protected void setNewConfig(JRTClientConfigRequest jrtReq) {
        try {
            T configInstance = toConfigInstance(jrtReq);
            setConfig(jrtReq.getNewGeneration(), jrtReq.responseIsApplyOnRestart(), configInstance, jrtReq.getNewChecksums());
        } catch (IllegalArgumentException e) {
            throw new IllegalArgumentException("Bad config in response", e);
        }
    }
Polls the callback queue for new config

@param timeoutMillis timeout when polling (returns after at most this time)
config/src/main/java/com/yahoo/config/subscription/impl/JRTConfigSubscription.java