From 7aae9e7e4d3c04a8f68d8b773f959a8e696cc6fd Mon Sep 17 00:00:00 2001
From: Jasper Misset <86775223+jmisset-cb@users.noreply.github.com>
Date: Wed, 28 Aug 2024 10:45:05 +0200
Subject: [PATCH] cloudwatch_metric_alarm: fix idempotency for alarm without
 dimensions (#1865)

SUMMARY
A metric alarm in Cloudwatch can optionally have Dimensions. When a metric alarm in Cloudwatch does not have any dimensions, it returns: "Dimensions": [] when queried via boto3.
When configuring a metric alarm without Dimensions in Cloudwatch using the cloudwatch_metric_alarm plugin, Dimensions must be absent from the parameters.
Because "Dimensions": [] does not match Dimensions: None, the result is always Changed.
This Pull Request fixes this by setting Dimensions from the returned alarm parameters to None when the field is empty.
Fixes #1750
ISSUE TYPE

Bugfix Pull Request

COMPONENT NAME
cloudwatch_metric_alarm
ADDITIONAL INFORMATION

Reviewed-by: GomathiselviS
Reviewed-by: Jasper Misset
Reviewed-by: Alina Buzachis
Reviewed-by: Mark Chappell
---
 ...16-cloudwatch-metric-alarm-idempotency.yml |  3 ++
 plugins/modules/cloudwatch_metric_alarm.py    |  4 ++
 .../cloudwatch_metric_alarm/tasks/main.yml    | 51 +++++++++++++++++++
 3 files changed, 58 insertions(+)
 create mode 100644 changelogs/fragments/20240216-cloudwatch-metric-alarm-idempotency.yml

diff --git a/changelogs/fragments/20240216-cloudwatch-metric-alarm-idempotency.yml b/changelogs/fragments/20240216-cloudwatch-metric-alarm-idempotency.yml
new file mode 100644
index 00000000000..bd31947942e
--- /dev/null
+++ b/changelogs/fragments/20240216-cloudwatch-metric-alarm-idempotency.yml
@@ -0,0 +1,3 @@
+---
+bugfixes:
+  - cloudwatch_metric_alarm - Fix idempotency when creating cloudwatch metric alarm without dimensions (https://github.com/ansible-collections/amazon.aws/pull/1865).
\ No newline at end of file
diff --git a/plugins/modules/cloudwatch_metric_alarm.py b/plugins/modules/cloudwatch_metric_alarm.py
index f412e94e548..00c47a319f5 100644
--- a/plugins/modules/cloudwatch_metric_alarm.py
+++ b/plugins/modules/cloudwatch_metric_alarm.py
@@ -467,6 +467,10 @@ def create_metric_alarm(connection, module, params):
         if "TreatMissingData" not in alarm.keys():
             alarm["TreatMissingData"] = "missing"
 
+        # Prevent alarm without dimensions to always return changed
+        if not alarm["Dimensions"]:
+            alarm.pop("Dimensions", None)
+
         # Exclude certain props from change detection
         for key in [
             "ActionsEnabled",
diff --git a/tests/integration/targets/cloudwatch_metric_alarm/tasks/main.yml b/tests/integration/targets/cloudwatch_metric_alarm/tasks/main.yml
index 439a1c000bd..5cf9dda6324 100644
--- a/tests/integration/targets/cloudwatch_metric_alarm/tasks/main.yml
+++ b/tests/integration/targets/cloudwatch_metric_alarm/tasks/main.yml
@@ -509,6 +509,57 @@
           - ec2_instance_metric_mutually_exclusive.failed
           - '"parameters are mutually exclusive" in ec2_instance_metric_mutually_exclusive.msg'
 
+    - name: create alarm without dimensions
+      cloudwatch_metric_alarm:
+        state: present
+        name: '{{ alarm_full_name }}'
+        metric: CPUUtilization
+        namespace: AWS/EC2
+        treat_missing_data: missing
+        statistic: Average
+        comparison: LessThanOrEqualToThreshold
+        threshold: 5.0
+        period: 300
+        evaluation_periods: 3
+        unit: Percent
+        description: This will alarm when an instance's cpu usage average is lower than
+          5% for 15 minutes
+      register: ec2_instance_metric_alarm_no_dimensions
+
+    - name: get info on alarm without dimensions
+      amazon.aws.cloudwatch_metric_alarm_info:
+        alarm_names:
+          - "{{ alarm_full_name }}"
+      register: alarm_info_metrics_alarm_no_dimensions
+
+    - name: verify that an alarm was created without dimensions
+      ansible.builtin.assert:
+        that:
+          - ec2_instance_metric_alarm_no_dimensions.changed
+          - alarm_info_metrics_alarm_no_dimensions.metric_alarms[0].dimensions | length == 0
+
+    - name: create alarm without dimensions (idempotent)
+      cloudwatch_metric_alarm:
+        state: present
+        name: '{{ alarm_full_name }}'
+        metric: CPUUtilization
+        namespace: AWS/EC2
+        treat_missing_data: missing
+        statistic: Average
+        comparison: LessThanOrEqualToThreshold
+        threshold: 5.0
+        period: 300
+        evaluation_periods: 3
+        unit: Percent
+        description: This will alarm when an instance's cpu usage average is lower than
+          5% for 15 minutes
+      register: ec2_instance_metric_alarm_no_dimensions_idempotent
+
+    - name: "Verify alarm without dimensions does not register as changed after update"
+      assert:
+        that:
+          - not ec2_instance_metric_alarm_no_dimensions_idempotent.changed
+
   always:
     - name: try to delete the alarm
       amazon.aws.cloudwatch_metric_alarm: