[SOLR-12023] Autoscaling policy engine shuffles replicas needlessly and can also suggest nonexistent replicas to be moved

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 7.6, 8.0
• Component/s: AutoScaling, SolrCloud
• Assignee: Noble Paul
• Reporter: Shalin Shekhar Mangar
• Created: 23/Feb/18 03:55
• Updated: 02/Oct/19 17:24
• Resolved: 17/Jan/19 06:26

Description

A test that I wrote in SOLR-11066 found the following problem:

Cluster: 2 nodes
Collection: 1 shard, 3 replicas, maxShardsPerNode=5
No autoscaling policy or preference applied

When the trigger runs, the computed plan needlessly shuffles all three replicas and then proceeds to return suggestions with only numbers as core names. These cores do not exist. I found that these numbers are generated internally by the framework as placeholders for moved cores for further calculations. They should never ever be suggested to the users.

Issue Links

• blocks: SOLR-11066 Implement a scheduled trigger
• is duplicated by: SOLR-12116 Autoscaling suggests to move a replica that does not exist (all numbers)
• is related to: SOLR-12031 Refactor Policy framework to let state changes to be applied to all nodes