Clusters and Replicas: Standalone or Resilient

Standalone or cluster

An index made with Add New Index is standalone: it lives on one server and has no replica servers. A resilient cluster keeps the same index on three servers, so it keeps answering when one of them fails.

01 · How a cluster works

One address for your app. Writes go to the master, searches are spread over all three, and the replicas copy the master.

A cluster lives on at least three servers: one master and two replicas, with reads kept apart from writes and the load spread between them. Your app connects to the Host shown on the Info tab of the master: Connect to your index.

02 · Create a cluster

In the top menu open Solr > Add New Cluster. The page is titled High-Availability, Resilient Clusters.
Select Environment: the region and Solr version of the cluster.
Cluster Name: letters and digits only; other characters, the underscore included, are removed.
Solr config. archive (optional): a ZIP with your configuration files, if you have one.
Click Add Cluster. Opensolr creates the master and its two replicas.

Your plan sets how many clusters you can have. Past that number the page says it “Can not add more than” your count, with a link to upgrade: Pricing. For fully dedicated cluster servers, the page has Request Your Private Cluster Environment.

03 · Running a cluster

You manage the cluster from the control panel of the master. Its Info tab lists the Replica Servers, and the left menu adds Cluster Wide Stats and Delete Cluster.
A configuration ZIP uploaded on the master, and a solrconfig.xml saved on it, are written to the replicas too.
The Bandwidth card of the master adds up the master and its replicas: Bandwidth.
Solr > Cluster List lists your clusters.

04 · Copies of a standalone index

A standalone index gets no replica servers. To keep a copy of it on another index of yours, use Replicate an index.

More: Resilient Solr Clusters, Shared, Dedicated and Resilient Cluster solutions, and by API API: Create Resilient Cluster.