Could not fetch config from bucket and RuntimeExceptions

These errors have been seen in the environment, I was wondering what causes these kind of errors?

2015-12-09 07:32:11,562 DEBUG [cb-core-3-2] com.couchbase.client.core.config.refresher.CarrierRefresher - Could not fetch config from bucket “<bucket_name>” against “<ip_address>”.
com.couchbase.client.core.RequestCancelledException: Could not dispatch request, cancelling instead of retrying.
at com.couchbase.client.core.retry.RetryHelper.retryOrCancel(RetryHelper.java:51)