It looks like zkclient bubbling up the zookeeper error even if one of the hosts failed to resolve
org.I0Itec.zkclient.exception.ZkException: Unable to connect to {quorum}
at org.I0Itec.zkclient.ZkConnection.connect(ZkConnection.java:72)
at org.I0Itec.zkclient.ZkClient.reconnect(ZkClient.java:1289)
at org.I0Itec.zkclient.ZkClient.processStateChanged(ZkClient.java:721)
at org.I0Itec.zkclient.ZkClient.process(ZkClient.java:632)
at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:530)
at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:505)
Caused by: java.net.UnknownHostException: {hostname} : unknown error
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:928)
at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1323)
at java.net.InetAddress.getAllByName0(InetAddress.java:1276)
at java.net.InetAddress.getAllByName(InetAddress.java:1192)
at java.net.InetAddress.getAllByName(InetAddress.java:1126)
at org.apache.zookeeper.client.StaticHostProvider.(StaticHostProvider.java:61)
at org.apache.zookeeper.ZooKeeper.(ZooKeeper.java:445)
at org.apache.zookeeper.ZooKeeper.(ZooKeeper.java:380)
at org.I0Itec.zkclient.ZkConnection.connect(ZkConnection.java:70)
It did get fixed in zookeeper 3.5.0 https://issues.apache.org/jira/browse/ZOOKEEPER-1576 but 3.5.0 is still in beta. I am happy to provide a similar fix in zkClient until we upgrade to 3.5.0. Let me know if it can be acceptable fix.
harshach
commented
6 years ago 
jzillmann
commented
6 years ago
It looks like zkclient bubbling up the zookeeper error even if one of the hosts failed to resolve org.I0Itec.zkclient.exception.ZkException: Unable to connect to {quorum} at org.I0Itec.zkclient.ZkConnection.connect(ZkConnection.java:72) at org.I0Itec.zkclient.ZkClient.reconnect(ZkClient.java:1289) at org.I0Itec.zkclient.ZkClient.processStateChanged(ZkClient.java:721) at org.I0Itec.zkclient.ZkClient.process(ZkClient.java:632) at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:530) at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:505) Caused by: java.net.UnknownHostException: {hostname} : unknown error at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method) at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:928) at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1323) at java.net.InetAddress.getAllByName0(InetAddress.java:1276) at java.net.InetAddress.getAllByName(InetAddress.java:1192) at java.net.InetAddress.getAllByName(InetAddress.java:1126) at org.apache.zookeeper.client.StaticHostProvider.(StaticHostProvider.java:61)
at org.apache.zookeeper.ZooKeeper.(ZooKeeper.java:445)
at org.apache.zookeeper.ZooKeeper.(ZooKeeper.java:380)
at org.I0Itec.zkclient.ZkConnection.connect(ZkConnection.java:70)
It did get fixed in zookeeper 3.5.0 https://issues.apache.org/jira/browse/ZOOKEEPER-1576 but 3.5.0 is still in beta. I am happy to provide a similar fix in zkClient until we upgrade to 3.5.0. Let me know if it can be acceptable fix.