Im trying to upgrade kube cluster from Ubuntu 16 to 18. After the upgrade kube-dns pod is constantly crashing. The problem appears only on U18 if i'm rolling back to U16 everything works fine.
Kube version "v1.10.11"
kube-dns pod events:
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 28m default-scheduler Successfully assigned kube-dns-75966d58fb-pqxz4 to
Normal SuccessfulMountVolume 28m kubelet, MountVolume.SetUp succeeded for volume "kube-dns-config"
Normal SuccessfulMountVolume 28m kubelet, MountVolume.SetUp succeeded for volume "kube-dns-token-h4q66"
Normal Pulling 28m kubelet, pulling image "k8s.gcr.io/k8s-dns-kube-dns-amd64:1.14.10"
Normal Pulled 28m kubelet, Successfully pulled image "k8s.gcr.io/k8s-dns-kube-dns-amd64:1.14.10"
Normal Started 28m kubelet, Started container
Normal Created 28m kubelet, Created container
Normal Pulling 28m kubelet, pulling image "k8s.gcr.io/k8s-dns-dnsmasq-nanny-amd64:1.14.10"
Normal Pulling 28m kubelet, pulling image "k8s.gcr.io/k8s-dns-sidecar-amd64:1.14.10"
Normal Pulled 28m kubelet, Successfully pulled image "k8s.gcr.io/k8s-dns-dnsmasq-nanny-amd64:1.14.10"
Normal Created 28m kubelet, Created container
Normal Pulled 28m kubelet, Successfully pulled image "k8s.gcr.io/k8s-dns-sidecar-amd64:1.14.10"
Normal Started 28m kubelet, Started container
Normal Created 25m (x2 over 28m) kubelet, Created container
Normal Started 25m (x2 over 28m) kubelet, Started container
Normal Killing 25m kubelet, Killing container with id docker://dnsmasq:Container failed liveness probe.. Container will be killed and recreated.
Normal Pulled 25m kubelet, Container image "k8s.gcr.io/k8s-dns-dnsmasq-nanny-amd64:1.14.10" already present on machine
Warning Unhealthy 4m (x26 over 27m) kubelet, Liveness probe failed: HTTP probe failed with statuscode: 503kube-dns sidecar container logs:
kubectl logs kube-dns-75966d58fb-pqxz4 -n kube-system -c sidecar
I0809 16:31:26.768964 1 main.go:51] Version v1.14.8.3
I0809 16:31:26.769049 1 server.go:45] Starting server (options {DnsMasqPort:53 DnsMasqAddr:127.0.0.1 DnsMasqPollIntervalMs:5000 Probes:[{Label:kubedns Server:127.0.0.1:10053 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1} {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}] PrometheusAddr:0.0.0.0 PrometheusPort:10054 PrometheusPath:/metrics PrometheusNamespace:kubedns})
I0809 16:31:26.769079 1 dnsprobe.go:75] Starting dnsProbe {Label:kubedns Server:127.0.0.1:10053 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}
I0809 16:31:26.769117 1 dnsprobe.go:75] Starting dnsProbe {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}
W0809 16:31:33.770594 1 server.go:64] Error getting metrics from dnsmasq: read udp 127.0.0.1:49305->127.0.0.1:53: i/o timeout
W0809 16:31:40.771166 1 server.go:64] Error getting metrics from dnsmasq: read udp 127.0.0.1:49655->127.0.0.1:53: i/o timeout
W0809 16:31:47.771773 1 server.go:64] Error getting metrics from dnsmasq: read udp 127.0.0.1:53322->127.0.0.1:53: i/o timeout
W0809 16:31:54.772386 1 server.go:64] Error getting metrics from dnsmasq: read udp 127.0.0.1:58999->127.0.0.1:53: i/o timeout
W0809 16:32:01.772972 1 server.go:64] Error getting metrics from dnsmasq: read udp 127.0.0.1:35034->127.0.0.1:53: i/o timeout
W0809 16:32:08.773540 1 server.go:64] Error getting metrics from dnsmasq: read udp 127.0.0.1:33250->127.0.0.1:53: i/o timeoutkube-dns dnsmasq container logs:
kubectl logs kube-dns-75966d58fb-pqxz4 -n kube-system -c dnsmasq
I0809 16:29:51.596517 1 main.go:74] opts: {{/usr/sbin/dnsmasq [-k --cache-size=1000 --dns-forward-max=150 --no-negcache --log-facility=- --server=/cluster.local/127.0.0.1#10053 --server=/in-addr.arpa/127.0.0.1#10053 --server=/in6.arpa/127.0.0.1#10053] true} /etc/k8s/dns/dnsmasq-nanny 10000000000}
I0809 16:29:51.596679 1 nanny.go:94] Starting dnsmasq [-k --cache-size=1000 --dns-forward-max=150 --no-negcache --log-facility=- --server=/cluster.local/127.0.0.1#10053 --server=/in-addr.arpa/127.0.0.1#10053 --server=/in6.arpa/127.0.0.1#10053]
I0809 16:29:52.135179 1 nanny.go:119]
W0809 16:29:52.135211 1 nanny.go:120] Got EOF from stdout
I0809 16:29:52.135277 1 nanny.go:116] dnsmasq[20]: started, version 2.78 cachesize 1000
I0809 16:29:52.135293 1 nanny.go:116] dnsmasq[20]: compile time options: IPv6 GNU-getopt no-DBus no-i18n no-IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset auth no-DNSSEC loop-detect inotify
I0809 16:29:52.135303 1 nanny.go:116] dnsmasq[20]: using nameserver 127.0.0.1#10053 for domain in6.arpa
I0809 16:29:52.135314 1 nanny.go:116] dnsmasq[20]: using nameserver 127.0.0.1#10053 for domain in-addr.arpa
I0809 16:29:52.135323 1 nanny.go:116] dnsmasq[20]: using nameserver 127.0.0.1#10053 for domain cluster.local
I0809 16:29:52.135329 1 nanny.go:116] dnsmasq[20]: reading /etc/resolv.conf
I0809 16:29:52.135334 1 nanny.go:116] dnsmasq[20]: using nameserver 127.0.0.1#10053 for domain in6.arpa
I0809 16:29:52.135343 1 nanny.go:116] dnsmasq[20]: using nameserver 127.0.0.1#10053 for domain in-addr.arpa
I0809 16:29:52.135348 1 nanny.go:116] dnsmasq[20]: using nameserver 127.0.0.1#10053 for domain cluster.local
I0809 16:29:52.135353 1 nanny.go:116] dnsmasq[20]: using nameserver 127.0.0.53#53
I0809 16:29:52.135397 1 nanny.go:116] dnsmasq[20]: read /etc/hosts - 7 addresses
I0809 16:31:28.728897 1 nanny.go:116] dnsmasq[20]: Maximum number of concurrent DNS queries reached (max: 150)
I0809 16:31:38.746899 1 nanny.go:116] dnsmasq[20]: Maximum number of concurrent DNS queries reached (max: 150)I have deleted the existing pods but newly created getting same error after some time. Not sure why this is happening only on Ubuntu 18. Any ideas how to fix this?
Ubuntu 18 uses systemd-resolved as DNS server which listens on 127.0.0.53. You can take a look at your resolv.conf file. When /etc/resolv.conf is mapped to CoreDNS, it is acted as upstream DNS server, however the loop detection plugin failed. You can take a look at the CoreDNS troubleshooting page
In my Ubuntu 18 cluster, I disabled systemd-resolved.
In my case i have found that in ubuntu18 the resolve.conf was pointing pointing to: /etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf and it had nameserver 127.0.0.53 entry. At the same time under /run/systemd/resolve you should have another resolv.conf
/run/systemd/resolve$ ll
total 8
drwxr-xr-x 2 systemd-resolve systemd-resolve 80 Aug 12 13:24 ./
drwxr-xr-x 23 root root 520 Aug 12 11:54 ../
-rw-r--r-- 1 systemd-resolve systemd-resolve 607 Aug 12 13:24 resolv.conf
-rw-r--r-- 1 systemd-resolve systemd-resolve 735 Aug 12 13:24 stub-resolv.confIn my case resolv.conf contains private IP nameserver 172.27.0.2. Just relink to the ../run/systemd/resolve/resolv.conf on all cluster machines and reboot the kube-dns pods.