Configuring Solr for HADR

<solr-nodes>
  <solr-node
    memory="2g"
    data-dir="C:/i2/i2analyze/data/solr"
    host-name="solr_server1_host_name"
    id="node1"
    port-number="8983"
    />
  <solr-node
    memory="2g"
    data-dir="C:/i2/i2analyze/data/solr"
    host-name="solr_server2_host_name"
    id="node2"
    port-number="8983"
    />
</solr-nodes>

Where solr_serverx_host_name is the hostname of a Solr server.

For more information about the possible values for each attribute, see Solr and ZooKeeper.

The replication factor is the number of replicas to be created for each shard. For high availability, this must be 2 or more. You specify the replication factor in the num-replicas attribute of the <solr-collection> element.

The minimum replication factor defines when data is successfully replicated in Solr. If you have three replicas for a shard and a minimum replication factor of 2, a write operation is deemed successful if the data is written to at least two replicas. You specify the minimum replication factor in the min-replication-factor attribute of the <solr-collection> element.

The following extract from a topology.xml file shows an example of the num-replicas and min-replication-factor attributes:

<solr-collections>
  <solr-collection 
    num-replicas="2"
    min-replication-factor="1"
    id="main_index"
    type="main"
    max-shards-per-node="4"
    num-shards="1"
    />
  ...
</solr-collections>

To ensure that your system can still operate if a Solr server or node fails, you must ensure that there is at least on replica of each shard still available. To do this, you can create a replica placement policy to specify that each replica of a shard must be placed on a distinct host.

• Create the configuration\environment\opal-server\solr.autoscaling.policy.json file.
• In the file, provide your Solr autoscaling policies. For more information about the policies, see Autoscaling Policy and Preferences.
• To create a cluster policy that creates each replica of a shard on a distinct host, add the following lines to the file:

  {
     "set-cluster-policy":[
        {
           "replica":"<2",
           "shard":"#EACH",
           "host":"#EACH"
        }
     ]
  }

• The cluster policy is set when you create the Solr cluster as part of the deployment steps. Additionally, you can update the cluster policy by running the setSolrAutoscalingClusterPolicy toolkit task.