some code reading notes

safekeeper/src/safekeeper.rs

@@ -858,7 +858,7 @@ where
     ///
     /// Note: it is assumed that 'WAL we have is from the right term' check has
     /// already been done outside.
-    async fn update_commit_lsn(&mut self, mut candidate: Lsn) -> Result<()> {
+    async fn update_commit_lsn(&mut self, mut candidate: Lsn) -> Result<()> { // updates to inmem.commit_lsn go through here
         // Both peers and walproposer communicate this value, we might already
         // have a fresher (higher) version.
         candidate = max(candidate, self.state.inmem.commit_lsn);

safekeeper/src/send_wal.rs

@@ -468,7 +468,7 @@ impl SafekeeperPostgresHandler {
         &mut self,
         pgb: &mut PostgresBackend<IO>,
         start_pos: Lsn,
-        term: Option<Term>,
+        term: Option<Term>, // none for pageserver
         tli: WalResidentTimeline,
     ) -> Result<(), CopyStreamHandlerEnd> {
         let appname = self.appname.clone();

safekeeper/src/state.rs

@@ -227,7 +227,7 @@ where
         }
 
         // keep in memory values up to date
-        self.inmem.commit_lsn = s.commit_lsn;
+        self.inmem.commit_lsn = s.commit_lsn; // and here?
         self.inmem.backup_lsn = s.backup_lsn;
         self.inmem.peer_horizon_lsn = s.peer_horizon_lsn;
         self.inmem.remote_consistent_lsn = s.remote_consistent_lsn;

safekeeper/src/timeline.rs

@@ -124,6 +124,7 @@ impl Drop for WriteGuardSharedState<'_> {
             }
         });
 
+        // this here wakes `send_wal`
         let _ = self.tli.commit_lsn_watch_tx.send_if_modified(|old| {
             if *old != commit_lsn {
                 *old = commit_lsn;