A Doctrine (Symfony) master-replica database configuration

.env

# SET YOUR ENVS :)

# Master Database Environment Variables
DATABASE_DRIVER=pdo_mysql
DATABASE_HOST=mysql-master-host
DATABASE_PORT=3306
DATABASE_NAME=app
DATABASE_USER=root
DATABASE_PASSWORD=root
DATABASE_SERVER_VERSION=8
DATABASE_CHARSET=utf8mb4

# Database replica 1 configuration
DATABASE_REPLICA1_HOST=mysql-replica1-host
DATABASE_REPLICA1_DATABASE_NAME=app
DATABASE_REPLICA1_PORT=3306
DATABASE_REPLICA1_USER=root
DATABASE_REPLICA1_PASSWORD=root
DATABASE_REPLICA1_CHARSET=utf8mb4

# Database replica 2 configuration
DATABASE_REPLICA2_HOST=mysql-replica2-host
DATABASE_REPLICA2_DATABASE_NAME=app
DATABASE_REPLICA2_PORT=3306
DATABASE_REPLICA2_USER=root
DATABASE_REPLICA2_PASSWORD=root
DATABASE_REPLICA2_CHARSET=utf8mb4

README.md

Doctrine (Symfony) Master-Replica(s) configuration

I was struggling to set this up because most documentation I found refers to the replicas as slaves (which is a terminology still in use by MySQL, for example). The newer Doctrine versions use the term replicas to refer to slave servers.

You're welcome :)

doctrine.yaml

doctrine:
    dbal:
        # IMPORTANT: You MUST configure your server version,
        # either here or in the DATABASE_URL env var (see .env file)
        #server_version: '15'

        default_connection: default
        connections:
            default:
                driver:         "%env(DATABASE_DRIVER)%"
                host:           "%env(DATABASE_HOST)%"
                port:           "%env(DATABASE_PORT)%"
                dbname:         "%env(DATABASE_NAME)%"
                user:           "%env(DATABASE_USER)%"
                password:       "%env(DATABASE_PASSWORD)%"
                server_version: "%env(DATABASE_SERVER_VERSION)%"
                charset:        "%env(DATABASE_CHARSET)%"


                replicas:
                    replica1:
                        dbname:               "%env(DATABASE_REPLICA1_DATABASE_NAME)%"
                        host:                 "%env(DATABASE_REPLICA1_HOST)%"
                        port:                 "%env(DATABASE_REPLICA1_PORT)%"
                        user:                 "%env(DATABASE_REPLICA1_USER)%"
                        password:             "%env(DATABASE_REPLICA1_PASSWORD)%"
                        charset:              "%env(DATABASE_REPLICA1_CHARSET)%"
                    replica2:
                        dbname:               "%env(DATABASE_REPLICA2_DATABASE_NAME)%"
                        host:                 "%env(DATABASE_REPLICA2_HOST)%"
                        port:                 "%env(DATABASE_REPLICA2_PORT)%"
                        user:                 "%env(DATABASE_REPLICA2_USER)%"
                        password:             "%env(DATABASE_REPLICA2_PASSWORD)%"
                        charset:              "%env(DATABASE_REPLICA2_CHARSET)%"