getReplicaServer.php

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<?php
require_once __DIR__ . '/Maintenance.php';
 
use MediaWiki\MediaWikiServices;
 
class GetReplicaServer extends Maintenance {
    public function __construct() {
        parent::__construct();
        $this->addOption( "group", "Query group to check specifically" );
        $this->addOption( 'cluster', 'Use an external cluster by name', false, true );
        $this->addDescription( 'Report the hostname of a replica DB server' );
    }
 
    public function execute() {
        $lbf = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
        if ( $this->hasOption( 'cluster' ) ) {
            try {
                $lb = $lbf->getExternalLB( $this->getOption( 'cluster' ) );
            } catch ( InvalidArgumentException $e ) {
                $this->fatalError( 'Error: ' . $e->getMessage() );
            }
        } else {
            $lb = $lbf->getMainLB();
        }
 
        $group = $this->getOption( 'group', false );
        $index = $lb->getReaderIndex( $group );
        if ( $index === false && $group ) {
            // retry without the group; it may not exist
            $index = $lb->getReaderIndex( false );
        }
        if ( $index === false ) {
            $this->fatalError( 'Error: unable to get reader index' );
        }
 
        $this->output( $lb->getServerName( $index ) . "\n" );
    }
}
 
$maintClass = GetReplicaServer::class;
require_once RUN_MAINTENANCE_IF_MAIN;