Add new meta task end_host (#47194)

* Add new meta task  end_host

changelogs/fragments/end-host-meta-task.yaml

@@ -0,0 +1,2 @@
+minor_changes:
+    - Add new meta task end_host - https://github.com/ansible/ansible/issues/40904

lib/ansible/modules/utilities/helper/meta.py

@@ -39,7 +39,8 @@ options:
         - "C(clear_host_errors) (added in 2.1) clears the failed state (if any) from hosts specified in the play's list of hosts."
         - "C(end_play) (added in 2.2) causes the play to end without failing the host(s). Note that this affects all hosts."
         - "C(reset_connection) (added in 2.3) interrupts a persistent connection (i.e. ssh + control persist)"
-    choices: ['flush_handlers', 'refresh_inventory', 'noop', 'clear_facts', 'clear_host_errors', 'end_play', 'reset_connection']
+        - "C(end_host) (added in 2.8) is a per-host variation of C(end_play). Causes the play to end for the current host without failing it."
+    choices: ['flush_handlers', 'refresh_inventory', 'noop', 'clear_facts', 'clear_host_errors', 'end_play', 'reset_connection', 'end_host']
     required: true
 notes:
     - C(meta) is not really a module nor action_plugin as such it cannot be overwritten.
@@ -77,4 +78,10 @@ EXAMPLES = '''
 - user: name={{ansible_user}} groups=input
 - name: reset ssh connection to allow user changes to affect 'current login user'
   meta: reset_connection
+
+- name: End the play for hosts that run CentOS 6
+  meta: end_host
+  when:
+    - ansible_distribution == 'CentOS'
+    - ansible_distribution_major_version == '6'
 '''

lib/ansible/plugins/strategy/__init__.py

@@ -1067,6 +1067,13 @@ class StrategyBase:
                     if host.name not in self._tqm._unreachable_hosts:
                         iterator._host_states[host.name].run_state = iterator.ITERATING_COMPLETE
                 msg = "ending play"
+        elif meta_action == 'end_host':
+            if _evaluate_conditional(target_host):
+                iterator._host_states[target_host.name].run_state = iterator.ITERATING_COMPLETE
+                msg = "ending play for %s" % target_host.name
+            else:
+                skipped = True
+                msg = "end_host conditional evaluated to false, continuing execution for %s" % target_host.name
         elif meta_action == 'reset_connection':
             all_vars = self._variable_manager.get_vars(play=iterator._play, host=target_host, task=task)
             templar = Templar(loader=self._loader, variables=all_vars)

lib/ansible/plugins/strategy/linear.py

@@ -265,7 +265,7 @@ class StrategyModule(StrategyBase):
                         # for the linear strategy, we run meta tasks just once and for
                         # all hosts currently being iterated over rather than one host
                         results.extend(self._execute_meta(task, play_context, iterator, host))
-                        if task.args.get('_raw_params', None) not in ('noop', 'reset_connection'):
+                        if task.args.get('_raw_params', None) not in ('noop', 'reset_connection', 'end_host'):
                             run_once = True
                         if (task.any_errors_fatal or run_once) and not task.ignore_errors:
                             any_errors_fatal = True

test/integration/targets/meta_tasks/aliases

@@ -0,0 +1 @@
+shippable/posix/group3

test/integration/targets/meta_tasks/runme.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+set -eux
+
+# test end_host meta task, with when conditional
+for test_strategy in linear free; do
+  out="$(ansible-playbook test_end_host.yml -i ../../inventory -e test_strategy=$test_strategy -vv "$@")"
+
+  grep -q "META: end_host conditional evaluated to false, continuing execution for testhost" <<< "$out"
+  grep -q "META: ending play for testhost2" <<< "$out"
+  grep -q "play not ended for testhost" <<< "$out"
+  grep -qv "play not ended for testhost2" <<< "$out"
+done
+
+# test end_host meta task, on all hosts
+for test_strategy in linear free; do
+  out="$(ansible-playbook test_end_host_all.yml -i ../../inventory -e test_strategy=$test_strategy -vv "$@")"
+
+  grep -q "META: ending play for testhost" <<< "$out"
+  grep -q "META: ending play for testhost2" <<< "$out"
+  grep -qv "play not ended for testhost" <<< "$out"
+  grep -qv "play not ended for testhost2" <<< "$out"
+done

test/integration/targets/meta_tasks/test_end_host.yml

@@ -0,0 +1,14 @@
+- name: "Testing end_host with strategy={{ test_strategy | default('linear') }}"
+  hosts:
+    - testhost
+    - testhost2
+  gather_facts: no
+  strategy: "{{ test_strategy | default('linear') }}"
+  tasks:
+    - debug:
+
+    - meta: end_host
+      when: "host_var_role_name == 'role2'"  # end play for testhost2, see test/integration/inventory
+
+    - debug:
+        msg: "play not ended for {{ inventory_hostname }}"

test/integration/targets/meta_tasks/test_end_host_all.yml

@@ -0,0 +1,13 @@
+- name: "Testing end_host all hosts with strategy={{ test_strategy | default('linear') }}"
+  hosts:
+    - testhost
+    - testhost2
+  gather_facts: no
+  strategy: "{{ test_strategy | default('linear') }}"
+  tasks:
+    - debug:
+
+    - meta: end_host
+
+    - debug:
+        msg: "play not ended {{ inventory_hostname }}"