FrankChen021 opened a new issue #10329:
URL: https://github.com/apache/druid/issues/10329


   ### Description
   
   Add support to show leader coordinator in `Services` web console view
   
   ### Motivation
   
   As we know, compared with standby coordinators, leader of coordinators does 
a lot of tasks such as checking whether to launch compaction tasks. To check 
whether these tasks are being processed correctly when debugging or solving 
problems, the first thing is to determine which coordinator right now is the 
leader.
   
   Currently, there's no way to know which coordinator is the leader from the 
web console ui. One has to use `/druid/indexer/v1/leader` RESTful API to send 
request to any coordinator nodes to get the information of leader. It's not a 
intuitive way for users.
   
   So, this proposal aims to simplify this by indicating which coordinator is 
leader on the web console.
   
   There's two ways achieve this: 
   
   ### Alternative 1
   
   When switching to the `Services` view on web console, the frontend calls the 
`/druid/indexer/v1/leader` API to get the leader and then show the result in 
the `Tier` column of corresponding row in that view.
   
   This is like the way current web console ui uses to show the last task 
status of middle manager in `Services` view
   
   ##### The Pros
   
   No backend changes are involved.
   
   ##### The Cons
   
   `/druid/indexer/v1/leader` must be sent to the coordinator, but the frontend 
can't sent this request util it gets services list from router through SQL 
query to know where coordinators locate. It's a little bit complex for the 
frontend.
   
   ### Alternative 2
   
   When processing query on `sys.servers` table, broker calls 
`/druid/indexer/v1/leader` to get the leader and mark the leader coordinator in 
`tier` field. The frontend ui will automatically show the leader once there's 
value in `tier` property.
   
   ##### The Pros
   
   No changes are involved in frontend but backend services. 
   
   
   Any discussion would be appreciated. 
   


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