fix andreev-io#13, Add Abandoned type to TransitionState enum

little_raft/src/replica.rs

@@ -1,7 +1,7 @@
 use crate::{
     cluster::Cluster,
     message::{LogEntry, Message},
-    state_machine::{StateMachine, StateMachineTransition, TransitionState},
+    state_machine::{StateMachine, StateMachineTransition, TransitionState, TransitionAbandonedReason},
     timer::Timer,
 };
 use crossbeam_channel::{Receiver, Select};
@@ -377,6 +377,11 @@ where
                 let mut state_machine = self.state_machine.lock().unwrap();
                 state_machine
                     .register_transition_state(transition.get_id(), TransitionState::Queued);
+            } else {
+                let mut state_machine = self.state_machine.lock().unwrap();
+                state_machine
+                    .register_transition_state(
+                        transition.get_id(), TransitionState::Abandoned(TransitionAbandonedReason::NotLeader));
             }
         }
     }

little_raft/src/state_machine.rs

@@ -16,6 +16,15 @@ pub enum TransitionState {
     /// Applied transitions have been replicated across the cluster and have
     /// been applied to the local state machine.
     Applied,
+
+    /// Abandoned transitions have been ignored by the replica.
+    Abandoned(TransitionAbandonedReason),
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum TransitionAbandonedReason {
+    // NotLeader transitions have been abandoned because the replica is not the cluster leadedr.
+    NotLeader,
 }
 
 /// StateMachineTransition describes a user-defined transition that can be