Change: RaftState: add field snapshot_meta

Snapshot meta should be part of the `RaftState`.
Move it from `Engine` to `RaftState`

openraft/src/core/raft_core.rs

@@ -207,12 +207,6 @@ impl<C: RaftTypeConfig, N: RaftNetworkFactory<C>, S: RaftStorage<C>> RaftCore<C,
             purge_batch_size: self.config.purge_batch_size,
         });
 
-        // Fetch the most recent snapshot in the system.
-        if let Some(snapshot) = self.storage.get_current_snapshot().await? {
-            self.engine.snapshot_meta = snapshot.meta;
-            self.engine.metrics_flags.set_data_changed();
-        }
-
         self.engine.startup();
         // No output commands
 
@@ -639,7 +633,7 @@ impl<C: RaftTypeConfig, N: RaftNetworkFactory<C>, S: RaftStorage<C>> RaftCore<C,
             current_term: self.engine.state.vote.term,
             last_log_index: self.engine.state.last_log_id().map(|id| id.index),
             last_applied: self.engine.state.committed,
-            snapshot: self.engine.snapshot_meta.last_log_id,
+            snapshot: self.engine.state.snapshot_meta.last_log_id,
 
             // --- cluster ---
             state: self.engine.state.server_state,
@@ -752,7 +746,7 @@ impl<C: RaftTypeConfig, N: RaftNetworkFactory<C>, S: RaftStorage<C>> RaftCore<C,
 
         if !force {
             // If we are below the threshold, then there is nothing to do.
-            if self.engine.state.committed.next_index() - self.engine.snapshot_meta.last_log_id.next_index()
+            if self.engine.state.committed.next_index() - self.engine.state.snapshot_meta.last_log_id.next_index()
                 < *threshold
             {
                 return;

openraft/src/engine/calc_purge_upto_test.rs

@@ -62,7 +62,7 @@ fn test_calc_purge_upto() -> anyhow::Result<()> {
         if let Some(last_purged) = last_purged {
             eng.state.log_ids.purge(&last_purged);
         }
-        eng.snapshot_meta.last_log_id = snapshot_last_log_id;
+        eng.state.snapshot_meta.last_log_id = snapshot_last_log_id;
         let got = eng.calc_purge_upto();
 
         assert_eq!(

openraft/src/engine/engine_impl.rs

@@ -71,9 +71,6 @@ where
 
     pub(crate) config: EngineConfig,
 
-    /// The metadata of the last snapshot.
-    pub(crate) snapshot_meta: SnapshotMeta<NID, N>,
-
     /// The state of this raft node.
     pub(crate) state: RaftState<NID, N>,
 
@@ -93,7 +90,6 @@ where
         Self {
             id,
             config,
-            snapshot_meta: Default::default(),
             state: init_state.clone(),
             metrics_flags: MetricsChangeFlags::default(),
             commands: vec![],
@@ -575,18 +571,18 @@ where
         let max_keep = self.config.max_in_snapshot_log_to_keep;
         let batch_size = self.config.purge_batch_size;
 
-        let purge_end = self.snapshot_meta.last_log_id.next_index().saturating_sub(max_keep);
+        let purge_end = self.state.snapshot_meta.last_log_id.next_index().saturating_sub(max_keep);
 
         tracing::debug!(
-            snapshot_last_log_id = debug(self.snapshot_meta.last_log_id),
+            snapshot_last_log_id = debug(self.state.snapshot_meta.last_log_id),
             max_keep,
             "try purge: (-oo, {})",
             purge_end
         );
 
         if st.last_purged_log_id().next_index() + batch_size > purge_end {
             tracing::debug!(
-                snapshot_last_log_id = debug(self.snapshot_meta.last_log_id),
+                snapshot_last_log_id = debug(self.state.snapshot_meta.last_log_id),
                 max_keep,
                 last_purged_log_id = display(st.last_purged_log_id().summary()),
                 batch_size,
@@ -893,16 +889,16 @@ where
     pub(crate) fn update_snapshot(&mut self, meta: SnapshotMeta<NID, N>) -> bool {
         tracing::info!("update_snapshot: {:?}", meta);
 
-        if meta.last_log_id <= self.snapshot_meta.last_log_id {
+        if meta.last_log_id <= self.state.snapshot_meta.last_log_id {
             tracing::info!(
                 "No need to install a smaller snapshot: current snapshot last_log_id({}), new snapshot last_log_id({})",
-                self.snapshot_meta.last_log_id.summary(),
+                self.state.snapshot_meta.last_log_id.summary(),
                 meta.last_log_id.summary()
             );
             return false;
         }
 
-        self.snapshot_meta = meta;
+        self.state.snapshot_meta = meta;
         self.metrics_flags.set_data_changed();
 
         true

openraft/src/engine/install_snapshot_test.rs

@@ -29,14 +29,7 @@ fn m1234() -> Membership<u64, ()> {
 }
 
 fn eng() -> Engine<u64, ()> {
-    let mut eng = Engine::<u64, ()> {
-        snapshot_meta: SnapshotMeta {
-            last_log_id: Some(log_id(2, 2)),
-            last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m12()),
-            snapshot_id: "1-2-3-4".to_string(),
-        },
-        ..Default::default()
-    };
+    let mut eng = Engine::<u64, ()> { ..Default::default() };
 
     eng.state.committed = Some(log_id(4, 5));
     eng.state.log_ids = LogIdList::new(vec![
@@ -46,6 +39,11 @@ fn eng() -> Engine<u64, ()> {
         log_id(4, 6),
         log_id(4, 8),
     ]);
+    eng.state.snapshot_meta = SnapshotMeta {
+        last_log_id: Some(log_id(2, 2)),
+        last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m12()),
+        snapshot_id: "1-2-3-4".to_string(),
+    };
     eng.state.server_state = eng.calc_server_state();
 
     eng
@@ -68,7 +66,7 @@ fn test_install_snapshot_lt_last_snapshot() -> anyhow::Result<()> {
             last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m12()),
             snapshot_id: "1-2-3-4".to_string(),
         },
-        eng.snapshot_meta
+        eng.state.snapshot_meta
     );
 
     assert_eq!(
@@ -113,7 +111,7 @@ fn test_install_snapshot_lt_committed() -> anyhow::Result<()> {
             last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m12()),
             snapshot_id: "1-2-3-4".to_string(),
         },
-        eng.snapshot_meta
+        eng.state.snapshot_meta
     );
 
     assert_eq!(
@@ -156,7 +154,7 @@ fn test_install_snapshot_not_conflict() -> anyhow::Result<()> {
             last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m1234()),
             snapshot_id: "1-2-3-4".to_string(),
         },
-        eng.snapshot_meta
+        eng.state.snapshot_meta
     );
     assert_eq!(&[log_id(4, 6), log_id(4, 8)], eng.state.log_ids.key_log_ids());
     assert_eq!(Some(log_id(4, 6)), eng.state.committed);
@@ -200,14 +198,7 @@ fn test_install_snapshot_conflict() -> anyhow::Result<()> {
     // Snapshot will be installed, all non-committed log will be deleted.
     // And there should be no conflicting logs left.
     let mut eng = {
-        let mut eng = Engine::<u64, ()> {
-            snapshot_meta: SnapshotMeta {
-                last_log_id: Some(log_id(2, 2)),
-                last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m12()),
-                snapshot_id: "1-2-3-4".to_string(),
-            },
-            ..Default::default()
-        };
+        let mut eng = Engine::<u64, ()> { ..Default::default() };
 
         eng.state.committed = Some(log_id(2, 3));
         eng.state.log_ids = LogIdList::new(vec![
@@ -218,6 +209,12 @@ fn test_install_snapshot_conflict() -> anyhow::Result<()> {
             log_id(4, 8),
         ]);
 
+        eng.state.snapshot_meta = SnapshotMeta {
+            last_log_id: Some(log_id(2, 2)),
+            last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m12()),
+            snapshot_id: "1-2-3-4".to_string(),
+        };
+
         eng.state.server_state = eng.calc_server_state();
 
         eng
@@ -235,7 +232,7 @@ fn test_install_snapshot_conflict() -> anyhow::Result<()> {
             last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m1234()),
             snapshot_id: "1-2-3-4".to_string(),
         },
-        eng.snapshot_meta
+        eng.state.snapshot_meta
     );
     assert_eq!(&[log_id(5, 6)], eng.state.log_ids.key_log_ids());
     assert_eq!(Some(log_id(5, 6)), eng.state.committed);
@@ -292,7 +289,7 @@ fn test_install_snapshot_advance_last_log_id() -> anyhow::Result<()> {
             last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m1234()),
             snapshot_id: "1-2-3-4".to_string(),
         },
-        eng.snapshot_meta
+        eng.state.snapshot_meta
     );
     assert_eq!(&[log_id(100, 100)], eng.state.log_ids.key_log_ids());
     assert_eq!(Some(log_id(100, 100)), eng.state.committed);

openraft/src/engine/update_snapshot_test.rs

@@ -25,14 +25,14 @@ fn m1234() -> Membership<u64, ()> {
 }
 
 fn eng() -> Engine<u64, ()> {
-    Engine::<u64, ()> {
-        snapshot_meta: SnapshotMeta {
-            last_log_id: Some(log_id(2, 2)),
-            last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m12()),
-            snapshot_id: "1-2-3-4".to_string(),
-        },
-        ..Default::default()
-    }
+    let mut eng = Engine::<u64, ()> { ..Default::default() };
+
+    eng.state.snapshot_meta = SnapshotMeta {
+        last_log_id: Some(log_id(2, 2)),
+        last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m12()),
+        snapshot_id: "1-2-3-4".to_string(),
+    };
+    eng
 }
 
 #[test]
@@ -54,7 +54,7 @@ fn test_update_snapshot_no_update() -> anyhow::Result<()> {
             last_membership: EffectiveMembership::new(Some(log_id(1, 1)), m12()),
             snapshot_id: "1-2-3-4".to_string(),
         },
-        eng.snapshot_meta
+        eng.state.snapshot_meta
     );
 
     assert_eq!(
@@ -90,7 +90,7 @@ fn test_update_snapshot_updated() -> anyhow::Result<()> {
             last_membership: EffectiveMembership::new(Some(log_id(2, 2)), m1234()),
             snapshot_id: "1-2-3-4".to_string(),
         },
-        eng.snapshot_meta
+        eng.state.snapshot_meta
     );
 
     assert_eq!(

openraft/src/raft_state.rs

@@ -8,6 +8,7 @@ use crate::LogIdOptionExt;
 use crate::MembershipState;
 use crate::NodeId;
 use crate::ServerState;
+use crate::SnapshotMeta;
 use crate::Vote;
 
 /// A struct used to represent the raft state which a Raft node needs.
@@ -33,6 +34,9 @@ where
     /// The latest cluster membership configuration found, in log or in state machine.
     pub membership_state: MembershipState<NID, N>,
 
+    /// The metadata of the last snapshot.
+    pub snapshot_meta: SnapshotMeta<NID, N>,
+
     // --
     // -- volatile fields: they are not persisted.
     // --

openraft/src/storage/helper.rs

@@ -56,13 +56,16 @@ where
 
         let log_ids = LogIdList::load_log_ids(last_purged_log_id, last_log_id, self).await?;
 
+        let snapshot_meta = self.sto.get_current_snapshot().await?.map(|x| x.meta).unwrap_or_default();
+
         Ok(RaftState {
             committed: last_applied,
             // The initial value for `vote` is the minimal possible value.
             // See: [Conditions for initialization](https://datafuselabs.github.io/openraft/cluster-formation.html#conditions-for-initialization)
             vote: vote.unwrap_or_default(),
             log_ids,
             membership_state: mem_state,
+            snapshot_meta,
 
             // -- volatile fields: they are not persisted.
             internal_server_state: InternalServerState::default(),