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<?php
/**
* Service discovery using DNS SRV records
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
/**
* @since 1.29
*/
class DnsSrvDiscoverer {
/**
* @var string
*/
private $domain;
/**
* @param string $domain
*/
public function __construct( $domain ) {
$this->domain = $domain;
}
/**
* Fetch the servers with a DNS SRV request
*
* @return array
*/
public function getServers() {
$result = [];
foreach ( $this->getDnsRecords() as $record ) {
$result[] = [
'target' => $record['target'],
'port' => $record['port'],
'pri' => $record['pri'],
'weight' => $record['weight'],
];
}
return $result;
}
/**
* Pick a server according to the priority fields.
* Note that weight is currently ignored.
*
* @param array $servers from getServers
* @return array|bool
*/
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];
}
}
/**
* @param array $server
* @param array $servers
* @return array[]
*/
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 );
}
/**
* @return array[]
*/
protected function getDnsRecords() {
return dns_get_record( $this->domain, DNS_SRV );
}
}
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