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/telemetry/client.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"net/http"
+	"sync"
 	"time"
 
 	"github.com/google/uuid"
@@ -17,6 +18,8 @@ type Client struct {
 	enabled    bool
 	instanceID string
 	httpClient *http.Client
+	topologyId string
+	sync.RWMutex
 }
 
 // NewClient creates a new telemetry client
@@ -31,6 +34,12 @@ func NewClient(url string, enabled bool) *Client {
 	}
 }
 
+func (c *Client) SetTopologyId(topologyId string) {
+	c.Lock()
+	defer c.Unlock()
+	c.topologyId = topologyId
+}
+
 // IsEnabled returns whether telemetry is enabled
 func (c *Client) IsEnabled() bool {
 	return c.enabled && c.url != ""
@@ -42,10 +51,20 @@ func (c *Client) SendTelemetry(data *proto.TelemetryData) error {
 		return nil
 	}
 
-	// Set the cluster ID
-	data.ClusterId = c.instanceID
+	// Work on a copy to avoid mutating the caller's TelemetryData
+	clonedData, ok := protobuf.Clone(data).(*proto.TelemetryData)
+	if !ok {
+		return fmt.Errorf("failed to clone telemetry data")
+	}
 
-	return c.sendProtobuf(data)
+	// Set the topology ID
+	c.RLock()
+	if c.topologyId != "" {
+		clonedData.TopologyId = c.topologyId
+	}
+	c.RUnlock()
+
+	return c.sendProtobuf(clonedData)
 }
 
 // SendTelemetryAsync sends telemetry data asynchronously