add ability to filter the list of pods to be drained by a pod label selector (#606)

* add ability to filter the list of pods to be drained by a label selector

changelogs/fragments/606-k8s_drain-add-pod_selectors-parameter.yaml

@@ -0,0 +1,3 @@
+---
+minor_changes:
+  - k8s_drain - add ability to filter the list of pods to be drained by a pod label selector (https://github.com/ansible-collections/kubernetes.core/issues/474).

plugins/modules/k8s_drain.py

@@ -41,6 +41,15 @@ options:
       - The name of the node.
     required: true
     type: str
+  pod_selectors:
+    description:
+      - Label selector to filter pods on the node.
+      - This option has effect only when C(state) is set to I(drain).
+    type: list
+    elements: str
+    version_added: 2.5.0
+    aliases:
+    - label_selectors
   delete_options:
     type: dict
     default: {}
@@ -116,6 +125,14 @@ EXAMPLES = r"""
     state: cordon
     name: foo
 
+- name: Drain node "foo" using label selector to filter the list of pods to be drained.
+  kubernetes.core.k8s_drain:
+    state: drain
+    name: foo
+    pod_selectors:
+    - 'app!=csi-attacher'
+    - 'app!=csi-provisioner'
+
 """
 
 RETURN = r"""
@@ -329,6 +346,17 @@ class K8sDrainAnsible(object):
                     )
                 )
 
+    def list_pods(self):
+        params = {
+            "field_selector": "spec.nodeName={name}".format(
+                name=self._module.params.get("name")
+            )
+        }
+        pod_selectors = self._module.params.get("pod_selectors")
+        if pod_selectors:
+            params["label_selector"] = ",".join(pod_selectors)
+        return self._api_instance.list_pod_for_all_namespaces(**params)
+
     def delete_or_evict_pods(self, node_unschedulable):
         # Mark node as unschedulable
         result = []
@@ -351,12 +379,7 @@ class K8sDrainAnsible(object):
                 self.patch_node(unschedulable=False)
 
         try:
-            field_selector = "spec.nodeName={name}".format(
+            pod_list = self.list_pods()
-                name=self._module.params.get("name")
-            )
-            pod_list = self._api_instance.list_pod_for_all_namespaces(
-                field_selector=field_selector
-            )
             # Filter pods
             force = self._drain_options.get("force", False)
             ignore_daemonset = self._drain_options.get("ignore_daemonsets", False)
@@ -487,6 +510,11 @@ def argspec():
                     wait_sleep=dict(type="int", default=5),
                 ),
             ),
+            pod_selectors=dict(
+                type="list",
+                elements="str",
+                aliases=["label_selectors"],
+            ),
         )
     )
     return argument_spec

tests/integration/targets/k8s_drain/tasks/main.yml

@@ -281,6 +281,7 @@
       that:
       - dset_result.resources | list | length > 0
 
+  # test: drain using disable_eviction=true
   - name: Uncordon node
     k8s_drain:
       state: uncordon
@@ -347,6 +348,90 @@
     register: _result
     failed_when: _result.resources
 
+  # test: drain using pod_selectors
+  - name: Uncordon node
+    k8s_drain:
+      state: uncordon
+      name: '{{ node_to_drain }}'
+
+  - name: create a Pod for test
+    k8s:
+      namespace: '{{ test_namespace }}'
+      wait: true
+      wait_timeout: "{{ k8s_wait_timeout | default(omit) }}"
+      definition:
+        apiVersion: v1
+        kind: Pod
+        metadata:
+          name: 'ansible-drain-pod'
+          labels:
+            app: ansible-drain
+        spec:
+          affinity:
+            nodeAffinity:
+              requiredDuringSchedulingIgnoredDuringExecution:
+                nodeSelectorTerms:
+                - matchFields:
+                  - key: metadata.name
+                    operator: In
+                    values:
+                    - '{{ node_to_drain }}'
+          containers:
+          - name: ansible-container
+            image: busybox
+            command:
+            - '/bin/sh'
+            - '-c'
+            - 'while true; do echo $(date); sleep 10; done'
+
+  - name: Drain node using pod_selectors 'app!=ansible-drain'
+    k8s_drain:
+      state: drain
+      name: '{{ node_to_drain }}'
+      pod_selectors:
+      - app!=ansible-drain
+      delete_options:
+        terminate_grace_period: 0
+        delete_emptydir_data: true
+        force: true
+        ignore_daemonsets: true
+    register: drain_pod_selector
+
+  - name: assert that node has been drained
+    assert:
+      that:
+      - drain_pod_selector is changed
+      - '"node {{ node_to_drain }} marked unschedulable." in drain_pod_selector.result'
+
+  - name: assert that pod created before is still running
+    k8s_info:
+      namespace: '{{ test_namespace }}'
+      kind: Pod
+      label_selectors:
+      - app=ansible-drain
+      field_selectors:
+      - status.phase=Running
+    register: pods
+    failed_when: pods.resources == []
+
+  - name: Drain node using pod_selectors 'app=ansible-drain'
+    k8s_drain:
+      state: drain
+      name: '{{ node_to_drain }}'
+      pod_selectors:
+      - app=ansible-drain
+      delete_options:
+        terminate_grace_period: 0
+        force: true
+    register: drain_pod_selector_equal
+
+  - name: assert that node was not drained
+    assert:
+      that:
+      - drain_pod_selector_equal is changed
+      - '"node {{ node_to_drain }} already marked unschedulable." in drain_pod_selector_equal.result'
+      - '"Deleting Pods not managed by ReplicationController, ReplicaSet, Job, DaemonSet or StatefulSet: {{ test_namespace }}/ansible-drain-pod." in drain_pod_selector_equal.warnings'
+
   - name: Uncordon node
     k8s_drain:
       state: uncordon