If you are one of Jive's hosted customers, you have likely heard our Jive support agents use the term "rolling restart" at one time or another.
From a very high level, a rolling restart takes advantage of the Jive application's clustering architecture to restart the individual servers with very minimal interruption to end-users. As opposed to a full restart where the site is unavailable while the servers are starting up, users will still be able to use the service during a rolling restart.
This article covers what rolling restart means, how it will impact your nodes and end-users, and when it's applicable. Usually, you will need to perform a rolling restart after renewing your license or installing an add-on plugin.
What is a Rolling Restart?
From a technical perspective, what we're doing is shutting down each machine individually and relying on the load balancer to redirect traffic away from the downed node. This action has a few noticeable effects on users:
- Users who have not opted for the site to "Remember Me" will need to log in again. This behavior occurs because users' sessions are tied to a particular node, so when they are directed to another node they will need to re-authenticate their session.
- Users who try to access the site may experience a temporary "site down" error before the load balancer begins redirecting traffic.
- Per-node, in-memory state, such as auto-saved RTE posts will be lost.
Possible Uses for Rolling Restarts
For the most part, a rolling restart accomplishes exactly the same goals as a full restart, except that it does not interrupt any end-user services. Each of the nodes will be brought down in turn, which yields a net effect of a full restart for the entire cluster.
There are some limitations to what can be done with a rolling restart and what requires a full restart. For example, while many plugins can be installed via a rolling restart, those that need to install their own database schema cannot. Further, because rolling restarts require manual control, they can only be scheduled during normal business hours. A full restart, on the other hand, is fully automated and can, therefore, be scheduled for any time.
When doing an installation update using the cloud tool, there is a new Rolling Restart checkbox when updating a theme, it is checked by default. The user can select if they want to do a rolling restart. The next confirmation page confirms if a rolling restart has been selected, and the final upload page adds a note saying that a rolling restart will be done.