Reconnecting to the Primary Server with MaxScale's Read/Write Split Router

Overview

The Read/Write Split Router (readwritesplit) routes write queries to the primary server and load balances read-only queries between one or more replica servers. If the primary server fails, then the router can automatically reconnect existing client connections to the new primary server.

Configuring Automatic Primary Server Re-connection

  1. Configure automatic primary server re-connection by configuring several parameters for the Read/Write Split Router in maxscale.cnf.

    Parameter

    Description

    master_reconnection

    • When this parameter is enabled, if the primary server fails and if master_failure_mode is not set to fail_instantly, then existing client connections will be automatically reconnected to the new primary server.

    • This parameter is disabled by default.

    master_failure_mode

    • This parameter defines how client connections are handled when the primary server fails.

    • This parameter must be set to either fail_on_write or error_on_write to allow automatic primary server reconnection.

    • When this parameter is set to fail_on_write, the client connection is closed if a write query is received when no primary is available.

    • When this parameter is set to error_on_write, if no primary server is available and a write query is received, an error is returned stating that the connection is in read-only mode.

    For example:

    [split-router]
type                     = service
router                   = readwritesplit
...
master_reconnection            = true
master_failure_mode            = fail_on_write

  2. Restart the MaxScale instance.

    $ sudo systemctl restart maxscale