This topic is generated automatically from the corresponding README in the Magento codebase. If you want to contribute, refer to Magento Code Contributions.
Magento\ResourceConnections module adds a mechanism to segregate database connections between master and slave database servers based on the request type.
For each master database connection (except the indexer connection) that are configured in db/connection section of app/etc/env.php you can add one slave connection that can be configured in db/slave_connection. Configuration format is the same as db/connection. Slave connection name must be the same as associated master connection name. To enable slave connections for specific resources create a slave connection configuration by adding slave_connection node as below:
<?php return array ( //... 'db' => array ( 'connection' => array ( 'default' => array ( 'host' => 'default-master-host', 'dbname' => 'magento', 'username' => 'magento', 'password' => 'magento', 'active' => '1', ), ), 'slave_connection' => array ( 'default' => array ( 'host' => 'default-slave-host', 'dbname' => 'magento', 'username' => 'read_only', 'password' => 'password', 'active' => '1', ), ), 'table_prefix' => '', ), //.......
To add slave connection for resources other than ‘default’ repeat the step and add to db/slave_connection new element with same name and slave configuration for specified resource. Config structure retains backward compatibility if module is turned off.
WARNING: ‘indexer’ connection is not designed to have slave configuration.