[SOLR-11521] suggestions to add more nodes when rules are broken

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Component/s: AutoScaling
• Assignee: Unassigned
• Reporter: Noble Paul
• Created: 21/Oct/17 00:39
• Updated: 14/Aug/21 01:33
• Resolved: 14/Aug/21 01:33

Description

In a given cluster it is possible that some policy rules are broken (a violation) and Solr cannot make any suggestion without breaking any rules. In such a scenario, The suggestion framework would perform the following steps 

1. Check if there are violations and try to make suggestions to existing nodes, if not possible
2. Simulate addition of a new extra node
3. Go to step #1 assuming this simulated node is present in the list of nodes
4. There are 3 possibilities
   1. The violation is completely gone
   2. The violation has become less serious
   3. The violation has not come down or it has become more serious
5. In case of #4.1 recommend to add a single node (or multiple nodes depending upon the no:of evaluations). Present a suggestion with
   • The list of violations. It contains information the policy rule and the actual node/replica that is causing violation
     #*No:of nodes to be added
6. In case of #4.1 it may mean that adding more nodes can help improve the situation , So Go to step #2
7. In case of #4.3 this violation is not not solvable. present a suggestion with the following information
   • The list of violations. It contains information the policy rule and the actual node/replica that is causing violation
   • A message to review the policy rules