[ZOOKEEPER-1789] 3.4.x observer causes NPE on 3.5.0 (trunk) participants

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 3.5.0
• Fix Version/s: 3.5.0
• Hadoop Flags: Reviewed
• Assignee: Alexander Shraer
• Reporter: Raúl Gutiérrez Segalés
• Created: 10/Oct/13 23:10
• Updated: 24/Jul/14 11:22
• Resolved: 23/Jul/14 17:36

Description

(assigning to Alex because this was introduced by ZOOKEEPER-107, but will upload a patch as well.)

I have a 5 participants cluster running what will be 3.5.0 (i.e.: trunk as of today) and an observer running 3.4 (trunk from 3.4 branch). When the observer tries to establish a connection to the participants I get:

Thread Thread[10.40.78.121:3888,5,main] died java.lang.NullPointerException at org.apache.zookeeper.server.quorum.QuorumCnxManager.receiveConnection(QuorumCnxManager.java:240)
        at org.apache.zookeeper.server.quorum.QuorumCnxManager$Listener.run(QuorumCnxManager.java:552)

Looking at QuorumCnxManager.java:240:

            if (protocolVersion >= 0) { // this is a server id and not a protocol version                                                             
               sid = protocolVersion;
                electionAddr = self.getVotingView().get(sid).electionAddr;
            } else {

and self.getVotingView().get(sid) will be null for Observers. So this block should cover that case.