From 5eb9d3afd7a0b4fef13fd4b87b053bed09c91d9e Mon Sep 17 00:00:00 2001
From: drdr xp <drdr.xp@gmail.com>
Date: Fri, 9 Jul 2021 15:47:50 +0800
Subject: [PATCH] change: RaftCore: replace `snapshot_index` with
 `snapshot_last_included: LogId`. Keep tracks of both snapshot last log term
 and index.

Also `SnapshotUpdate::SnapshotComplete` now contains an LogId instead of an u64 index.
---
 async-raft/src/core/install_snapshot.rs |  2 +-
 async-raft/src/core/mod.rs              | 21 +++++++++++----------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/async-raft/src/core/install_snapshot.rs b/async-raft/src/core/install_snapshot.rs
index 06e6e3a5f..1abb5805c 100644
--- a/async-raft/src/core/install_snapshot.rs
+++ b/async-raft/src/core/install_snapshot.rs
@@ -185,7 +185,7 @@ impl<D: AppData, R: AppDataResponse, N: RaftNetwork<D>, S: RaftStorage<D, R>> Ra
         self.last_log_index = req.last_included.index;
         self.last_log_term = req.last_included.term;
         self.last_applied = req.last_included.index;
-        self.snapshot_index = req.last_included.index;
+        self.snapshot_last_included = req.last_included;
         Ok(())
     }
 }
diff --git a/async-raft/src/core/mod.rs b/async-raft/src/core/mod.rs
index be0ba0762..57b5a5132 100644
--- a/async-raft/src/core/mod.rs
+++ b/async-raft/src/core/mod.rs
@@ -112,10 +112,11 @@ pub struct RaftCore<D: AppData, R: AppDataResponse, N: RaftNetwork<D>, S: RaftSt
 
     /// The node's current snapshot state.
     snapshot_state: Option<SnapshotState<S::Snapshot>>,
-    /// The index of the current snapshot, if a snapshot exists.
+
+    /// The log id upto which the current snapshot includes, inclusive, if a snapshot exists.
     ///
     /// This is primarily used in making a determination on when a compaction job needs to be triggered.
-    snapshot_index: u64,
+    snapshot_last_included: LogId,
 
     /// A cache of entries which are waiting to be replicated to the state machine.
     ///
@@ -176,7 +177,7 @@ impl<D: AppData, R: AppDataResponse, N: RaftNetwork<D>, S: RaftStorage<D, R>> Ra
             last_log_index: 0,
             last_log_term: 0,
             snapshot_state: None,
-            snapshot_index: 0,
+            snapshot_last_included: LogId { term: 0, index: 0 },
             entries_cache: Default::default(),
             replicate_to_sm_handle: FuturesOrdered::new(),
             has_completed_initial_replication_to_sm: false,
@@ -211,7 +212,7 @@ impl<D: AppData, R: AppDataResponse, N: RaftNetwork<D>, S: RaftStorage<D, R>> Ra
         if let Some(snapshot) =
             self.storage.get_current_snapshot().await.map_err(|err| self.map_fatal_storage_error(err))?
         {
-            self.snapshot_index = snapshot.included.index;
+            self.snapshot_last_included = snapshot.included;
         }
 
         let has_log = self.last_log_index != u64::min_value();
@@ -407,8 +408,8 @@ impl<D: AppData, R: AppDataResponse, N: RaftNetwork<D>, S: RaftStorage<D, R>> Ra
     /// Update the system's snapshot state based on the given data.
     #[tracing::instrument(level = "trace", skip(self))]
     fn update_snapshot_state(&mut self, update: SnapshotUpdate) {
-        if let SnapshotUpdate::SnapshotComplete(index) = update {
-            self.snapshot_index = index
+        if let SnapshotUpdate::SnapshotComplete(log_id) = update {
+            self.snapshot_last_included = log_id
         }
         // If snapshot state is anything other than streaming, then drop it.
         if let Some(state @ SnapshotState::Streaming { .. }) = self.snapshot_state.take() {
@@ -425,13 +426,13 @@ impl<D: AppData, R: AppDataResponse, N: RaftNetwork<D>, S: RaftStorage<D, R>> Ra
         }
         let SnapshotPolicy::LogsSinceLast(threshold) = &self.config.snapshot_policy;
         // Check to ensure we have actual entries for compaction.
-        if self.last_applied == 0 || self.last_applied < self.snapshot_index {
+        if self.last_applied == 0 || self.last_applied < self.snapshot_last_included.index {
             return;
         }
 
         if !force {
             // If we are below the threshold, then there is nothing to do.
-            if self.last_applied < self.snapshot_index + *threshold {
+            if self.last_applied < self.snapshot_last_included.index + *threshold {
                 return;
             }
         }
@@ -452,7 +453,7 @@ impl<D: AppData, R: AppDataResponse, N: RaftNetwork<D>, S: RaftStorage<D, R>> Ra
                 match res {
                     Ok(res) => match res {
                         Ok(snapshot) => {
-                            let _ = tx_compaction.try_send(SnapshotUpdate::SnapshotComplete(snapshot.included.index));
+                            let _ = tx_compaction.try_send(SnapshotUpdate::SnapshotComplete(snapshot.included));
                             let _ = chan_tx.send(snapshot.included.index); // This will always succeed.
                         }
                         Err(err) => {
@@ -549,7 +550,7 @@ pub(self) enum SnapshotState<S> {
 #[derive(Debug)]
 pub(self) enum SnapshotUpdate {
     /// Snapshot creation has finished successfully and covers the given index.
-    SnapshotComplete(u64),
+    SnapshotComplete(LogId),
     /// Snapshot creation failed.
     SnapshotFailed,
 }