* Fix master leader election startup issue
Fixes #error-log-leader-not-selected-yet
* Fix master leader election startup issue
This change improves server address comparison using the 'Equals' method and handles recursion in topology leader lookup, resolving the 'leader not selected yet' error during master startup.
* Merge user improvements: use MaybeLeader for non-blocking checks
* not useful test
* Address code review: optimize Equals, fix deadlock in IsLeader, safe access in Leader
* Prevent split-brain: Persistent ClusterID and Join Validation
- Persist ClusterId in Raft store to survive restarts.
- Validate ClusterId on Raft command application (piggybacked on MaxVolumeId).
- Prevent masters with conflicting ClusterIds from joining/operating together.
- Update Telemetry to report the persistent ClusterId.
* Refine ClusterID validation based on feedback
- Improved error message in cluster_commands.go.
- Added ClusterId mismatch check in RaftServer.Recovery.
* Handle Raft errors and support Hashicorp Raft for ClusterId
- Check for errors when persisting ClusterId in legacy Raft.
- Implement ClusterId generation and persistence for Hashicorp Raft leader changes.
- Ensure consistent error logging.
* Refactor ClusterId validation
- Centralize ClusterId mismatch check in Topology.SetClusterId.
- Simplify MaxVolumeIdCommand.Apply and RaftServer.Recovery to rely on SetClusterId.
* Fix goroutine leak and add timeout
- Handle channel closure in Hashicorp Raft leader listener.
- Add timeout to Raft Apply call to prevent blocking.
* Fix deadlock in legacy Raft listener
- Wrap ClusterId generation/persistence in a goroutine to avoid blocking the Raft event loop (deadlock).
* Rename ClusterId to SystemId
- Renamed ClusterId to SystemId across the codebase (protobuf, topology, server, telemetry).
- Regenerated telemetry.pb.go with new field.
* Rename SystemId to TopologyId
- Rename to SystemId was intermediate step.
- Final name is TopologyId for the persistent cluster identifier.
- Updated protobuf, topology, raft server, master server, and telemetry.
* Optimize Hashicorp Raft listener
- Integrated TopologyId generation into existing monitorLeaderLoop.
- Removed extra goroutine in master_server.go.
* Fix optimistic TopologyId update
- Removed premature local state update of TopologyId in master_server.go and raft_hashicorp.go.
- State is now solely updated via the Raft state machine Apply/Restore methods after consensus.
* Add explicit log for recovered TopologyId
- Added glog.V(0) info log in RaftServer.Recovery to print the recovered TopologyId on startup.
* Add Raft barrier to prevent TopologyId race condition
- Implement ensureTopologyId helper method
- Send no-op MaxVolumeIdCommand to sync Raft log before checking TopologyId
- Ensures persisted TopologyId is recovered before generating new one
- Prevents race where generation happens during log replay
* Serialize TopologyId generation with mutex
- Add topologyIdGenLock mutex to MasterServer struct
- Wrap ensureTopologyId method with lock to prevent concurrent generation
- Fixes race where event listener and manual leadership check both generate IDs
- Second caller waits for first to complete and sees the generated ID
* Add TopologyId recovery logging to Apply method
- Change log level from V(1) to V(0) for visibility
- Log 'Recovered TopologyId' when applying from Raft log
- Ensures recovery is visible whether from snapshot or log replay
- Matches Recovery() method logging for consistency
* Fix Raft barrier timing issue
- Add 100ms delay after barrier command to ensure log application completes
- Add debug logging to track barrier execution and TopologyId state
- Return early if barrier command fails
- Prevents TopologyId generation before old logs are fully applied
* ensure leader
* address comments
* address comments
* redundant
* clean up
* double check
* refactoring
* comment
`topology.Leader()` was using a backoff that typically
resulted in at least a 5s delay when initially starting
a master and raft server. This changes the backoff
algorithm to use exponential backoff starting with 100ms
and waiting up to 20s for leader selection.
Related to #4307
1, there will be two leader when master server startup in a few seconds
2, raft server will get a leader even there is only one master, so there is no need to do hard code to set the server to be leader
