[GitHub] [zookeeper] enixon commented on a change in pull request #958: ZOOKEEPER-1523: Better logging during instance loading/syncing

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enixon commented on a change in pull request #958: ZOOKEEPER-1523: Better logging during instance loading/syncing
URL: https://github.com/apache/zookeeper/pull/958#discussion_r299635734
 
 

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 File path: zookeeper-server/src/main/java/org/apache/zookeeper/server/quorum/QuorumPeer.java
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 @@ -416,6 +416,22 @@ public void checkAddressDuplicate(QuorumServer s) throws BadArgumentsException {
         LOOKING, FOLLOWING, LEADING, OBSERVING;
     }
 
+    /**
+     * (Used for monitoring) When peer is in non-LOOKING phase, this shows the
+     * current phase of Zab protocol that peer is running.
+     */
+    public enum ZabState {
+        NONE, DISCOVERY, SYNCHRONIZATION, BROADCAST;
 
 Review comment:
   Most of the Zab literature talks about a three phases of Zab:
   1. discovery
   2. synchronization
   3. broadcast
   
   Left implicit is the degenerate phase:
   0. maybe in leader election
   
   (see https://distributedalgorithm.wordpress.com/2015/06/20/architecture-of-zab-zookeeper-atomic-broadcast-protocol/ or http://www.tcs.hut.fi/Studies/T-79.5001/reports/2012-deSouzaMedeiros.pdf)
   
   I'd say that we do want a concept of the degenerate state. NONE is a reasonable thing to call it, as is ELECTION to my mind. I'll modify the comment to remove the mention of "nonlooking".

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