High Availability

Enterprise applications often require the ability to run continuously for extended periods of time with little or no user-facing downtime.

Replication

MariaDB Enterprise Server and MariaDB Community Server support several different replication options that enable high availability:

Replication	Description
MariaDB Replication	Asynchronous and semi-synchronous replication that relies on binary logs.
Galera Cluster	Certification-based replication that relies on the Galera 3 or Galera 4 plugin, depending on the version of MariaDB.
Multi-Node Enterprise ColumnStore	Enterprise ColumnStore supports highly available multi-node deployments.
Xpand	MariaDB Xpand is highly available by design.

Replication	Supported by MariaDB Enterprise Server	Supported by MariaDB Community Server
MariaDB Replication	Yes	Yes
Galera Cluster	Yes	Yes
Multi-Node Enterprise ColumnStore	Yes	No
Xpand	Yes	No

MaxScale's automatic failover capabilities depend on the specific replication solution that is used.:

Replication	Description
MariaDB Replication	MaxScale's MariaDB Monitor (mariadbmon) detects primary server failure and promotes the most up-to-date replica based on Global Transaction ID (GTID), waits for that replica to execute any transactions in its relay log, and begins routing queries to it.
Galera Cluster	MaxScale's Galera Monitor (galeramon) is used to minimize application impact upon server failure. Additionally, MaxScale may be used to assign primary and replica roles to database instances within a cluster to support read/write traffic splitting and to minimize the risk of certification failures.
Multi-Node Enterprise ColumnStore	MaxScale's MariaDB Monitor (mariadbmon) determines which node is the primary server, and automatically performs failover upon primary server failure.

MaxScale's Read/Write Split Router (readwritesplit) includes several configurable features to minimize the impact of failover on client connections:

Feature	Description
Automatic Reconnection	Replaces back-end server connections to a failed server with connections to a different server, rather than closing the connections.
Transaction Replay	Ensures the execution of prior transactions before additional queries are routed to different Servers, instead of closing the connection and requiring the application to roll the transaction back and retry.
Connection Maintenance and Restore	Ensures all servers handling traffic for a connection have the same session system variables, user-defined variables, etc.
Read Retry	Allows MaxScale to route incomplete queries to a different replica rather than returning an error or closing the client connection.
Delayed Retry	Allows MaxScale to delay and retry write queries received after a primary fails and before automatic failover completes, rather than returning an error or closing the client connection

MariaDB Replication	Deploy a Primary Server with MariaDB Enterprise Server Deploy a Replica Server with MariaDB Enterprise Server Deploy a Primary Server with MariaDB Community Server Deploy a Replica Server with MariaDB Community Server
Galera Cluster	Deploy an Enterprise Cluster Node with MariaDB Enterprise Server Deploy a Galera Cluster Node with MariaDB Community Server
Multi-Node Enterprise ColumnStore	Deploy Multi-Node Enterprise ColumnStore

Choose a front-end MariaDB MaxScale deployment: