From e04ea6163932f6fdd523a5d6c679703e97071596 Mon Sep 17 00:00:00 2001
From: Alexander Girke <alexander.girke@thing-it.com>
Date: Thu, 17 Mar 2022 12:46:15 +0100
Subject: [PATCH] Add support for Cloudwatch Composite Alarms

---
 index.js                                 | 17 ++++++-----------
 scripts/test.sh                          |  3 ++-
 test/sns-cloudwatch-composite-event.json | 18 ++++++++++++++++++
 3 files changed, 26 insertions(+), 12 deletions(-)
 create mode 100644 test/sns-cloudwatch-composite-event.json

diff --git a/index.js b/index.js
index c61ab4e6..3ac66fa6 100644
--- a/index.js
+++ b/index.js
@@ -233,12 +233,12 @@ var handleCloudWatch = function(event, context) {
   var region = event.Records[0].EventSubscriptionArn.split(":")[3];
   var subject = "AWS CloudWatch Notification";
   var alarmName = message.AlarmName;
-  var metricName = message.Trigger.MetricName;
   var oldState = message.OldStateValue;
   var newState = message.NewStateValue;
   var alarmDescription = message.AlarmDescription;
   var alarmReason = message.NewStateReason;
   var trigger = message.Trigger;
+  var triggeringChildren = message.TriggeringChildren || [] // for composite alarms
   var color = "warning";
 
   if (message.NewStateValue === "ALARM") {
@@ -247,6 +247,10 @@ var handleCloudWatch = function(event, context) {
       color = "good";
   }
 
+  var triggerMessage = trigger
+      ? `${trigger.Statistic} ${trigger.MetricName} ${trigger.ComparisonOperator} ${trigger.Threshold} for ${trigger.EvaluationPeriods} period(s) of ${trigger.Period} seconds.`
+      : triggeringChildren.map(it => it.Arn).join(" and ") + " transitioned to ALARM state."
+
   var slackMessage = {
     text: "*" + subject + "*",
     attachments: [
@@ -255,16 +259,7 @@ var handleCloudWatch = function(event, context) {
         "fields": [
           { "title": "Alarm Name", "value": alarmName, "short": true },
           { "title": "Alarm Description", "value": alarmDescription, "short": false},
-          {
-            "title": "Trigger",
-            "value": trigger.Statistic + " "
-              + metricName + " "
-              + trigger.ComparisonOperator + " "
-              + trigger.Threshold + " for "
-              + trigger.EvaluationPeriods + " period(s) of "
-              + trigger.Period + " seconds.",
-              "short": false
-          },
+          { "title": "Trigger", "value": triggerMessage, "short": false },
           { "title": "Old State", "value": oldState, "short": true },
           { "title": "Current State", "value": newState, "short": true },
           {
diff --git a/scripts/test.sh b/scripts/test.sh
index c3e1b273..1873e3aa 100755
--- a/scripts/test.sh
+++ b/scripts/test.sh
@@ -5,9 +5,10 @@ $NODE_LAMBDA run -x test/context.json -j test/sns-codepipeline-event-stage-start
 $NODE_LAMBDA run -x test/context.json -j test/sns-codepipeline-event-stage-succeeded.json
 $NODE_LAMBDA run -x test/context.json -j test/sns-codepipeline-event-stage-failed.json
 $NODE_LAMBDA run -x test/context.json -j test/sns-cloudwatch-event.json
+$NODE_LAMBDA run -x test/context.json -j test/sns-cloudwatch-composite-event.json
 $NODE_LAMBDA run -x test/context.json -j test/sns-event.json
 $NODE_LAMBDA run -x test/context.json -j test/sns-elastic-beanstalk-event.json
 $NODE_LAMBDA run -x test/context.json -j test/sns-codedeploy-event.json
 $NODE_LAMBDA run -x test/context.json -j test/sns-codedeploy-configuration.json
 $NODE_LAMBDA run -x test/context.json -j test/sns-elasticache-event.json
-$NODE_LAMBDA run -x test/context.json -j test/sns-autoscaling-event.json
\ No newline at end of file
+$NODE_LAMBDA run -x test/context.json -j test/sns-autoscaling-event.json
diff --git a/test/sns-cloudwatch-composite-event.json b/test/sns-cloudwatch-composite-event.json
new file mode 100644
index 00000000..49db505b
--- /dev/null
+++ b/test/sns-cloudwatch-composite-event.json
@@ -0,0 +1,18 @@
+{
+  "Records": [
+    {
+      "EventSource": "aws:sns",
+      "EventVersion": "1.0",
+      "EventSubscriptionArn": "arn:aws:sns:us-west-2:123456789123:CloudWatchNotifications:00000000-0000-0000-0000-000000000000",
+      "Sns": {
+        "Type": "Notification",
+        "MessageId": "82728d9c-3a57-5c0f-b8f6-d730c5b86ba4",
+        "TopicArn": "arn:aws:sns:us-west-2:123456789123:CloudWatchNotifications",
+        "Timestamp": "2022-03-17T09:21:51.857Z",
+        "Subject": "ALARM: \"composite-alarm\" in US West - Oregon",
+        "Message": "{\"AlarmName\":\"composite-alarm\",\"AlarmDescription\":\"A composite alarm.\",\"AWSAccountId\":\"123456789123\",\"NewStateValue\":\"ALARM\",\"NewStateReason\":\"arn:aws:cloudwatch:us-west-2:123456789123:alarm:Alarm1 transitioned to ALARM at Thursday 17 March, 2022 09:21:51 UTC\",\"StateChangeTime\":\"2022-03-17T09:21:51.792+0000\",\"Region\":\"US West - Oregon\",\"AlarmArn\":\"arn:aws:cloudwatch:us-west-2:123456789123:alarm:composite-alarm\",\"OKActions\":[\"arn:aws:sns:us-west-2:123456789123:topic\"],\"AlarmActions\":[\"arn:aws:sns:us-west-2:123456789123:topic\"],\"InsufficientDataActions\":[],\"OldStateValue\":\"OK\",\"AlarmRule\":\"ALARM(\\\"Alarm1\\\") AND ALARM(\\\"Alarm2\\\")\",\"TriggeringChildren\":[{\"Arn\":\"arn:aws:cloudwatch:us-west-2:123456789123:alarm:Alarm1\",\"State\":{\"Value\":\"ALARM\",\"Timestamp\":\"2022-03-17T09:21:51.792+0000\"}},{\"Arn\":\"arn:aws:cloudwatch:us-west-2:123456789123:alarm:Alarm2\",\"State\":{\"Value\":\"ALARM\",\"Timestamp\":\"2022-03-17T09:21:37.874+0000\"}}]}",
+        "MessageAttributes": {}
+      }
+    }
+  ]
+}