Jenkins log shows lots of 'javax.jmdns.impl.DNSIncoming' SEVERE Messages

Article ID:360021422131
2 minute readKnowledge base

Issue

  • The Jenkins logs are polluted with SEVERE messages like the following:

SEVERE: Extended label are not currently supported.
Dec 17, 2018 4:23:36 PM javax.jmdns.impl.DNSIncoming$MessageInputStream readName
SEVERE: Extended label are not currently supported.
Dec 17, 2018 4:23:36 PM javax.jmdns.impl.DNSIncoming$MessageInputStream readName
SEVERE: bad domain name: possible circular name detected. Bad offset: 0xffffffff at 0x69
Dec 17, 2018 4:23:36 PM javax.jmdns.impl.constants.DNSRecordType typeForIndex
SEVERE: Could not find record type for index: -1
Dec 17, 2018 4:23:36 PM javax.jmdns.impl.DNSIncoming readQuestion
SEVERE: Could not find record type: dns[query,192.168.123.123:4321, length=107, id=0x0]
   0: 0000000000010000 0001000043746561 6d732d746573746e 65776d6173746572     ........ ....Ctea ms-testn ewmaster
  20: 2d302d7465616d73 2d746573746e6577 6d61737465722d64 656661756c742d73     -0-teams -testnew controller-d efault-s
  40: 76632d636c757374 65722d6c6f63616c 056c6f63616c0000 ff0001c00c000100     vc-clust er-local .local.. ........
  60: 0100000e100004c0 a8c881
  [...]

Environment

Explanation

These logs are generated by JmDNS, a DNS multicast library that Jenkins uses for its auto-discovery feature.

At the moment of writing this article:

  • Jenkins uses an old fork of that library jenkinsci/jmdns

  • the auto-discovery feature is enabled by default

These SEVERE messages appear when Jenkins receives DNS Messages of a type that is not supported. Whether an instance is impacted or not strongly depends on the environment where it runs.

Resolution

There is a known improvement issue JENKINS-50816 to disable the DNS Multicast functionality by default or even detach it from Jenkins core. Until then, the workaround is to disable the functionality by adding the system property -Dhudson.DNSMultiCast.disabled=true on Jenkins startup - see How to add Java arguments to Jenkins? to understand how to do this. A restart is required to apply the changes.

This article is part of our Knowledge Base and is provided for guidance-based purposes only. The solutions or workarounds described here are not officially supported by CloudBees and may not be applicable in all environments. Use at your own discretion, and test changes in a safe environment before applying them to production systems.