private boolean mayOverrideWithGetOnlyRoute(Message msg) {
        // Only allow implicitly overriding the default Get route if the message is attempted sent
        // with the default route originally. Otherwise it's reasonable to assume that the caller
        // has some explicit idea of why the regular route is set to the value it is.
        return ((msg.getType() == DocumentProtocol.MESSAGE_GETDOCUMENT)
                && ("default".equals(route) || "route:default".equals(route)));
    }
Creates a new async session running on message bus logic with a specified reply handler.

@param asyncParams common asyncsession parameters, not used
@param bus         the message bus on which to run
@param mbusParams  parameters concerning message bus configuration
@param handler     the external reply handler
documentapi/src/main/java/com/yahoo/documentapi/messagebus/MessageBusAsyncSession.java