django-galera 0.9

Django database backend for MariaDB Galera Cluster

A Django application providing a database backend for MariaDB Galera Cluster.

Features

• Loadbalancing: Randomly choose a secondary node for readonly queries to balance load over multiple database servers

• Read/Write Splitting: Route all writes to a single primary node, which will greatly reduce deadlocks

• Optimistic transactions on secondary nodes: Switching to the primary node only once a write happens

• Automatic and transparent failover: On connection failures the backend will reconnect to a different node. After that a transaction replay will ensure data consistency, making a failure of both primary and secondary nodes transparent to the application

Setup

DATABASES = {
    'default': {
        'ATOMIC_REQUESTS': True,
        'ENGINE': 'galera.backends.readwritesplit',
        # if HOST is omitted, a random node will be used for secondary (readonly) access
        # HOST can still be set to prioritize a node (useful if app and db are running on the same machine)
        # 'HOST': 'localhost',                      # prefer a local node for faster access times
        # 'HOST': '/var/run/mysqld/mysqld.sock',    # also works with sockets
        'PORT': 3306,
        'NAME': 'db_name',
        'USER': 'db_username',
        'PASSWORD': 'db_password',
        'OPTIONS': {
            'failover_enable': True,  # enable transparent failover with transaction replay
            'failover_history_limit': 1000,  # disable replay for connections reaching this limit (saves memory)
            'wsrep_sync_after_write': True,  # explicitly wait until writes from primary have been applied before reading from secondary
            'wsrep_sync_use_gtid': False,  # use WSREP_SYNC_UPTO_GTID for syncing secondary node (currently not recommended because of MariaDB issue MDEV-26359)
            # options are also attributes of django.db.connection and can be changed on the fly for the current connection
        },
        'NODES': {
            'db1': {'HOST': '10.0.1.2'},  # first node becomes primary and is preferred for read/write transactions
            'db2': {'HOST': '10.0.1.3'},  # following nodes are secondary nodes, used for readonly transactions
            'db3': {'HOST': '10.0.1.4'},
            # 'db4': {'HOST': '10.0.1.4', 'PORT': 3307},    # node settings inherit but can be overwritten
        }
    }
}

MIDDLEWARE = [
    # Optional: the middleware repeats a request if a deadlock occurs
    'galera.middleware.GaleraMiddleware'
]