Update reconciliation.md

design/reconciliation.md

@@ -1,27 +1,26 @@
 # Cluster Membership Reconciliation
 
-## Recovery
+## Reconciliation
 
 Given a desired size S, we have two membership states:
 - running pods P in k8s cluster
 - membership M in controller knowledge
 
-Recovery is the process to make these two states consistent.  Assuming “len(M) = S” here.
+Reconciliation is the process to make these two states consistent with the desired size S.
 
 For each reconciling cycle, we get P from k8s API. Comparing M and P, we have the following steps:
 
 1. Remove all pods from set P that does not belong to set M
 2. P’ consist of remaining pods of P
-3. If P’ = M, the current state matches the membership state. END.
+3. If P’ = M, the current state matches the membership state. GOTO Resize.
 4. If len(P’) < len(M)/2 + 1, quorum lost. Go to recovery process (TODO).
-5. Add one missing member. END.
+5. Remove one member that in M but does not in P's. GOTO Resize. 
 
-## Resize
-
-Before resizing an etcd cluster, we need to ensure the running Pods set matches the membership knowledge. Or we need to do recovery first.
+### Resize
 
 Given a desired size S and membership size M:
 
-1. If S = M, then END.
-2. If S > M, add one member. END.
-3. If S < M, remove one member. END
+1. If P' != M, then END.
+2. If S = M, then END.
+3. If S > M, add one member. END.
+4. If S < M, remove one member. END