Feature: add state machine range and subscribe API

common/meta/raft-store/src/state_machine/sm.rs

@@ -90,6 +90,12 @@ const SEQ_DATABASE_META_ID: &str = "database_meta_id";
 // const TREE_META: &str = "meta";
 const TREE_STATE_MACHINE: &str = "state_machine";
 
+/// StateMachine subscriber trait
+#[async_trait::async_trait]
+pub trait StateMachineSubscriber: Debug + Sync + Send {
+    async fn kv_changed(&self, key: &str, prev: &Option<SeqV>, meta: &Option<SeqV>);
+}
+
 /// The state machine of the `MemStore`.
 /// It includes user data and two raft-related informations:
 /// `last_applied_logs` and `client_serial_responses` to achieve idempotence.
@@ -99,6 +105,9 @@ pub struct StateMachine {
     /// - Store initialization state and last applied in keyspace `StateMachineMeta`.
     /// - Every other state is store in its own keyspace such as `Nodes`.
     pub sm_tree: SledTree,
+
+    /// subscriber of statemachine data
+    pub subscriber: Option<Box<dyn StateMachineSubscriber>>,
 }
 
 /// A key-value pair in a snapshot is a vec of two `Vec<u8>`.
@@ -149,7 +158,10 @@ impl StateMachine {
 
         let sm_tree = SledTree::open(&db, &tree_name, config.is_sync())?;
 
-        let sm = StateMachine { sm_tree };
+        let sm = StateMachine {
+            sm_tree,
+            subscriber: None,
+        };
 
         let inited = {
             let sm_meta = sm.sm_meta();
@@ -167,6 +179,10 @@ impl StateMachine {
         }
     }
 
+    pub fn set_subscriber(&mut self, subscriber: Box<dyn StateMachineSubscriber>) {
+        self.subscriber = Some(subscriber);
+    }
+
     /// Create a snapshot.
     ///
     /// Returns:
@@ -344,10 +360,10 @@ impl StateMachine {
         let db_id = self.txn_incr_seq(SEQ_DATABASE_ID, txn_tree)?;
 
         let db_lookup_tree = txn_tree.key_space::<DatabaseLookup>();
-
+        let db_key = DatabaseLookupKey::new(tenant.to_string(), name.to_string());
         let (prev, result) = self.txn_sub_tree_upsert(
             &db_lookup_tree,
-            &DatabaseLookupKey::new(tenant.to_string(), name.to_string()),
+            &db_key,
             &MatchSeq::Exact(0),
             Operation::Update(db_id),
             None,
@@ -405,13 +421,9 @@ impl StateMachine {
     ) -> MetaStorageResult<AppliedState> {
         let dbs = txn_tree.key_space::<DatabaseLookup>();
 
-        let (prev, result) = self.txn_sub_tree_upsert(
-            &dbs,
-            &DatabaseLookupKey::new(tenant.to_string(), name.to_string()),
-            &MatchSeq::Any,
-            Operation::Delete,
-            None,
-        )?;
+        let db_key = DatabaseLookupKey::new(tenant.to_string(), name.to_string());
+        let (prev, result) =
+            self.txn_sub_tree_upsert(&dbs, &db_key, &MatchSeq::Any, Operation::Delete, None)?;
 
         assert!(
             result.is_none(),
@@ -466,6 +478,7 @@ impl StateMachine {
         if result.is_some() {
             self.txn_incr_seq(SEQ_DATABASE_META_ID, txn_tree)?;
         }
+
         Ok(AppliedState::TableMeta(Change::new_with_id(
             table_id.unwrap(),
             prev,
@@ -490,6 +503,7 @@ impl StateMachine {
         if result.is_none() {
             self.txn_incr_seq(SEQ_DATABASE_META_ID, txn_tree)?;
         }
+
         Ok(Change::new_with_id(table_id.unwrap(), prev, result).into())
     }
 
@@ -530,6 +544,7 @@ impl StateMachine {
             new_db_name,
             new_table_name
         );
+
         Ok(AppliedState::TableMeta(Change::new_with_id(
             new_table_id.unwrap(),
             prev,
@@ -547,15 +562,21 @@ impl StateMachine {
         txn_tree: &TransactionSledTree,
     ) -> MetaStorageResult<AppliedState> {
         let sub_tree = txn_tree.key_space::<GenericKV>();
+        let key_str = key.to_string();
         let (prev, result) = self.txn_sub_tree_upsert(
             &sub_tree,
-            &key.to_string(),
+            &key_str,
             seq,
             value_op.clone(),
             value_meta.clone(),
         )?;
 
         tracing::debug!("applied UpsertKV: {} {:?}", key, result);
+
+        if let Some(subscriber) = &self.subscriber {
+            let _ = subscriber.kv_changed(&key_str, &prev, &result);
+        }
+
         Ok(Change::new(prev, result).into())
     }