raft: immediately commit and apply first entry on single-node clusters

src/raft/node.rs

@@ -320,6 +320,7 @@ impl RawNode<Candidate> {
  // We do this prior to the heartbeat, to avoid a wasted replication
  // roundtrip if the heartbeat response indicates the peer is behind.
  node.propose(None)?;
+ node.maybe_commit_and_apply()?;
  node.heartbeat()?;
 
  Ok(node)
@@ -1505,6 +1506,8 @@ mod tests {
  };
  self.nodes.insert(id, Node::new(id, peers, log, state, node_tx, opts)?);
 
+ while applied_rx.try_recv().is_ok() {} // drain first apply
+
  self.nodes_rx.insert(id, node_rx);
  self.nodes_pending.insert(id, Vec::new());
  self.applied_rx.insert(id, applied_rx);

src/raft/testscripts/node/request_leader_single

@@ -2,7 +2,7 @@
 
 cluster nodes=1
 ---
-n1@1 leader last=1@1 commit=0@0 apply=0 progress={}
+n1@1 leader last=1@1 commit=1@1 apply=1 progress={}
 
 # An initial get on the leader yields None.
 get 1 foo
@@ -19,7 +19,6 @@ stabilize heartbeat=true
 c1@1 → n1 ClientRequest id=0x02 write 0x0103666f6f03626172
 n1@1 append 2@1 put foo=bar
 n1@1 commit 2@1
-n1@1 apply 1@1 None
 n1@1 apply 2@1 put foo=bar
 n1@1 → c1 ClientResponse id=0x02 write 0x0102
 c1@1 put foo=bar ⇒ 2

src/raft/testscripts/node/request_status_single

@@ -2,7 +2,7 @@
 
 cluster nodes=1
 ---
-n1@1 leader last=1@1 commit=0@0 apply=0 progress={}
+n1@1 leader last=1@1 commit=1@1 apply=1 progress={}
 
 # Perform a write.
 (put 1 foo=bar)