com.mysql.cj.jdbc.ha

Interface BalanceStrategy

public interface BalanceStrategy

Implement this interface to provide a new load balancing strategy for URLs of the form "jdbc:mysql:loadbalance://..", and provide the implementation class name as the configuration parameter "loadBalanceStrategy". The driver will not pass in a Connection instance when calling init(), but it will pass in the Properties, otherwise it acts like a normal Extension. One instance of a strategy *per* JDBC connection instance will be created. If you need singleton-like behavior, you're on your own to provide it.

Method Summary

Modifier and Type	Method and Description
JdbcConnection	pickConnection(InvocationHandler proxy, List<String> configuredHosts, Map<String,JdbcConnection> liveConnections, long[] responseTimes, int numRetries) Called by the driver to pick a new connection to route requests over.

Method Detail

pickConnection

JdbcConnection pickConnection(InvocationHandler proxy,
                              List<String> configuredHosts,
                              Map<String,JdbcConnection> liveConnections,
                              long[] responseTimes,
                              int numRetries)
                       throws SQLException

Called by the driver to pick a new connection to route requests over. See LoadBalancedConnectionProxy.createConnectionForHost(String)

Parameters:

proxy - the InvocationHandler that deals with actual method calls to the JDBC connection, and serves as a factory for new connections for this strategy via the createConnectionForHost() method. This proxy takes care of maintaining the response time list, map of host/ports to live connections, and taking connections out of the live connections map if they receive a network-related error while they are in use by the application.

configuredHosts - the list of hosts/ports (in "host:port" form) as passed in by the user.

liveConnections - a map of host/ports to "live" connections to them.

responseTimes - the list of response times for a transaction for each host in the configured hosts list.

numRetries - the number of times the driver expects this strategy to re-try connection attempts if creating a new connection fails.

Returns:

the physical JDBC connection for the application to use, based upon the strategy employed.

Throws:

SQLException - if a new connection can not be found or created by this strategy.