refreshing snap from 1.13/stable to 1.15/stable fails

The following sequence results in reproducible failures with the following inputs / outputs.

root@devstand:~# snap switch --channel=1.15/stable microk8s
"microk8s" switched to the "1.15/stable" channel

root@devstand:~# snap refresh --list
Name      Version  Rev  Publisher   Notes
microk8s  v1.15.3  825  canonical✓  classic
consider re-refresh of "microk8s"
root@devstand:~# snap refresh --classic microk8s
error: cannot perform the following tasks:
- Run configure hook of "microk8s" snap if present (run hook "configure":
-----
+ source /snap/microk8s/825/actions/common/utils.sh
+ '[' '!' -d /var/snap/microk8s/825/certs ']'
+ '[' '!' -f /var/snap/microk8s/825/certs/csr.conf.template ']'
+ cp /snap/microk8s/825/certs/csr.conf.template /var/snap/microk8s/825/certs/csr.conf.template
+ grep requestheader-client-ca-file /var/snap/microk8s/825/args/kube-apiserver
--requestheader-client-ca-file=${SNAP_DATA}/certs/ca.crt
+ grep -E -- '--(requestheader-allowed-names|requestheader-extra-headers-prefix|requestheader-group-headers|requestheader-username-headers|proxy-client-cert-file|proxy-client-key-file)=' /var/snap/microk8s/825/args/kube-apiserver
+ echo 'Enabling Enable the aggregation layer'
Enabling Enable the aggregation layer
+ echo ''
+ echo --requestheader-allowed-names=front-proxy-client
+ echo --requestheader-extra-headers-prefix=X-Remote-Extra-
+ echo --requestheader-group-headers=X-Remote-Group
+ echo --requestheader-username-headers=X-Remote-User
+ echo '--proxy-client-cert-file=${SNAP_DATA}/certs/front-proxy-client.crt'
+ echo '--proxy-client-key-file=${SNAP_DATA}/certs/front-proxy-client.key'
+ systemctl restart snap.microk8s.daemon-apiserver
+ grep -e requestheader-client-ca-file=/var/snap/microk8s/.../certs/ca.crt /var/snap/microk8s/825/args/kube-apiserver
+ mkdir -p /var/snap/microk8s/825/var/lock/
+ '[' '!' -f /var/snap/microk8s/825/credentials/client.config ']'
+ echo 'Patching client config location'
Patching client config location
+ mkdir -p /var/snap/microk8s/825/credentials/
+ cp /snap/microk8s/825/client.config /var/snap/microk8s/825/credentials/
cp: cannot stat '/snap/microk8s/825/client.config': No such file or directory
-----)

root@devstand:~# snap tasks 32
Status  Spawn               Ready               Summary
Done    today at 14:52 PDT  today at 14:53 PDT  Ensure prerequisites for "microk8s" are available
Undone  today at 14:52 PDT  today at 14:53 PDT  Download snap "microk8s" (825) from channel "1.15/stable"
Done    today at 14:52 PDT  today at 14:53 PDT  Fetch and check assertions for snap "microk8s" (825)
Undone  today at 14:52 PDT  today at 14:53 PDT  Mount snap "microk8s" (825)
Undone  today at 14:52 PDT  today at 14:53 PDT  Run pre-refresh hook of "microk8s" snap if present
Undone  today at 14:52 PDT  today at 14:53 PDT  Stop snap "microk8s" services
Undone  today at 14:52 PDT  today at 14:53 PDT  Remove aliases for snap "microk8s"
Undone  today at 14:52 PDT  today at 14:53 PDT  Make current revision for snap "microk8s" unavailable
Undone  today at 14:52 PDT  today at 14:53 PDT  Copy snap "microk8s" data
Undone  today at 14:52 PDT  today at 14:53 PDT  Setup snap "microk8s" (825) security profiles
Undone  today at 14:52 PDT  today at 14:53 PDT  Make snap "microk8s" (825) available to the system
Undone  today at 14:52 PDT  today at 14:53 PDT  Automatically connect eligible plugs and slots of snap "microk8s"
Undone  today at 14:52 PDT  today at 14:53 PDT  Set automatic aliases for snap "microk8s"
Undone  today at 14:52 PDT  today at 14:53 PDT  Setup snap "microk8s" aliases
Undone  today at 14:52 PDT  today at 14:53 PDT  Run post-refresh hook of "microk8s" snap if present
Undone  today at 14:52 PDT  today at 14:53 PDT  Start snap "microk8s" (825) services
Done    today at 14:52 PDT  today at 14:53 PDT  Clean up "microk8s" (825) install
Error   today at 14:52 PDT  today at 14:53 PDT  Run configure hook of "microk8s" snap if present
Hold    today at 14:52 PDT  today at 14:53 PDT  Run health check of "microk8s" snap
Done    today at 14:52 PDT  today at 14:53 PDT  Consider re-refresh of "microk8s"

......................................................................
Run configure hook of "microk8s" snap if present

2019-09-11T14:53:26-07:00 ERROR run hook "configure": 
-----
+ source /snap/microk8s/825/actions/common/utils.sh
+ '[' '!' -d /var/snap/microk8s/825/certs ']'
+ '[' '!' -f /var/snap/microk8s/825/certs/csr.conf.template ']'
+ cp /snap/microk8s/825/certs/csr.conf.template /var/snap/microk8s/825/certs/csr.conf.template
+ grep requestheader-client-ca-file /var/snap/microk8s/825/args/kube-apiserver
--requestheader-client-ca-file=${SNAP_DATA}/certs/ca.crt
+ grep -E -- '--(requestheader-allowed-names|requestheader-extra-headers-prefix|requestheader-group-headers|requestheader-username-headers|proxy-client-cert-file|proxy-client-key-file)=' /var/snap/microk8s/825/args/kube-apiserver
+ echo 'Enabling Enable the aggregation layer'
Enabling Enable the aggregation layer
+ echo ''
+ echo --requestheader-allowed-names=front-proxy-client
+ echo --requestheader-extra-headers-prefix=X-Remote-Extra-
+ echo --requestheader-group-headers=X-Remote-Group
+ echo --requestheader-username-headers=X-Remote-User
+ echo '--proxy-client-cert-file=${SNAP_DATA}/certs/front-proxy-client.crt'
+ echo '--proxy-client-key-file=${SNAP_DATA}/certs/front-proxy-client.key'
+ systemctl restart snap.microk8s.daemon-apiserver
+ grep -e requestheader-client-ca-file=/var/snap/microk8s/.../certs/ca.crt /var/snap/microk8s/825/args/kube-apiserver
+ mkdir -p /var/snap/microk8s/825/var/lock/
+ '[' '!' -f /var/snap/microk8s/825/credentials/client.config ']'
+ echo 'Patching client config location'
Patching client config location
+ mkdir -p /var/snap/microk8s/825/credentials/
+ cp /snap/microk8s/825/client.config /var/snap/microk8s/825/credentials/
cp: cannot stat '/snap/microk8s/825/client.config': No such file or directory
-----

[ktsakalozos]

The fix should be on edge now. Try upgradind to 1.15/edge.

[lazzarello]

Great! The refresh works as intended, but I found another side effect of replacing docker with containerd. The DNS plugin gets stuck with the following sequence:

sudo snap install --classic --channel=1.13/stable microk8s
microk8s.enable dns
sudo snap refresh --classic --channel=1.15/edge microk8s
microk8s.disable dns
kubectl delete pod -n kube-system kube-dns-*

It tries to delete the pod by looking for a docker socket, which is no longer present so it is stuck in the state Terminating.

Additionally, after the refresh, I cannot create interactive pods. The following fails with this output

microk8s.kubectl run example --rm --image=busybox -it
deployment.apps "example" deleted
error: timed out waiting for the condition

Removing microk8s and installing 1.15/edge and repeating the above succeeds.