Page History

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• Ability to specify node roles in Solr. This release supports 'Overseer' and 'Data' roles out of the box.
• New API for pluggable replica assignment implementations
• Distributed Overseer (optional) allows for distributed processing of cluster state updates and Collection and Config API call processing without relying on the Overseer.

Others

• Admin UI support for SQL Querying
• HDFS code is now an independent module
• Metrics handler only depends on SolrJ instead of core and has its own log4j2.xml now so it doesn’t share Solr’s logging config

Build

• Solr is now built and released independently from Lucene (separate Apache projects)
• Build system switched to Gradle, no longer uses Ant + Ivy

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• Image creation is now a part of the Apache Solr Github repo
• Solr Docker image documentation is now a part of the reference guide
• Official image upgraded to use JDK17 (by Eclipse Temurin) and ability to create functionally identical local image

Others

• Admin UI support for SQL Querying
• HDFS code is now an independent module
• Metrics handler only depends on SolrJ instead of core and has its own log4j2.xml now so it doesn’t share Solr’s logging config

Deprecations and Removal

• Data Import Handler has been removed from Solr
• Legacy cloud mode is no longer supported
• No more support for clusterstate.json and MIGRATESTATE API has been removed. If your collections use clusterstate.json, please refer to the upgrade notes
• Auto scaling framework has been removed. Please refer to replica placement plugins for alternate options
• LegacyBM25SimilarityFactory has been removed
• VelocityResponseWriter has been removed from Solr. This encompasses all previous included /browse and wt=velocity examples.
• Legacy SolrCache implementations (LRUCache, LFUCache, FastLRUCache) have been removed. Users have to modify their existing configurations to use CaffeineCache instead.
• Cross Data Center Replication has been removed in this released.

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