chore: apply suggestions from CR

src/meta-srv/src/error.rs

@@ -848,13 +848,6 @@ pub enum Error {
         #[snafu(source(from(common_config::error::Error, Box::new)))]
         source: Box<common_config::error::Error>,
     },
-
-    #[snafu(display("Region: {} leader peer is not found", region_id))]
-    RegionLeaderNotFound {
-        #[snafu(implicit)]
-        location: Location,
-        region_id: RegionId,
-    },
 }
 
 impl Error {
@@ -946,8 +939,7 @@ impl ErrorExt for Error {
             | Error::RegionOpeningRace { .. }
             | Error::RegionRouteNotFound { .. }
             | Error::MigrationAbort { .. }
-            | Error::MigrationRunning { .. }
-            | Error::RegionLeaderNotFound { .. } => StatusCode::Unexpected,
+            | Error::MigrationRunning { .. } => StatusCode::Unexpected,
             Error::TableNotFound { .. } => StatusCode::TableNotFound,
             Error::SaveClusterInfo { source, .. }
             | Error::InvalidClusterInfoFormat { source, .. } => source.status_code(),

src/meta-srv/src/metasrv/builder.rs

@@ -36,7 +36,6 @@ use common_meta::state_store::KvStateStore;
 use common_meta::wal_options_allocator::WalOptionsAllocator;
 use common_procedure::local::{LocalManager, ManagerConfig};
 use common_procedure::ProcedureManagerRef;
-use common_telemetry::warn;
 use snafu::ResultExt;
 
 use super::{SelectTarget, FLOW_ID_SEQ};
@@ -313,7 +312,10 @@ impl MetasrvBuilder {
         region_migration_manager.try_start()?;
 
         if !is_remote_wal && options.enable_region_failover {
-            warn!("Region failover is not supported in the local WAL implementation!");
+            return error::UnexpectedSnafu {
+                violated: "Region failover is not supported in the local WAL implementation!",
+            }
+            .fail();
         }
 
         let (region_failover_handler, region_supervisor_ticker) =

src/meta-srv/src/region/failure_detector.rs

@@ -70,7 +70,7 @@ impl RegionFailureDetector {
 
     /// Removes the specific [PhiAccrualFailureDetector] if exists.
     pub(crate) fn remove(&self, ident: &Ident) {
-        let _ = self.detectors.remove(ident);
+        self.detectors.remove(ident);
     }
 
     /// Removes all [PhiAccrualFailureDetector]s.

src/meta-srv/src/region/supervisor.rs

@@ -61,6 +61,18 @@ impl From<&Stat> for DatanodeHeartbeat {
     }
 }
 
+/// `Event` represents various types of events that can be processed by the region supervisor.
+/// These events are crucial for managing state transitions and handling specific scenarios
+/// in the region lifecycle.
+///
+/// Variants:
+/// - `Tick`: This event is used to trigger region failure detection periodically.
+/// - `HeartbeatArrived`: This event presents the metasrv received [`DatanodeHeartbeat`] from the datanodes.
+/// - `Clear`: This event is used to reset the state of the supervisor, typically used
+///   when a system-wide reset or reinitialization is needed.
+/// - `Dump`: (Available only in test) This event triggers a dump of the
+///   current state for debugging purposes. It allows developers to inspect the internal state
+///   of the supervisor during tests.
 pub(crate) enum Event {
     Tick,
     HeartbeatArrived(DatanodeHeartbeat),
@@ -112,8 +124,8 @@ impl RegionSupervisorTicker {
                 }
                 loop {
                     interval.tick().await;
-                    if let Err(err) = sender.send(Event::Tick).await {
-                        warn!(err; "EventReceiver is dropped, tick loop is stopped");
+                    if sender.send(Event::Tick).await.is_err() {
+                        info!("EventReceiver is dropped, tick loop is stopped");
                         break;
                     }
                 }
@@ -274,13 +286,7 @@ impl RegionSupervisor {
                 .remove(&(cluster_id, datanode_id, region_id));
         }
 
-        warn!(
-            "Detects region failures: {:?}",
-            regions
-                .iter()
-                .map(|(_, datanode, region)| (datanode, region))
-                .collect::<Vec<_>>()
-        );
+        warn!("Detects region failures: {:?}", regions);
         for (cluster_id, datanode_id, region_id) in regions {
             match self.do_failover(cluster_id, datanode_id, region_id).await {
                 Ok(_) => self