cannot query kubernetes (unauthorized): endpoints is forbidden: User cannot list endpoints in the namespace

Question

I am running kubernetes 1.9.4 on my gke cluster

I have two pods , gate which is trying to connect to coolapp, both written in elixir

I am using libcluster to connect my nodes I get the following error:

[libcluster:app_name] cannot query kubernetes (unauthorized): endpoints is forbidden: User "system:serviceaccount:staging:default" cannot list endpoints in the namespace "staging": Unknown user "system:serviceaccount:staging:default"

here is my config in gate under config/prod:

 config :libcluster,
 topologies: [
   app_name: [
     strategy: Cluster.Strategy.Kubernetes,
     config: [
       kubernetes_selector: "tier=backend",
       kubernetes_node_basename: System.get_env("MY_POD_NAMESPACE") || "${MY_POD_NAMESPACE}"]]]

here is my configuration:

vm-args

## Name of the node
-name ${MY_POD_NAMESPACE}@${MY_POD_IP}
## Cookie for distributed erlang
-setcookie ${ERLANG_COOKIE}
# Enable SMP automatically based on availability
-smp auto

creating the secrets:

kubectl create secret generic erlang-config --namespace staging --from-literal=erlang-cookie=xxxxxx
kubectl create configmap vm-config --namespace staging --from-file=vm.args

gate/deployment.yaml

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: gate
  namespace: staging
spec:
  replicas: 1
  revisionHistoryLimit: 1
  strategy:
      type: RollingUpdate
  template:
    metadata:
      labels:
        app: gate
        tier: backend
    spec:
      securityContext:
        runAsUser: 0
        runAsNonRoot: false
      containers:
      - name: gate
        image: gcr.io/development/gate:0.1.7
        args:
          - foreground
        ports:
        - containerPort: 80
        volumeMounts:
        - name: config-volume
          mountPath: /beamconfig
        env:
        - name: MY_POD_NAMESPACE
          value: staging
        - name: MY_POD_IP
          valueFrom:
            fieldRef:
              fieldPath: status.podIP
        - name: MY_POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: RELEASE_CONFIG_DIR
          value: /beamconfig
        - name: ERLANG_COOKIE
          valueFrom:
            secretKeyRef:
              name: erlang-config
              key: erlang-cookie
      volumes:
      - name: config-volume
        configMap:
          name: vm-config

coolapp/deployment.yaml:

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: coolapp
  namespace: staging
spec:
  replicas: 1
  revisionHistoryLimit: 1
  strategy:
      type: RollingUpdate
  template:
    metadata:
      labels:
        app: coolapp
        tier: backend
    spec:
      securityContext:
        runAsUser: 0
        runAsNonRoot: false
     # volumes
      volumes:
      - name: config-volume
        configMap:
          name: vm-config
      containers:
      - name: coolapp
        image: gcr.io/development/coolapp:1.0.3
        volumeMounts:
        - name: secrets-volume
          mountPath: /secrets
          readOnly: true
        - name: config-volume
          mountPath: /beamconfig
        ports:
        - containerPort: 80
        args:
          - "foreground"
        env:
        - name: MY_POD_NAMESPACE
          value: staging
        - name: MY_POD_IP
          valueFrom:
            fieldRef:
              fieldPath: status.podIP
        - name: MY_POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: REPLACE_OS_VARS
          value: "true"
        - name: RELEASE_CONFIG_DIR
          value: /beamconfig
        - name: ERLANG_COOKIE
          valueFrom:
            secretKeyRef:
              name: erlang-config
              key: erlang-cookie
        # proxy_container
      - name: cloudsql-proxy
        image: gcr.io/cloudsql-docker/gce-proxy:1.11
        command: ["/cloud_sql_proxy", "--dir=/cloudsql",
            "-instances=staging:us-central1:com-staging=tcp:5432",
            "-credential_file=/secrets/cloudsql/credentials.json"]
        volumeMounts:
          - name: cloudsql-instance-credentials
            mountPath: /secrets/cloudsql
            readOnly: true
          - name: cloudsql
            mountPath: /cloudsql

Answer 1

The default service account for the staging namespace (in which apparently your Pods using libcluster are running) lacks RBAC permissions to get endpoints in that namespace.

Likely your application requires a number of other permissions (that are not mentioned in the above error message) to work correctly; identifying all such permissions is out of scope for SO.

A way to resolve this issue is to grant superuser permissions that service account. This is not a secure solution but a stop gap fix.

$ kubectl create clusterrolebinding make-staging-sa-cluster-admin \
    --serviceaccount=staging:default \
    --clusterrole=cluster-admin

clusterrolebinding "make-staging-sa-cluster-admin" created

To grant the specific permission only (get endpoints in the staging namespace) you would need to create a Role first:

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: some-permissions
  namespace: staging
rules:
- apiGroups: [""]
  resources: ["endpoints"]
  verbs: ["get", "list", "watch"]

And create a RoleBinding for the default service account in the staging namespace:

apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: give-default-sa-some-permissions
  namespace: staging
subjects:
- kind: ServiceAccount
  name: default
  namespace: staging
roleRef:
  kind: Role
  name: some-permissions
  apiGroup: rbac.authorization.k8s.io

Answer 2

Not an erlang/elixir or libcluster user, but it seems it is trying to use the default service account for the namespace to try and query the master for a list of endpoints available in the cluster.

The readme for libcluster says as much:

If set to Cluster.Strategy.Kubernetes, it will use the Kubernetes API to query endpoints based on a basename and label selector, using the token and namespace injected into every pod; once it has a list of endpoints, it uses that list to form a cluster, and keep it up to date.

Reading the code for the kubernetes.ex in libcluster and the error you get confirm as much.

You will need to setup a ClusterRole and RoleBinding for the service account in the staging namespace. This will allow libcluster to dynamically query the master to discover other erlang nodes in the cluster/namespace.

Here are some handy resources for follow up reading:

• https://kubernetes.io/docs/admin/service-accounts-admin/
• https://kubernetes.io/docs/admin/authorization/rbac/
• https://kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/