Rolling Upgrades
Users with highly available clusters under heavy transaction loads may want to upgrade to a newer version of MarkLogic in a seamless manner. A rolling upgrade, where hosts in a cluster are upgraded one by one, is one approach to addressing this need. Rolling upgrades are used to upgrade a large cluster with many hosts to a newer version of MarkLogic Server without incurring any downtime in availability or interruption of transactions. A rolling upgrade may also be used to apply patches to multiple hosts.
The goal in performing a rolling upgrade is to have zero downtime of your server availability or transactional data. This is most useful for large high availability (HA) clusters that have a large number of ongoing transactions. A rolling upgrade can be performed on both a primary cluster and a disaster recovery (DR) cluster.
Note
Do not change your application to take advantage of any new features until all the nodes in your cluster have been upgraded. In addition, you should avoid making any configuration changes to your cluster during a rolling upgrade.
This section describes rolling upgrades.