Clustering
Clustering is an optional feature that some customers may elect to utilize.
Reasons for using clustered environments
High Availability (if a node leaves the cluster, the application can still be used)
General Performance Increase, for instances with a large number of active users*
Geo-localized Performance Increase (users can be redirected to geographically closer servers and thus see faster response times)
* When compared to the same number of users on a single non-clustered instance
** Only while using Redis
Configuring a cluster
[Deprecation Notice] Configuring a cluster without Redis
Viewing your Cluster Status
You can view your cluster status from every node by navigating to Administration > Support > System Information > Cluster
The node list will contain a host name, IP address, a randomly generated node ID, and the information if the respective node is a cluster lead node and/or a local node. The terms lead and local node are explained below
Local Node
In the Cluster Status node list, Local node will be shown next to the node that the end user is currently accessing. If you are directly accessing the server via its designated IP or host name (instead of through a load balancer), this will always reflect the actual virtual or physical machine you have installed this platform cluster node on. If you are accessing the node through a load balancer, the local node might be different every time you reload the page, depending on which kind of load balancing strategy you have configured. While accessing a cluster node you will only ever be able to see the log files for the server that is indicated as local, and all interactions are processed by the respective local node.
Lead Node
Lead node indicates the oldest running node in the cluster, and this designation means that the node has specific responsibilities that should only be performed by at most one node in the cluster. This includes among others.
Running upgrade scripts
Sending emails
Processing Scheduled Cycles
Scheduled LDAP imports
If the lead node ever goes down or is restarted, the next oldest node in the cluster will automatically become the lead node. Aside from these special duties, the lead node can be treated like any other node in your High-Availability or horizontal scaling setup.