Load balancing

Four load balancing strategies are supported to
distribute statements over the configured MySQL slave servers:

random

Chooses a random server whenever a statement is
executed.

random once (default)

Chooses a random server after the first statement
is executed, and uses the decision for the rest of the PHP
request.

It is the default, and the lowest impact on the
connection state.

round robin

Iterates over the list of configured servers.

user-defined via callback

Is used to implement any other strategy.

The load balancing policy is configured in the
plugins configuration file using the random, roundrobin, and user filters.

Servers can be prioritized assigning a weight. A
server that has been given a weight of two will get twice as many
requests as a server that has been given the default weight of one.
Prioritization can be handy in heterogenous environments. For
example, you may want to assign more requests to a powerful machine
than to a less powerful. Or, you may have configured servers that
are close or far from the client, thus expose different
latencies.