ceph_orch_apply: Improve by adding idempotency

library/ceph_orch_apply.py

@@ -15,15 +15,17 @@
 # limitations under the License.
 
 from __future__ import absolute_import, division, print_function
-from typing import List, Tuple
+from typing import List, Tuple, Dict
 __metaclass__ = type
 
+import datetime
+import yaml
+
 from ansible.module_utils.basic import AnsibleModule  # type: ignore
 try:
     from ansible.module_utils.ceph_common import exit_module, build_base_cmd_orch  # type: ignore
 except ImportError:
     from module_utils.ceph_common import exit_module, build_base_cmd_orch
-import datetime
 
 
 ANSIBLE_METADATA = {
@@ -70,6 +72,40 @@
 '''
 
 
+def parse_spec(spec: str) -> Dict:
+    """ parse spec string to yaml """
+    yaml_spec = yaml.safe_load(spec)
+    return yaml_spec
+
+
+def retrieve_current_spec(module: AnsibleModule, expected_spec: Dict) -> Dict:
+    """ retrieve current config of the service """
+    service: str = expected_spec["service_type"]
+    cmd = build_base_cmd_orch(module)
+    cmd.extend(['ls', service, '--format=yaml'])
+    out = module.run_command(cmd)
+    if isinstance(out, str):
+        # if there is no existing service, cephadm returns the string 'No services reported'
+        return {}
+    else:
+        return yaml.safe_load(out[1])
+
+
+def change_required(current: Dict, expected: Dict) -> bool:
+    """ checks if the current config differs from what is expected """
+    if not current:
+        return True
+
+    for key, value in expected.items():
+        if key in current:
+            if current[key] != value:
+                return True
+            continue
+        else:
+            return True
+    return False
+
+
 def apply_spec(module: "AnsibleModule",
                data: str) -> Tuple[int, List[str], str, str]:
     cmd = build_base_cmd_orch(module)
@@ -82,23 +118,24 @@ def apply_spec(module: "AnsibleModule",
     return rc, cmd, out, err
 
 
-def main() -> None:
+def run_module() -> None:
+
+    module_args = dict(
+        spec=dict(type='str', required=True),
+        fsid=dict(type='str', required=False),
+        docker=dict(type=bool,
+                    required=False,
+                    default=False),
+        image=dict(type='str', required=False)
+    )
+
     module = AnsibleModule(
-        argument_spec=dict(
-            fsid=dict(type='str', required=False),
-            spec=dict(type='str', required=True),
-            docker=dict(type=bool,
-                        required=False,
-                        default=False),
-            image=dict(type='str', required=False)
-        ),
+        argument_spec=module_args,
         supports_check_mode=True
     )
 
-    spec = module.params.get('spec')
-
     startd = datetime.datetime.now()
-    changed = False
+    spec = module.params.get('spec')
 
     if module.check_mode:
         exit_module(
@@ -111,8 +148,19 @@ def main() -> None:
             changed=False
         )
 
-    rc, cmd, out, err = apply_spec(module, spec)
-    changed = True
+    # Idempotency check
+    expected = parse_spec(module.params.get('spec'))
+    current_spec = retrieve_current_spec(module, expected)
+
+    if change_required(current_spec, expected):
+        rc, cmd, out, err = apply_spec(module, spec)
+        changed = True
+    else:
+        rc = 0
+        cmd = []
+        out = ''
+        err = ''
+        changed = False
 
     exit_module(
         module=module,
@@ -125,5 +173,9 @@ def main() -> None:
     )
 
 
+def main() -> None:
+    run_module()
+
+
 if __name__ == '__main__':
     main()

tox.ini

@@ -8,6 +8,7 @@ skipsdist = True
 basepython = python3
 deps =
     mypy
+    types-PyYAML
 commands = mypy --config-file ./mypy.ini {toxinidir}/library {toxinidir}/module_utils
 
 [testenv:flake8]