[ZOOKEEPER-1734] Zookeeper fails to connect if one zookeeper host is down on EC2 when using elastic IP (UnknownHostException)

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.4.5
• Component/s: java client

Environment

Amazon EC2. Linux.

• Assignee: Unassigned
• Reporter: Andy Grove
• Created: 22/Jul/13 20:28
• Updated: 15/Jul/14 17:22

Description

We use Amazon Elastic IP for zookeeper hosts so that the zookeeper hosts have the same IP address after a restart.

The issue is, if one host is down then we cannot connect to the other hosts.

Here is an example connect string:

"ec2-1-2-3-4.compute-1.amazonaws.com, ec2-4-3-2-1.compute-1.amazonaws.com, ec2-5-5-5-5.compute-1.amazonaws.com"

If all three hosts are up, we can connect. If one host is down, then we cannot create a Zookeeper instance due to an UnknownHost exception, even though the other servers in the connect string are valid.

java.net.UnknownHostException: ec2-5-5-5-5.compute-1.amazonaws.com
at java.net.InetAddress.getAllByName0(InetAddress.java:1243)
at java.net.InetAddress.getAllByName(InetAddress.java:1155)
at java.net.InetAddress.getAllByName(InetAddress.java:1091)
at org.apache.zookeeper.client.StaticHostProvider.<init>(StaticHostProvider.java:60)
at org.apache.zookeeper.ZooKeeper.<init>(ZooKeeper.java:445)

Issue Links

• is related to: ZOOKEEPER-1576 Zookeeper cluster - failed to connect to cluster if one of the provided IPs causes java.net.UnknownHostException