i] );
  95                                 break;
  96                         }
  97                 }
  98
  99                 return array_values( $servers );
 100         }
 101
 102         /**
 103          * @return array[]
 104          */
 105         protected function getDnsRecords() {
 106                 return dns_get_record( $this->domain, DNS_SRV );
 107         }
 108 }