Many services in HDP depend on core services such as Apache Solr for indexing data. For example, Atlas uses indexing services for tagging lineage free text search, and Ranger uses indexing for audit data. The role of Ambari Infra is to provide these common shared services for stack components.

In this release, the Ambari Infra Service has only one component, the Infra Solr Instance. The Infra Solr Instance is a fully managed Apache Solr installation. By default, a single-node SolrCloud installation is deployed when the Ambari Infra Service is chosen for installation, but Hortonworks recommends that you install multiple Infra Solr Instances in order to provide distributed indexing and search for Atlas, Ranger, and LogSearch (Technical Preview).This can be accomplished by simply adding additional Ambari Infra Solr Instances to existing cluster hosts through Ambari’s +Add Service capability. The number of Infra Solr Instances to deploy is dependent on the number of nodes in the cluster and the services deployed.

Due to the fact that the Ambari Infra Solr Instance is used by multiple HDP components, you should be careful when restarting the service to avoid disrupting those dependent services. In HDP 2.5, Atlas, Ranger, and Log Search (Technical Preview) are dependent on the Ambari Infra Service.

	Note
	The Infra Solr Instance is only intended for use by HDP components; Hortonworks does not support the use of the Infra Solr Instance by third party components or applications.