Issue
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The Jenkins instance hangs when installing plugins
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An UnknownHostException occurs on startup:
2016-02-07 02:45:07.730+0000 [id=73] WARNING javax.jmdns.impl.HostInfo#newHostInfo: Could not intialize the host network interface on nullbecause of an error: <my-hostname>: <my-hostname>: unknown errorjava.net.UnknownHostException: <my-hostname>: <my-hostname>: unknown error
at java.net.InetAddress.getLocalHost(InetAddress.java:1484)
at javax.jmdns.impl.HostInfo.newHostInfo(HostInfo.java:75)
at javax.jmdns.impl.JmDNSImpl.<init>(JmDNSImpl.java:407)
at javax.jmdns.JmDNS.create(JmDNS.java:60)
at hudson.DNSMultiCast$1.call(DNSMultiCast.java:32)
at jenkins.util.ContextResettingExecutorService$2.call(ContextResettingExecutorService.java:46)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.UnknownHostException: <my-hostname>: unknown error
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:907)
at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1302)
at java.net.InetAddress.getLocalHost(InetAddress.java:1479)
... 9 more
Environment
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CloudBees Jenkins Enterprise (CJE)
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CloudBees Jenkins Enterprise - Managed controller (CJE-MM)
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CloudBees Jenkins Enterprise - Operations center (CJE-OC)
Resolution
1. Disable DNS Discovery
This could be due to the Auto-discovering of Jenkins with DNS Multicast. If you are not using this functionality you can disable it by adding the following properties on startup and restart your instance:
-Dhudson.DNSMultiCast.disabled=true -Dhudson.udp=-1
If Jenkins is running on Apache Tomcat, you can add the following property to catalina.properties:
hudson.DNSMultiCast.disabled=true hudson.udp=-1
2. Troubleshoot your Hosts/DNS configuration
This could be a misconfiguration of your hostname or your DNS.
Use ping, nc, or telnet to check that the host can be resolved:
$ ping my-hostname PING my-hostname (...): 56 data bytes ... $ nc -z my-hostname port Connection to my-hostname port port succeeded! $ telnet my-hostname port Trying my-hostname... Connected to my-hostname. Escape character is '^]'.
If you are not using a DNS, check that the <hostname> is defined in /etc/hosts:
[...] 127.0.0.1 localhost my-hostname [...]
If you are using a DNS, try to telnet on DNS port to check that the port is open (default port is 53):
$ telnet my-hostname dns-port Trying 127.0.0.1... Connected to my-hostname. Escape character is '^]'.
# Query a hostname for the default server nslookup my-hostname # Query a hostname for a different server nslookup my-hostname my-dns-server # List IP address(es) associated with a hostname/domain: host -l my-hostname # Query a hostname for the default server dig my-hostname # Query a hostname for the different server dig @my-server my-hostname