Failed to connect to http://jenkins.build-env.svc.cluster.local:8080/tcpSlaveAgentListener/: jenkins.build-env.svc.cluster.local

[WANG, YAN-HONG]

Hello,

My environment:

Jenkins: 2.73.1

Jenkins plugin (kubernetes: 1.0).

Kuberntes Server: v1.7.7 ( One master and one minion)

Platform: Ubuntu 16.04 (in Synnefo cluster environment)

When I execute pipeline job with kubernetes plugin in Jenkins environment.

The slave-jksnf-q6dlr is stay in "offline" state.

$ ​kubectl --namespace=build-env logs slave-jksnf-q6dlr jnlp

Warning: JnlpProtocol3 is disabled by default, use JNLP_PROTOCOL_OPTS to alter the behavior
Warning: SECRET is defined twice in command-line arguments and the environment variable
Warning: AGENT_NAME is defined twice in command-line arguments and the environment variable
Oct 05, 2017 1:29:32 PM hudson.remoting.jnlp.Main createEngine
INFO: Setting up slave: slave-jksnf-q6dlr
Oct 05, 2017 1:29:32 PM hudson.remoting.jnlp.Main$CuiListener <init>
INFO: Jenkins agent is running in headless mode.
Oct 05, 2017 1:29:32 PM hudson.remoting.Engine startEngine
WARNING: No Working Directory. Using the legacy JAR Cache location: /home/jenkins/.jenkins/cache/jars
Oct 05, 2017 1:29:32 PM hudson.remoting.jnlp.Main$CuiListener status
INFO: Locating server among [http://jenkins.build-env.svc.cluster.local:8080/]
Oct 05, 2017 1:29:37 PM hudson.remoting.jnlp.Main$CuiListener error
SEVERE: Failed to connect to http://jenkins.build-env.svc.cluster.local:8080/tcpSlaveAgentListener/: jenkins.build-env.svc.cluster.local
java.io.IOException: Failed to connect to http://jenkins.build-env.svc.cluster.local:8080/tcpSlaveAgentListener/: jenkins.build-env.svc.cluster.local
    at org.jenkinsci.remoting.engine.JnlpAgentEndpointResolver.resolve(JnlpAgentEndpointResolver.java:161)
    at hudson.remoting.Engine.innerRun(Engine.java:495)
    at hudson.remoting.Engine.run(Engine.java:447)
Caused by: java.net.UnknownHostException: jenkins.build-env.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 sun.net.NetworkClient.doConnect(NetworkClient.java:175)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:463)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:558)
    at sun.net.www.http.HttpClient.<init>(HttpClient.java:242)
    at sun.net.www.http.HttpClient.New(HttpClient.java:339)
    at sun.net.www.http.HttpClient.New(HttpClient.java:357)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1202)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1138)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1032)
    at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:966)
    at org.jenkinsci.remoting.engine.JnlpAgentEndpointResolver.resolve(JnlpAgentEndpointResolver.java:158)
    ... 2 more

It looks seem DNS can't solve name issue? or?

But, in minikube environment, there is no this problem...

Thanks very much.

Hong

[Carlos Sanchez]

you are correct your kubernetes DNS can't resolve the name, assuming you have a service jenkins in the build-env namespace

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[YAN-HONG WANG]

Hello Carlos,

Thanks for reply again.
And I obviously have jenkins service expose in namespace "build-env".

$ kubectl --namespace=build-env get service
NAME      TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)                                         AGE
jenkins   NodePort   10.98.101.107   <none>        8080:30808/TCP,8443:30443/TCP,50000:30500/TCP   15h

In my working environment, there are seems some DNS issue.
So for example, I use this short workaround to deploy in my jenkins.yaml.
and then "Test Connection" can "Connection successful"

------------------------------------------------------------------------------------
hostAliases:
- ip: "10.96.0.1"
  hostnames:
  - "kubernetes.default.svc.cluster.local"
------------------------------------------------------------------------------------

So in podTemplate, is there any similar syntax like above?
And that could solve jenkins.build-env.svc.cluster.local naming issue in container JNLP of slave?

But, if the service ip address of Jenkins is not static, that is still a problem in my environment...
Thanks.

Hong

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[YAN-HONG WANG]

Hello Carlos,

In containerTemplate, I define one container "worker".
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
$ kubectl --namespace=build-env exec -it slave-0cnkz-gv0bg --container=worker cat /etc/resolv.conf
nameserver 10.96.0.10
search build-env.svc.cluster.local svc.cluster.local cluster.local
options ndots:5

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
FQDN
$ kubectl --namespace=build-env exec -it slave-0cnkz-gv0bg --container=worker nslookup jenkins.build-env.svc.cluster.local
nslookup: can't resolve '(null)': Name does not resolve

nslookup: can't resolve 'jenkins.build-env.svc.cluster.local': Try again
command terminated with exit code 1
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
And then I append one "dot" in the end of jenkins service url

$ kubectl --namespace=build-env exec -it slave-0cnkz-gv0bg --container=worker nslookup jenkins.build-env.svc.cluster.local.
nslookup: can't resolve '(null)': Name does not resolve

Name:      jenkins.build-env.svc.cluster.local.
Address 1: 10.100.146.119 jenkins.build-env.svc.cluster.local
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
$ kubectl --namespace=build-env exec -it slave-0cnkz-gv0bg --container=worker nslookup jenkins.build-env
nslookup: can't resolve '(null)': Name does not resolve

Name:      jenkins.build-env
Address 1: 10.100.146.119
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
kubectl --namespace=build-env exec -it slave-0cnkz-gv0bg --container=worker curl http://jenkins.build-env:8080/tcpSlaveAgentListener/


  Jenkins
---------------------------------------------------------------------------------------------------------------------------------------------------------------------

So do you know why FQDN can't be resolved by DNS?
JNLP is also in the same pod.
Suppose that JNLP container and worker container should have the same behavior, right?

Thanks.

Hong

[YAN-HONG WANG]

Hello Carlos,

I fixed problem already.
Thanks.

Hong

[pbasan...@gmail.com]

Hi Hong,

We are hitting the Same error as mentioned above .. Can you please share the steps followed to resolve this error.

=============

Nov 16, 2017 6:22:51 AM hudson.remoting.jnlp.Main$CuiListener error

SEVERE: Failed to connect to http://slc13pef.us.oracle.com:8080/tcpSlaveAgentListener/: slc13pef.us.oracle.com

java.io.IOException: Failed to connect to http://slc13pef.us.oracle.com:8080/tcpSlaveAgentListener/: slc13pef.us.oracle.com

        at org.jenkinsci.remoting.engine.JnlpAgentEndpointResolver.resolve(JnlpAgentEndpointResolver.java:161)

        at hudson.remoting.Engine.innerRun(Engine.java:495)

        at hudson.remoting.Engine.run(Engine.java:447)

Caused by: java.net.UnknownHostException: slc13pef.us.oracle.com

 

==================

Regards,

Basanta

[YAN-HONG WANG]

Hello,

Do you use Ubuntu machine to be your base?

Hong

[pbasan...@gmail.com]

Hi Hong,

We are using Linux machine 

But i think the issue reported on this thread is nothing to do with Operating System.

Regards,

Basanta

[pbasan...@gmail.com]

Hi Hong,

Here is the detail of the Environment 

Installed k8s and Jenkins on the one Master server (Linux) and the jobs are running on Master.(with out slave nodes)

But when we tried on 1 Master and 2 slave nodes , the jobs are failing with error 

=============

Nov 16, 2017 6:22:51 AM hudson.remoting.jnlp.Main$CuiListener error

SEVERE: Failed to connect to http://slc13pef.us.oracle.com:8080/tcpSlaveAgentListener/: slc13pef.us.oracle.com

java.io.IOException: Failed to connect to http://slc13pef.us.oracle.com:8080/tcpSlaveAgentListener/: slc13pef.us.oracle.com

        at org.jenkinsci.remoting.engine.JnlpAgentEndpointResolver.resolve(JnlpAgentEndpointResolver.java:161)

        at hudson.remoting.Engine.innerRun(Engine.java:495)

        at hudson.remoting.Engine.run(Engine.java:447)

Caused by: java.net.UnknownHostException: slc13pef.us.oracle.com

==================

Here we installed Jenkins and not using as a service.

Regards,

Basanta

[YAN-HONG WANG]

Hi Basanta,

Because the DNS mechanism seem are different in Ubuntu and CentOS.
If using CentOS, and install K8S by default way maybe not a problem.

But, in Ubuntu. I need to add nameserver into /etc/resolvconf/resolv.conf.d/head or /etc/resolvconf/resolv.conf.d/tail.
And then 'resolvconf -u' update /etc/resolv.conf. So kubeadm will also add my nameserver into K8S.

That's my environment condition.

Hope this help you.

Hong

[WANG, YAN-HONG]

You use Jenkins, but not using as a service?

Or?

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[pbasan...@gmail.com]

Yes we installed Jenkins separately (not on K8s cluster).

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[WANG, YAN-HONG]

In my case, we run Jenkins also in K8S. So Jenkins expose with K8S service.

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