Prevent split-brain: Persistent ClusterID and Join Validation (#8022)

* 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

weed/server/raft_hashicorp.go

@@ -4,6 +4,7 @@ package weed_server
 // https://github.com/Jille/raft-grpc-example/blob/cd5bcab0218f008e044fbeee4facdd01b06018ad/application.go#L18
 
 import (
+	"encoding/json"
 	"fmt"
 	"math/rand/v2"
 	"os"
@@ -17,10 +18,12 @@ import (
 	"github.com/armon/go-metrics"
 	"github.com/armon/go-metrics/prometheus"
 	"github.com/hashicorp/raft"
+	hashicorpRaft "github.com/hashicorp/raft"
 	boltdb "github.com/hashicorp/raft-boltdb/v2"
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/pb"
 	"github.com/seaweedfs/seaweedfs/weed/stats"
+	"github.com/seaweedfs/seaweedfs/weed/topology"
 	"google.golang.org/grpc"
 )
 
@@ -72,6 +75,17 @@ func (s *RaftServer) monitorLeaderLoop(updatePeers bool) {
 
 				s.topo.DoBarrier()
 
+				EnsureTopologyId(s.topo, func() bool {
+					return s.RaftHashicorp.State() == hashicorpRaft.Leader
+				}, func(topologyId string) error {
+					command := topology.NewMaxVolumeIdCommand(s.topo.GetMaxVolumeId(), topologyId)
+					b, err := json.Marshal(command)
+					if err != nil {
+						return err
+					}
+					return s.RaftHashicorp.Apply(b, 5*time.Second).Error()
+				})
+
 				stats.MasterLeaderChangeCounter.WithLabelValues(fmt.Sprintf("%+v", leader)).Inc()
 			} else {
 				s.topo.BarrierReset()