@Override
    public void select(RoutingContext ctx) {
        if (error != null) {
            ctx.setError(DocumentProtocol.ERROR_POLICY_FAILURE, error);
        } else if (mirror.ready()) {
            Hop hop = getRecipient();
            if (hop != null) {
                Route route = new Route(ctx.getRoute());
                route.setHop(0, hop);
                ctx.addChild(route);
            } else {
                ctx.setError(ErrorCode.NO_ADDRESS_FOR_SERVICE,
                             "Could not resolve any recipients from '" + pattern + "'.");
            }
        } else {
            ctx.setError(ErrorCode.APP_TRANSIENT_ERROR, "Extern slobrok not ready.");
        }
    }
Updates the list of matching recipients by querying the extern slobrok.
documentapi/src/main/java/com/yahoo/documentapi/messagebus/protocol/ExternPolicy.java