Flavio Junqueira commented on ZOOKEEPER-2982:

I think I know what's going on. It is correct that {{connectOne}} invokes 
{{recreateSocketAddresses}}, but that invocation won't happen in the case that 
the server receives a connection request rather than starting the connection. 
In fact, servers with larger ids are always supposed to start the connections.

I think the patch proposed here of invoking {{recreateSocketAddresses}} in 
{{findLeader}} in the learner class makes sense to compensate for 
{{recreateSocketAddresses}} not being invoked during leader election. Any other 
insight or anything I'm missing?

> Re-try DNS hostname -> IP resolution
> ------------------------------------
>                 Key: ZOOKEEPER-2982
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2982
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.5.0, 3.5.1, 3.5.3
>            Reporter: Eron Wright 
>            Priority: Blocker
>             Fix For: 3.5.4, 3.6.0
>         Attachments: 3.5.3-beta.zip, fixed.log
> ZOOKEEPER-1506 fixed a DNS resolution issue in 3.4.  Some portions of the fix 
> haven't yet been ported to 3.5.
> To recap the outstanding problem in 3.5, if a given ZK server is started 
> before all peer addresses are resolvable, that server may cache a negative 
> lookup result and forever fail to resolve the address.    For example, 
> deploying ZK 3.5 to Kubernetes using a StatefulSet plus a Service (headless) 
> may fail because the DNS records are created lazily.
> {code}
> 2018-02-18 09:11:22,583 [myid:0] - WARN  
> [QuorumPeer[myid=0](plain=/0:0:0:0:0:0:0:0:2181)(secure=disabled):Follower@95]
>  - Exception when following the leader
> java.net.UnknownHostException: zk-2.zk.default.svc.cluster.local
>         at 
> java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184)
>         at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
>         at java.net.Socket.connect(Socket.java:589)
>         at 
> org.apache.zookeeper.server.quorum.Learner.sockConnect(Learner.java:227)
>         at 
> org.apache.zookeeper.server.quorum.Learner.connectToLeader(Learner.java:256)
>         at 
> org.apache.zookeeper.server.quorum.Follower.followLeader(Follower.java:76)
>         at 
> org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:1133)
> {code}
> In the above example, the address `zk-2.zk.default.svc.cluster.local` was not 
> resolvable when the server started, but became resolvable shortly thereafter. 
>    The server should eventually succeed but doesn't.

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