High Availability for Search
Search delivers key high availability features such as zero downtime administration and maintenance, built-in optional data redundancy, and manual failover.
Factors that increase system uptime and availability include:
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Number of replicas
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Number of racks or availability zones
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Index alias
High Availability Indexes
High availability indexes help users prevent downtime caused by unplanned incidents and enhance the overall system availability. It is achieved through Replica and Failover mechanisms with Search Service.
Replica for the index is not automatically enabled. The user must explicitly configure the required number of replicas for the index partitions according to their availability needs during the index creation step. Refer Index Replicas to the index replica section during index creation. They could also update the replica count without rebuilding the primary partitions or live traffic for an existing index.
Server Groups/Rack zone awareness - a Server Group is a logical group of nodes. It can be based on their physical location in the network. Server Group awareness ensures that active and replica partitions are automatically assigned to different server groups(racks). So that, if a physical rack fails, the replica partition remains safe and available in another rack. Starting with Couchbase Server release 7.0.2, the Search service supports Server Groups/Rack zone aware replica placements.
Zero Downtime Index Upgrades
Users can update/recreate/rebuild the indexes without interfering with the live systems by leveraging the index-alias feature. The index aliases permit indirection in the index naming, whereby applications refer to an alias-name that never changes, leaving administrators free to change the identity of the real index pointed to by the alias. This may be particularly useful when an index needs to be updated: to avoid downtime, while the current index remains in service, a clone of the current index can be created, modified, and tested. Then, when the clone is ready, the existing alias can be retargeted so that the clone becomes the current index; and the (now) previous index can be removed.