Clustering refers to running an application in multiple worker processes (workers), all receiving requests on the same port.
When StrongLoop Process Manager (PM) runs an application, it automatically runs it in a cluster with a number of workers equal to the number of CPU cores on the system. When you deploy an application with Arc, you can run the application in a multi-process cluster: simply enter the number of processes to run in the Build & Deploy module. See Building and deploying with Arc for details.
If any one process in a cluster is terminated or dies due to application error, StrongLoop Process Manager automatically starts up another process and attaches it to the cluster without having to restart the application, thus providing zero application downtime. If you inadvertently push a faulty deployment to a cluster, StrongLoop PM ensures rolling restarts: If the first process being restarted crashes, then the deployment is not pushed out to the remaining processes in the cluster.
You can control application clusters with Arc and with