epugh commented on code in PR #977: URL: https://github.com/apache/solr/pull/977#discussion_r949104135
########## dev-docs/shard-split/shard-split.adoc: ########## @@ -0,0 +1,159 @@ += Shard Split +:toc: macro +:toclevels: 3 + +The document explains how shard split works in SolrCloud at a high level. + +toc::[] + +== Background +Constantly adding new documents to Solr will slow down query performance as index size increases. To handle this, shard split is introduced. Shard split feature works in both Standalone and SolrCloud modes. + +Shard is a logical partition of collection, containing a subset of documents from collection. Which shard contains which document depends on the sharding strategy. It is the "router" that determines this -- e.g. "implicit" vs "compositeId" When a document is sent to Solr for indexing, the system first determines which shard the document belongs to and finds a leader of that shard. Then the leader forwards the updates to other replicas. + +== Shard States +Shard can have one of the following states: + +* ACTIVE +** shard receives updates, participates in distributed search. +* CONSTRUCTION +** shard receives updates only from the parent shard leader, but doesn’t participate in distributed search. +** shard is put in that state when shard split operation is in progress or shard is undergoing data restoration. +* RECOVERY +** shard receives updates only from the parent shard leader, but doesn’t participate in distributed search. +** shard is put in that state to create replicas in order to meet collection’s replicationFactor. +* RECOVERY_FAILED +** shard doesn’t receive any updates, doesn’t participate in distributed search. +** shard is put in that state when parent shard leader is not live. +* INACTIVE +** shard is put in that state after it has been successfully split. + +Detail: Shard is referred to Slice in the codebase context. Review Comment: Boo..... ;-) And I didn't know this at all! -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@solr.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@solr.apache.org For additional commands, e-mail: issues-h...@solr.apache.org
