From 191c5e56419ef7318ae99e25530d66e9e2ece453 Mon Sep 17 00:00:00 2001
From: Arthur Petukhovsky <petuhovskiy@yandex.ru>
Date: Tue, 12 Apr 2022 11:47:08 +0000
Subject: [PATCH] Create ElectedProposerInfo struct

---
 walkeeper/src/safekeeper.rs | 50 ++++++++++++++++++++++++++-----------
 1 file changed, 35 insertions(+), 15 deletions(-)

diff --git a/walkeeper/src/safekeeper.rs b/walkeeper/src/safekeeper.rs
index 22a8481e45..070f6f29cc 100644
--- a/walkeeper/src/safekeeper.rs
+++ b/walkeeper/src/safekeeper.rs
@@ -203,14 +203,33 @@ pub struct SafeKeeperState {
 }
 
 #[derive(Debug, Clone)]
-// In memory safekeeper state. Fields mirror ones in `SafeKeeperState`; values
-// are not flushed yet.
+/// In memory safekeeper state. Fields mirror ones in `SafeKeeperState`; values
+/// are not flushed yet.
 pub struct SafekeeperMemState {
     pub commit_lsn: Lsn,
     pub s3_wal_lsn: Lsn, // TODO: keep only persistent version
     pub peer_horizon_lsn: Lsn,
     pub remote_consistent_lsn: Lsn,
-    pub proposer_uuid: PgUuid,
+}
+
+#[derive(Debug, Clone)]
+/// In memory state for last elected proposer.
+struct ElectedProposerInfo {
+    /// UUID of a elected proposer
+    proposer_uuid: PgUuid,
+
+    /// LSN since the proposer safekeeper currently talking to appends WAL;
+    /// determines epoch switch point.
+    epoch_start_lsn: Lsn,
+}
+
+impl ElectedProposerInfo {
+    pub fn empty() -> Self {
+        Self {
+            proposer_uuid: [0; 16],
+            epoch_start_lsn: Lsn(0),
+        }
+    }
 }
 
 impl SafeKeeperState {
@@ -493,18 +512,20 @@ impl SafeKeeperMetrics {
 /// SafeKeeper which consumes events (messages from compute) and provides
 /// replies.
 pub struct SafeKeeper<CTRL: control_file::Storage, WAL: wal_storage::Storage> {
-    // Cached metrics so we don't have to recompute labels on each update.
+    /// Cached metrics so we don't have to recompute labels on each update.
     metrics: SafeKeeperMetrics,
 
     /// Maximum commit_lsn between all nodes, can be ahead of local flush_lsn.
     pub global_commit_lsn: Lsn,
-    /// LSN since the proposer safekeeper currently talking to appends WAL;
-    /// determines epoch switch point.
-    epoch_start_lsn: Lsn,
+    /// In-memory info about the elected proposer.
+    elected: ElectedProposerInfo,
 
-    pub inmem: SafekeeperMemState, // in memory part
-    pub state: CTRL,               // persistent state storage
+    /// In-memory consensus state, not yet persisted to disk.
+    pub inmem: SafekeeperMemState,
+    /// SafeKeeperState persisted to disk and methods for update.
+    pub state: CTRL,
 
+    /// WAL storage with write functions.
     pub wal_store: WAL,
 }
 
@@ -529,13 +550,12 @@ where
         Ok(SafeKeeper {
             metrics: SafeKeeperMetrics::new(state.tenant_id, ztli),
             global_commit_lsn: state.commit_lsn,
-            epoch_start_lsn: Lsn(0),
+            elected: ElectedProposerInfo::empty(),
             inmem: SafekeeperMemState {
                 commit_lsn: state.commit_lsn,
                 s3_wal_lsn: state.s3_wal_lsn,
                 peer_horizon_lsn: state.peer_horizon_lsn,
                 remote_consistent_lsn: state.remote_consistent_lsn,
-                proposer_uuid: state.proposer_uuid,
             },
             state,
             wal_store,
@@ -724,7 +744,7 @@ where
         // Also note that commit_lsn can reach epoch_start_lsn earlier
         // that we receive new epoch_start_lsn, and we still need to sync
         // control file in this case.
-        if commit_lsn == self.epoch_start_lsn && self.state.commit_lsn != commit_lsn {
+        if commit_lsn == self.elected.epoch_start_lsn && self.state.commit_lsn != commit_lsn {
             self.persist_control_file()?;
         }
 
@@ -744,7 +764,7 @@ where
 
         state.commit_lsn = self.inmem.commit_lsn;
         state.peer_horizon_lsn = self.inmem.peer_horizon_lsn;
-        state.proposer_uuid = self.inmem.proposer_uuid;
+        state.proposer_uuid = self.elected.proposer_uuid;
         self.state.persist(&state)
     }
 
@@ -768,8 +788,8 @@ where
         // Now we know that we are in the same term as the proposer,
         // processing the message.
 
-        self.epoch_start_lsn = msg.h.epoch_start_lsn;
-        self.inmem.proposer_uuid = msg.h.proposer_uuid;
+        self.elected.epoch_start_lsn = msg.h.epoch_start_lsn;
+        self.elected.proposer_uuid = msg.h.proposer_uuid;
 
         // do the job
         if !msg.wal_data.is_empty() {