On a new cluster we saw the following logs from an application we launched:

2018/06/15 20:20:43.840 WARN  [grpc-default-executor-8] [ManagedChannelImpl] [ManagedChannelImpl$NameResolverListenerImpl:942] [io.grpc.internal.ManagedChannelImpl-17247] Failed to resolve name. status=Status{code=UNAVAILABLE, description=Unable to resolve host pubsub.googleapis.com, cause=java.net.UnknownHostException: pubsub.googleapis.com
	at java.net.InetAddress.getAllByName0(InetAddress.java:1280)
	at java.net.InetAddress.getAllByName(InetAddress.java:1192)
	at java.net.InetAddress.getAllByName(InetAddress.java:1126)
	at io.grpc.internal.DnsNameResolver$JdkResolver.resolve(DnsNameResolver.java:358)
	at io.grpc.internal.DnsNameResolver$1.run(DnsNameResolver.java:172)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)

The pod didnt have ping but it had curl. Tried curling the endpoint pubsub.googleapis.com that it was trying to reach but that didnt work. Tried curling google.com and that didnt work.

Then I went to another pod that had ping to give it a try.

root@ingress-controller-external-7bc9767f69-7qxfb:/# ping google.com
ping: unknown host

Cant resolve any hostnames either. Tried to ping a known IP:

root@ingress-controller-external-7bc9767f69-7qxfb:/# ping
PING ( 56 data bytes
64 bytes from icmp_seq=0 ttl=51 time=0.941 ms
64 bytes from icmp_seq=1 ttl=51 time=0.346 ms

That worked. This would make sense since the instance was able to pull the container image with a hostname. It would seem DNS and routing were working on the GCE instance level.

This lead me to think it was something wrong with the kubernetes DNS.

Then I looked at the kube-systems namespace to see what the DNS were doing:

kube-dns-785f949785-5slck                                        0/4       Pending            0          23h       <none>       <none>
kube-dns-785f949785-w7str                                        0/4       Pending            0          23h       <none>       <none>
kube-dns-autoscaler-69c5cbdcdd-krfn9                             0/1       Pending            0          23h       <none>       <none>

They were still in pending state which would make sense.

This is showing there are a few level at play here from the instance to kubernetes

Contact me if you have any questions about this or want to chat, happy to start a dialog or help out: blogs@managedkube.com {::nomarkdown}

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