Advanced Configuration

Service Load-Balancing

Domain Load-Balancing Algorithm

ejabberd includes an algorithm to load balance the components that are plugged on an ejabberd cluster. It means that you can plug one or several instances of the same component on each ejabberd cluster and that the traffic will be automatically distributed.

The default distribution algorithm attempts to deliver to a local instance of a component. If several local instances are available, one instance is chosen at random. If no instance is available locally, one instance is randomly chosen among the remote component instances.

If you need a different behaviour, you can change the load balancing behaviour with the option domain_balancing. The syntax of the option is the following:

domain_balancing: BalancingCriteria: Several balancing criterias are available:

  • destination: the full JID of the packet to attribute is used.

  • source: the full JID of the packet from attribute is used.

  • bare_destination: the bare JID (without resource) of the packet to attribute is used.

  • bare_source: the bare JID (without resource) of the packet from attribute is used.

If the value corresponding to the criteria is the same, the same component instance in the cluster will be used.

Load-Balancing Buckets

When there is a risk of failure for a given component, domain balancing can cause service trouble. If one component is failing the service will not work correctly unless the sessions are rebalanced.

In this case, it is best to limit the problem to the sessions handled by the failing component. This is what the domain_balancing_component_number option does, making the load balancing algorithm not dynamic, but sticky on a fix number of component instances.

The syntax is:

domain_balancing_component_number: Number