ServerInfo.php
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ServerInfo.php
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	<?php

	namespace Wikimedia\Rdbms;

	use InvalidArgumentException;
	use UnexpectedValueException;

	/**
	* Container for accessing information about the database servers in a database cluster
	*
	* @internal
	* @ingroup Database
	*/
	class ServerInfo {
	/**
	* Default 'maxLag' when unspecified
	* @internal Only for use within LoadBalancer/LoadMonitor
	*/
	public const MAX_LAG_DEFAULT = 6;

	public const WRITER_INDEX = 0;

	/** @var array[] Map of (server index => server config array) */
	private $servers;

	public function addServer( int $i, array $server ) {
	$this->servers[$i] = $server;
	}

	public function getServerMaxLag( int $i ): int {
	return $this->servers[$i]['max lag'] ?? self::MAX_LAG_DEFAULT;
	}

	public function getServerDriver( int $i ): ?string {
	return $this->servers[$i]['driver'] ?? null;
	}

	public function getServerType( int $i ): string {
	return $this->servers[$i]['type'] ?? 'unknown';
	}

	public function getServerName( int $i ): string {
	return $this->servers[$i]['serverName'] ?? 'localhost';
	}

	public function getServerInfo( int $i ): array\|false {
	return $this->servers[$i] ?? false;
	}

	public function getServerCount(): int {
	return count( $this->servers );
	}

	public function hasServerIndex( int $i ): bool {
	return isset( $this->servers[$i] );
	}

	public function getLagTimes(): array {
	$knownLagTimes = []; // map of (server index => 0 seconds)
	$indexesWithLag = [];
	foreach ( $this->servers as $i => $server ) {
	if ( empty( $server['is static'] ) ) {
	$indexesWithLag[] = $i; // DB server might have replication lag
	} else {
	$knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
	}
	}

	return [ $indexesWithLag, $knownLagTimes ];
	}

	/**
	* @param int $i Server index
	* @param string\|null $field Server index field [optional]
	* @return mixed
	* @throws InvalidArgumentException
	*/
	public function getServerInfoStrict( $i, $field = null ) {
	if ( !isset( $this->servers[$i] ) \|\| !is_array( $this->servers[$i] ) ) {
	throw new InvalidArgumentException( "No server with index '$i'" );
	}

	if ( $field !== null ) {
	if ( !array_key_exists( $field, $this->servers[$i] ) ) {
	throw new InvalidArgumentException( "No field '$field' in server index '$i'" );
	}

	return $this->servers[$i][$field];
	}

	return $this->servers[$i];
	}

	/**
	* @return int[] List of replica server indexes
	*/
	public function getStreamingReplicaIndexes() {
	$indexes = [];
	foreach ( $this->servers as $i => $server ) {
	if ( $i !== self::WRITER_INDEX && empty( $server['is static'] ) ) {
	$indexes[] = $i;
	}
	}

	return $indexes;
	}

	public function hasStreamingReplicaServers(): bool {
	return (bool)$this->getStreamingReplicaIndexes();
	}

	public function reconfigureServers( array $paramServers ): array {
	$newIndexBySrvName = [];
	$this->normalizeServerMaps( $paramServers, $newIndexBySrvName );

	// Map of (existing server index => corresponding index in new config or null)
	$newIndexByServerIndex = [];
	// Remove servers that no longer exist in the new config and preserve those that
	// still exist, even if they switched replication roles (e.g. primary/secondary).
	// Note that if the primary server is depooled and a replica server is promoted
	// to primary, then DB_PRIMARY handles will fail with server index errors. Note
	// that if the primary server swaps roles with a replica server, then write queries
	// to DB_PRIMARY handles will fail with read-only errors.
	foreach ( $this->servers as $i => $server ) {
	$srvName = $this->getServerName( $i );
	// Since pooling or depooling of servers causes the remaining servers to be
	// assigned different indexes, find the corresponding index by server name.
	// Also, note that the primary can be reconfigured as a replica (moved from
	// the writer index) and vice versa (moved to the writer index).
	$newIndex = $newIndexByServerIndex[$i] = $newIndexBySrvName[$srvName] ?? null;
	if ( $newIndex === null ) {
	unset( $this->servers[$i] );
	}
	}

	return $newIndexByServerIndex;
	}

	public function normalizeServerMaps( array $servers, ?array &$indexBySrvName = null ): array {
	if ( !$servers ) {
	throw new InvalidArgumentException( 'Missing or empty "servers" parameter' );
	}

	$listKey = -1;
	$indexBySrvName = [];
	foreach ( $servers as $i => $server ) {
	if ( ++$listKey !== $i ) {
	throw new UnexpectedValueException( 'List expected for "servers" parameter' );
	}
	$srvName = $server['serverName'] ?? $server['host'] ?? '';
	$srvName = ( $srvName !== '' ) ? $srvName : 'localhost';
	if ( isset( $indexBySrvName[$srvName] ) ) {
	// Duplicate server names confuse caching, logging, and reconfigure()
	throw new UnexpectedValueException( 'Duplicate server name "' . $srvName . '"' );
	}
	$indexBySrvName[$srvName] = $i;
	$servers[$i]['serverName'] = $srvName;
	$servers[$i]['groupLoads'] ??= [];
	}
	return $servers;
	}

	/**
	* @return string Name of the primary DB server of the relevant DB cluster (e.g. "db1052")
	*/
	public function getPrimaryServerName() {
	return $this->getServerName( self::WRITER_INDEX );
	}

	public function hasReplicaServers(): bool {
	return ( $this->getServerCount() > 1 );
	}
	}

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