update README, examples and RBAC to include leader election

Author: andrewsykim

README.md

@@ -48,6 +48,13 @@ It is necessary to create a new service account and give it enough privileges to
 for i in $(find deploy/kubernetes -name '*.yaml'); do kubectl create -f $i; done
 ```
 
+### Running with Leader Election
+
+If you want to run external-snapshotter with higher availability, you can enable resource based leader election. To enable this, set the following flags:
+```bash
+--leader-election=true
+```
+
 ## Testing
 
 Running Unit Tests:

deploy/kubernetes/rbac-external-provisioner.yaml

@@ -59,7 +59,7 @@ roleRef:
   apiGroup: rbac.authorization.k8s.io
 
 ---
-# Provisioner must be able to work with endpoints in current namespace
+# Provisioner must be able to work with endpoints and leases in current namespace
 # if (and only if) leadership election is enabled
 kind: Role
 apiVersion: rbac.authorization.k8s.io/v1
@@ -71,6 +71,9 @@ rules:
 - apiGroups: [""]
   resources: ["endpoints"]
   verbs: ["get", "watch", "list", "delete", "update", "create"]
+- apiGroups: ["coordination.k8s.io"]
+  resources: ["leases"]
+  verbs: ["get", "watch", "list", "delete", "update", "create"]
 
 ---
 kind: RoleBinding

deploy/kubernetes/rbac.yaml

@@ -47,6 +47,10 @@ rules:
   - apiGroups: ["apiextensions.k8s.io"]
     resources: ["customresourcedefinitions"]
     verbs: ["create", "list", "watch", "delete"]
+    # access to leases is required for leader election
+  - apiGroups: ["coordination.k8s.io"]
+    resources: ["leases"]
+    verbs: ["get", "watch", "list", "delete", "update", "create"]
 
 ---
 kind: ClusterRoleBinding

deploy/kubernetes/setup-csi-snapshotter.yaml

@@ -89,6 +89,7 @@ spec:
           args:
             - "--csi-address=$(ADDRESS)"
             - "--connection-timeout=15s"
+            - "--leader-election=true"
           env:
             - name: ADDRESS
               value: /csi/csi.sock