satwik-pachigolla opened a new issue, #19081:
URL: https://github.com/apache/pinot/issues/19081

   Several Pinot workflows rely on broker routing converging with server-side 
segment state changes before the old serving path becomes unavailable. A stale 
routing entry can send a query to a server after that server has dropped the 
segment, producing SERVER_SEGMENT_MISSING.
   
   1. Server readiness versus broker readiness
   [Issue #16565](https://github.com/apache/pinot/issues/16565) describes a 
server returning healthy before brokers had resumed routing to it. During a 
rolling restart, this allowed the next server to be restarted while neither 
replica was queryable.
   
   2. Segment deletion / retention
   Deletion has the inverse ordering requirement. The controller updates 
IdealState, servers asynchronously process the resulting transition and remove 
the segment, and brokers asynchronously rebuild routing. If a broker routes a 
query using the old assignment after the server has removed the segment, the 
query fails.
   
   This is less likely for ordinary retention when time pruning excludes 
expired segments, but it remains possible for queries spanning the retention 
boundary and for explicit segment deletion.
   
   3. Rebalance transition
   Even with add-before-remove rebalance, a query can be dispatched immediately 
before the source server’s state transition reaches broker routing. If the 
source has removed the segment by request handling time, it returns:
   
   
   Query processing exceptions:
   {235=1 segments [<segment>] missing on server: <server>}
   The common requirement is that brokers must stop routing a segment to a 
server before that server drops the segment. An external workflow can enforce 
this by waiting until every broker routing table excludes the target segments 
before deletion; Pinot currently does not provide a controller-level 
acknowledgement or ordering guarantee for that invariant.


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