coredump-detector

Coredump-detector is a MutatingAdmissionWebhook. It mounts a persistent volume claim to a specific directory in every container of the pod. And add a NodeSelector to the pod, so that the pod will be scheduled to a node that supports coredump. Here supports coredump means the kernel will generate the coredump file into the mounted persistent volume.

How does cluster admin deploy it?

how to deploy it outside of cluster

See INSTALL_OUT_CLUSTER.md

how to deploy it as a k8s service

See INSTALL_AS_SERVICE.md

How tenant use the feature

1. Declare a rwx persistent volume claim (see: https://kubernetes.io/docs/concepts/storage/persistent-volumes/)
2. When creating a pod, add an annotation to the pod(or pod template if you are creating a deployment or so) like this:

apiVersion: v1
kind: Pod
metadata:
  annotations:
    "coredump.fujitsu.com/pvcname": myclaim  # here myclaim is the rwx persistent volume claim created in step one
  name: example

3. Check the volume and nodeSelector in the pod spec. When run kubectl get pods foo -o yaml, you can see MutatingAdmissionWebhook has modified the pod:

apiVersion: v1
items:
- apiVersion: v1
  kind: Pod
  metadata:
    annotations:
      coredump.fujitsu.com/pvcname: myclaim
      kubernetes.io/psp: privileged
    namespace: default
  spec:
    nodeSelector:
      # this is new added
      coredump: "true"
    containers:
    - command:
      - sleep
      - "10000"
      image: busybox
      # this is new added
      name: example
      volumeMounts:
      - mountPath: /var/coredump
        name: myclaim-1528858878
        subPath: example/example

4. check the mount path inside the container:

$ kubectl exec -it example sh
$ mount |grep coredump
172.16.29.130:/nfs/example/example on /var/coredump type nfs4 (rw,relatime,vers=4.0,rsize=524288,wsize=524288,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=172.16.29.129,local_lock=none,addr=172.16.29.130)

5. Now the core files are all saved in your persistent volume claim.

known issues

1. it can't work well with command kubectl apply -f. See: kubernetes/kubernetes#64944