MySQL Connector/J 8.0 Developer Guide

9.2 Configuring Server Failover for Connections Using X DevAPI

When using the X Protocol, Connector/J supports a client-side failover feature for establishing a Session. If multiple hosts are specified in the connection URL, when Connector/J fails to connect to a listed host, it tries to connect to another one. This is a sample X DevAPI URL for configuring client-side failover:


With the client-side failover configured, when there is a failure to establish a connection, Connector/J keeps attempting to connect to a host on the host list. The order in which the hosts are attempted for connection is as follows:

Notice that the server failover feature for X DevAPI only allows for a failover when Connector/J is trying to establish a connection, but not during operations after a connection has already been made.

Connection Pooling Using X DevAPI.  When using connection pooling with X DevAPI, Connector/J keeps track of any host it failed to connect to and, for a short waiting period after the failure, avoids connecting to it during the creation or retrieval of a Session. However, if all other hosts have already been tried, those excluded hosts will be retried without waiting. Once all hosts have been tried and no connections can be established, Connector/J throws a com.mysql.cj.exceptions.CJCommunicationsException and returns the message Unable to connect to any of the target hosts.

Configuring Server Failover Using X DevAPI with DNS SRV

See Section 6.13, “Support for DNS SRV Records” for details.