public static void validateRequestKey(ConfigKey<?> requestKey, RequestHandler requestHandler, ApplicationId appId) {
        Set<ConfigKey<?>> allConfigsProduced = requestHandler.allConfigsProduced(appId, Optional.empty());
        if (allConfigsProduced.isEmpty()) {
            // This will happen if the configserver is starting up, but has not built a config model
            throwModelNotReady();
        }
        if (configNameNotFound(requestKey, allConfigsProduced)) {
            throw new NotFoundException("No such config: " + requestKey.getNamespace() + "." + requestKey.getName());
        }
        if (configIdNotFound(requestHandler, requestKey, appId)) {
            throw new NotFoundException("No such config id: " + requestKey.getConfigId());
        }
    }
Throws an exception if bad config or config id

@param requestKey     a {@link com.yahoo.vespa.config.ConfigKey}
@param requestHandler a {@link RequestHandler}
@param appId appId
configserver/src/main/java/com/yahoo/vespa/config/server/http/HttpConfigRequest.java