For services that use Zookeeper based HA there is no documentation about how the failover scenario works.
The failover code is a simple round-robin. All URLs are tried once on failover. When the list is exhausted the entire list of URLs is re-fetched from Zookeeper and the new list is tried again the same way (if the configured number of failover attempts has not been reached).
Upon failure, the url is marked failed and next is tried and used until it fails.
This needs to be explicitly documented for clear understanding of HA workings.