support skip bcast commit at run time (#115)

Only users know whether a message needs to be commit eagerly. So provide a way
to configure the feature at run time.

src/raft.rs

@@ -389,6 +389,12 @@ impl<T: Storage> Raft<T> {
         self.randomized_election_timeout
     }
 
+    /// Set whether skip broadcast empty commit messages at runtime.
+    #[inline]
+    pub fn skip_bcast_commit(&mut self, skip: bool) {
+        self.skip_bcast_commit = skip;
+    }
+
     // send persists state to stable storage and then sends to its mailbox.
     fn send(&mut self, mut m: Message) {
         m.set_from(self.id);

src/raw_node.rs

@@ -474,6 +474,12 @@ impl<T: Storage> RawNode<T> {
     pub fn mut_store(&mut self) -> &mut T {
         self.raft.mut_store()
     }
+
+    /// Set whether skip broadcast empty commit messages at runtime.
+    #[inline]
+    pub fn skip_bcast_commit(&mut self, skip: bool) {
+        self.raft.skip_bcast_commit(skip)
+    }
 }
 
 #[cfg(test)]

tests/cases/test_raw_node.rs

@@ -497,13 +497,22 @@ fn test_skip_bcast_commit() {
     assert_eq!(nt.peers[&2].raft_log.committed, 2);
     assert_eq!(nt.peers[&3].raft_log.committed, 2);
 
-    // Later proposal should commit former proposal.
+    // The feature should be able to be adjusted at run time.
+    nt.peers.get_mut(&1).unwrap().skip_bcast_commit(false);
     nt.send(vec![msg.clone()]);
-    nt.send(vec![msg]);
-    assert_eq!(nt.peers[&1].raft_log.committed, 4);
+    assert_eq!(nt.peers[&1].raft_log.committed, 3);
     assert_eq!(nt.peers[&2].raft_log.committed, 3);
     assert_eq!(nt.peers[&3].raft_log.committed, 3);
 
+    nt.peers.get_mut(&1).unwrap().skip_bcast_commit(true);
+
+    // Later proposal should commit former proposal.
+    nt.send(vec![msg.clone()]);
+    nt.send(vec![msg]);
+    assert_eq!(nt.peers[&1].raft_log.committed, 5);
+    assert_eq!(nt.peers[&2].raft_log.committed, 4);
+    assert_eq!(nt.peers[&3].raft_log.committed, 4);
+
     // When committing conf change, leader should always bcast commit.
     let mut cc_entry = Entry::new();
     cc_entry.set_entry_type(EntryType::EntryConfChange);
@@ -517,7 +526,7 @@ fn test_skip_bcast_commit() {
     assert!(nt.peers[&2].should_bcast_commit());
     assert!(nt.peers[&3].should_bcast_commit());
 
-    assert_eq!(nt.peers[&1].raft_log.committed, 5);
-    assert_eq!(nt.peers[&2].raft_log.committed, 5);
-    assert_eq!(nt.peers[&3].raft_log.committed, 5);
+    assert_eq!(nt.peers[&1].raft_log.committed, 6);
+    assert_eq!(nt.peers[&2].raft_log.committed, 6);
+    assert_eq!(nt.peers[&3].raft_log.committed, 6);
 }