--- /dev/null
+<?php
+
+namespace Wikimedia\Rdbms;
+
+use InvalidArgumentException;
+
+/**
+ * Database connection manager.
+ *
+ * This manages access to master and replica databases.
+ *
+ * @since 1.29
+ *
+ * @license GPL-2.0+
+ * @author Addshore
+ */
+class ConnectionManager {
+
+ /**
+ * @var LoadBalancer
+ */
+ private $loadBalancer;
+
+ /**
+ * The symbolic name of the target database, or false for the local wiki's database.
+ *
+ * @var string|false
+ */
+ private $domain;
+
+ /**
+ * @var string[]
+ */
+ private $groups = [];
+
+ /**
+ * @param LoadBalancer $loadBalancer
+ * @param string|bool $domain Optional logical DB name, defaults to current wiki.
+ * This follows the convention for database names used by $loadBalancer.
+ * @param string[] $groups see LoadBalancer::getConnection
+ *
+ * @throws InvalidArgumentException
+ */
+ public function __construct( LoadBalancer $loadBalancer, $domain = false, array $groups = [] ) {
+ if ( !is_string( $domain ) && $domain !== false ) {
+ throw new InvalidArgumentException( '$dbName must be a string, or false.' );
+ }
+
+ $this->loadBalancer = $loadBalancer;
+ $this->domain = $domain;
+ $this->groups = $groups;
+ }
+
+ /**
+ * @param int $i
+ * @param string[]|null $groups
+ *
+ * @return Database
+ */
+ private function getConnection( $i, array $groups = null ) {
+ $groups = $groups === null ? $this->groups : $groups;
+ return $this->loadBalancer->getConnection( $i, $groups, $this->domain );
+ }
+
+ /**
+ * @param int $i
+ * @param string[]|null $groups
+ *
+ * @return DBConnRef
+ */
+ private function getConnectionRef( $i, array $groups = null ) {
+ $groups = $groups === null ? $this->groups : $groups;
+ return $this->loadBalancer->getConnectionRef( $i, $groups, $this->domain );
+ }
+
+ /**
+ * Returns a connection to the master DB, for updating. The connection should later be released
+ * by calling releaseConnection().
+ *
+ * @since 1.29
+ *
+ * @return Database
+ */
+ public function getWriteConnection() {
+ return $this->getConnection( DB_MASTER );
+ }
+
+ /**
+ * Returns a database connection for reading. The connection should later be released by
+ * calling releaseConnection().
+ *
+ * @since 1.29
+ *
+ * @param string[]|null $groups
+ *
+ * @return Database
+ */
+ public function getReadConnection( array $groups = null ) {
+ $groups = $groups === null ? $this->groups : $groups;
+ return $this->getConnection( DB_REPLICA, $groups );
+ }
+
+ /**
+ * @since 1.29
+ *
+ * @param IDatabase $db
+ */
+ public function releaseConnection( IDatabase $db ) {
+ $this->loadBalancer->reuseConnection( $db );
+ }
+
+ /**
+ * Returns a connection ref to the master DB, for updating.
+ *
+ * @since 1.29
+ *
+ * @return DBConnRef
+ */
+ public function getWriteConnectionRef() {
+ return $this->getConnectionRef( DB_MASTER );
+ }
+
+ /**
+ * Returns a database connection ref for reading.
+ *
+ * @since 1.29
+ *
+ * @param string[]|null $groups
+ *
+ * @return DBConnRef
+ */
+ public function getReadConnectionRef( array $groups = null ) {
+ $groups = $groups === null ? $this->groups : $groups;
+ return $this->getConnectionRef( DB_REPLICA, $groups );
+ }
+
+}