Fix : Added implementation for CloudWatch Describe Metric for Alarm (#3148)

* Fix : added implementation for CloudWatch Describe Metric for Alarm

* Linting

Co-authored-by: Bert Blommers <info@bertblommers.nl>

moto/cloudwatch/responses.py

@@ -161,9 +161,23 @@ class CloudWatchResponse(BaseResponse):
     def describe_alarm_history(self):
         raise NotImplementedError()
 
+    @staticmethod
+    def filter_alarms(alarms, metric_name, namespace):
+        metric_filtered_alarms = []
+
+        for alarm in alarms:
+            if alarm.metric_name == metric_name and alarm.namespace == namespace:
+                metric_filtered_alarms.append(alarm)
+        return metric_filtered_alarms
+
     @amzn_request_id
     def describe_alarms_for_metric(self):
-        raise NotImplementedError()
+        alarms = self.cloudwatch_backend.get_all_alarms()
+        namespace = self._get_param("Namespace")
+        metric_name = self._get_param("MetricName")
+        filtered_alarms = self.filter_alarms(alarms, metric_name, namespace)
+        template = self.response_template(DESCRIBE_METRIC_ALARMS_TEMPLATE)
+        return template.render(alarms=filtered_alarms)
 
     @amzn_request_id
     def disable_alarm_actions(self):
@@ -282,6 +296,57 @@ DESCRIBE_ALARMS_TEMPLATE = """<DescribeAlarmsResponse xmlns="http://monitoring.a
     </DescribeAlarmsResult>
 </DescribeAlarmsResponse>"""
 
+DESCRIBE_METRIC_ALARMS_TEMPLATE = """<DescribeAlarmsForMetricResponse xmlns="http://monitoring.amazonaws.com/doc/2010-08-01/">
+    <DescribeAlarmsForMetricResult>
+        <MetricAlarms>
+            {% for alarm in alarms %}
+            <member>
+                <ActionsEnabled>{{ alarm.actions_enabled }}</ActionsEnabled>
+                <AlarmActions>
+                    {% for action in alarm.alarm_actions %}
+                    <member>{{ action }}</member>
+                    {% endfor %}
+                </AlarmActions>
+                <AlarmArn>{{ alarm.arn }}</AlarmArn>
+                <AlarmConfigurationUpdatedTimestamp>{{ alarm.configuration_updated_timestamp }}</AlarmConfigurationUpdatedTimestamp>
+                <AlarmDescription>{{ alarm.description }}</AlarmDescription>
+                <AlarmName>{{ alarm.name }}</AlarmName>
+                <ComparisonOperator>{{ alarm.comparison_operator }}</ComparisonOperator>
+                <Dimensions>
+                    {% for dimension in alarm.dimensions %}
+                    <member>
+                        <Name>{{ dimension.name }}</Name>
+                        <Value>{{ dimension.value }}</Value>
+                    </member>
+                    {% endfor %}
+                </Dimensions>
+                <EvaluationPeriods>{{ alarm.evaluation_periods }}</EvaluationPeriods>
+                <InsufficientDataActions>
+                    {% for action in alarm.insufficient_data_actions %}
+                    <member>{{ action }}</member>
+                    {% endfor %}
+                </InsufficientDataActions>
+                <MetricName>{{ alarm.metric_name }}</MetricName>
+                <Namespace>{{ alarm.namespace }}</Namespace>
+                <OKActions>
+                    {% for action in alarm.ok_actions %}
+                    <member>{{ action }}</member>
+                    {% endfor %}
+                </OKActions>
+                <Period>{{ alarm.period }}</Period>
+                <StateReason>{{ alarm.state_reason }}</StateReason>
+                <StateReasonData>{{ alarm.state_reason_data }}</StateReasonData>
+                <StateUpdatedTimestamp>{{ alarm.state_updated_timestamp }}</StateUpdatedTimestamp>
+                <StateValue>{{ alarm.state_value }}</StateValue>
+                <Statistic>{{ alarm.statistic }}</Statistic>
+                <Threshold>{{ alarm.threshold }}</Threshold>
+                <Unit>{{ alarm.unit }}</Unit>
+            </member>
+            {% endfor %}
+        </MetricAlarms>
+    </DescribeAlarmsForMetricResult>
+</DescribeAlarmsForMetricResponse>"""
+
 DELETE_METRIC_ALARMS_TEMPLATE = """<DeleteMetricAlarmResponse xmlns="http://monitoring.amazonaws.com/doc/2010-08-01/">
    <ResponseMetadata>
       <RequestId>

tests/test_cloudwatch/test_cloudwatch.py

@@ -127,6 +127,22 @@ def test_describe_alarms():
     alarms.should.have.length_of(0)
 
 
+@mock_cloudwatch_deprecated
+def test_describe_alarms_for_metric():
+    conn = boto.connect_cloudwatch()
+
+    conn.create_alarm(alarm_fixture(name="nfoobar", action="afoobar"))
+    conn.create_alarm(alarm_fixture(name="nfoobaz", action="afoobaz"))
+    conn.create_alarm(alarm_fixture(name="nbarfoo", action="abarfoo"))
+    conn.create_alarm(alarm_fixture(name="nbazfoo", action="abazfoo"))
+
+    alarms = conn.describe_alarms_for_metric("nbarfoo_metric", "nbarfoo_namespace")
+    alarms.should.have.length_of(1)
+
+    alarms = conn.describe_alarms_for_metric("nbazfoo_metric", "nbazfoo_namespace")
+    alarms.should.have.length_of(1)
+
+
 @mock_cloudwatch_deprecated
 def test_get_metric_statistics():
     conn = boto.connect_cloudwatch()

tests/test_cloudwatch/test_cloudwatch_boto3.py

@@ -123,6 +123,24 @@ def test_delete_invalid_alarm():
     e.exception.response["Error"]["Code"].should.equal("ResourceNotFound")
 
 
+@mock_cloudwatch
+def test_describe_alarms_for_metric():
+    conn = boto3.client("cloudwatch", region_name="eu-central-1")
+    conn.put_metric_alarm(
+        AlarmName="testalarm1",
+        MetricName="cpu",
+        Namespace="blah",
+        Period=10,
+        EvaluationPeriods=5,
+        Statistic="Average",
+        Threshold=2,
+        ComparisonOperator="GreaterThanThreshold",
+        ActionsEnabled=True,
+    )
+    alarms = conn.describe_alarms_for_metric(MetricName="cpu", Namespace="blah")
+    alarms.get("MetricAlarms").should.have.length_of(1)
+
+
 @mock_cloudwatch
 def test_alarm_state():
     client = boto3.client("cloudwatch", region_name="eu-central-1")