chore(meta): remove unused code

Author: drmingdrmer

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

@@ -1046,7 +1046,7 @@ impl StateMachine {
         sm_nodes.range_values(..)
     }
 
-    /// Expire an `SeqV` and returns:
+    /// Expire an `SeqV` and returns the value discarded by expiration and the unexpired value:
     /// - `(Some, None)` if it expires.
     /// - `(None, Some)` if it does not.
     /// - `(None, None)` if the input is None.
@@ -1064,32 +1064,6 @@ impl StateMachine {
             (None, None)
         }
     }
-
-    pub fn unexpired<V: Debug>(seq_value: SeqV<V>, log_time_ms: u64) -> Option<SeqV<V>> {
-        // Caveat: The cleanup must be consistent across raft nodes:
-        //         A conditional update, e.g. an upsert_kv() with MatchSeq::Eq(some_value),
-        //         must be applied with the same timestamp on every raft node.
-        //         Otherwise: node-1 could have applied a log with a ts that is smaller than value.expire_at,
-        //         while node-2 may fail to apply the same log if it use a greater ts > value.expire_at.
-        //
-        // Thus:
-        //
-        // 1. A raft log must have a field ts assigned by the leader. When applying, use this ts to
-        //    check against expire_at to decide whether to purge it.
-        // 2. A GET operation must not purge any expired entry. Since a GET is only applied to a node itself.
-        // 3. The background task can only be triggered by the raft leader, by submit a "clean expired" log.
-
-        // TODO(xp): background task to clean expired
-        // TODO(xp): maybe it needs a expiration queue for efficient cleaning up.
-
-        debug!("seq_value: {:?} log_time_ms: {}", seq_value, log_time_ms);
-
-        if seq_value.get_expire_at() < log_time_ms {
-            None
-        } else {
-            Some(seq_value)
-        }
-    }
 }
 
 /// Key space support

src/meta/raft-store/src/state_machine/sm_kv_api_impl.rs

@@ -75,13 +75,10 @@ impl KVApi for StateMachine {
         // TODO(xp) refine get(): a &str is enough for key
         let sv = self.kvs().get(&key.to_string())?;
         debug!("get_kv sv:{:?}", sv);
-        let seq_v = match sv {
-            None => return Ok(None),
-            Some(sv) => sv,
-        };
 
         let local_now_ms = SeqV::<()>::now_ms();
-        Ok(Self::unexpired(seq_v, local_now_ms))
+        let (_expired, res) = Self::expire_seq_v(sv, local_now_ms);
+        Ok(res)
     }
 
     async fn mget_kv(&self, keys: &[String]) -> Result<MGetKVReply, KVAppError> {
@@ -111,7 +108,7 @@ impl KVApi for StateMachine {
         let local_now_ms = SeqV::<()>::now_ms();
 
         // Convert expired to None
-        let x = x.map(|(k, v)| (k, Self::unexpired(v, local_now_ms)));
+        let x = x.map(|(k, v)| (k, Self::expire_seq_v(Some(v), local_now_ms)[1]));
         // Remove None
         let x = x.filter(|(_k, v)| v.is_some());
         // Extract from an Option

src/meta/service/tests/it/tests/meta_node.rs

@@ -35,7 +35,6 @@ pub(crate) async fn start_meta_node_cluster(
     voters: BTreeSet<NodeId>,
     non_voters: BTreeSet<NodeId>,
 ) -> anyhow::Result<(u64, Vec<MetaSrvTestContext>)> {
-    // TODO(xp): use setup_cluster if possible in tests. Get rid of boilerplate snippets.
     // leader is always node-0
     assert!(voters.contains(&0));
     assert!(!non_voters.contains(&0));