public RoutingPolicy getRoutingPolicy(String protocolName, String policyName, String policyParam) {
        return protocolRepository.getRoutingPolicy(protocolName, policyName, policyParam);
    }
<p>Returns a routing policy that corresponds to the argument protocol
name, policy name and policy parameter. This will cache reuse all
policies as soon as they are first requested.</p>

@param protocolName The name of the protocol to invoke {@link Protocol#createPolicy(String,String)} on.
@param policyName   The name of the routing policy to retrieve.
@param policyParam  The parameter for the routing policy to retrieve.
@return A corresponding routing policy, or null.
messagebus/src/main/java/com/yahoo/messagebus/MessageBus.java