Details
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Improvement
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Status: Closed
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Major
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Resolution: Fixed
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None
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Description
Solr 8x replica placement provided two settings that are very useful in certain scenarios:
- withCollection constraint specified that replicas should be placed on the same nodes where replicas of another collection are located. In the 8x implementation this was limited in practice to co-locating single-shard secondary collections used for joins or other lookups from the main collection (which could be multi-sharded).
- maxShardsPerNode - this constraint specified the maximum number of replicas per shard that can be placed on the same node. In most scenarios this was set to 1 in order to ensure fault-tolerance (ie. at most 1 replica of any given shard would be placed on any given node). Changing this constraint to values > 1 would reduce fault-tolerance but may be desired in test setups or as a temporary relief measure.
Both these constraints are collection-specific so they should be configured e.g. as collection properties.
Edit: maxShardsPerNode constraint will be addressed in another issue.
