Support for CloudWatch Metric Math Alarms

index.js

@@ -3,6 +3,7 @@ var url = require('url');
 var https = require('https');
 var config = require('./config');
 var _ = require('lodash');
+var escapeStringRegexp = require('escape-string-regexp');
 var hookUrl;
 
 var baseSlackMessage = {}
@@ -233,12 +234,31 @@ 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 trigger = message.Trigger;
+  var alarmExpression;
+
+  if (typeof trigger.Metrics === 'object') {
+    // This is a CloudWatch metric math alarm. Instead of a MetricName and
+    // statistic there is an array of Metrics where the first element is the
+    // math expression. Need to process each metric in the list of Metrics
+    // and replace occurences of it in the alarm expression
+    alarmExpression = trigger.Metrics[0].Expression;
+    var triggerMetricsLength = trigger.Metrics.length;
+    for (var i = 1; i < triggerMetricsLength; i++) {
+      var metric = trigger.Metrics[i];
+      alarmExpression = alarmExpression.replace(
+        new RegExp(escapeStringRegexp(metric.Id), 'g'),
+        metric.MetricStat.Stat + ':' + metric.MetricStat.Metric.MetricName
+      );
+    }
+  } else {
+    // This is a standard CloudWatch alarm on a single metric
+    alarmExpression = trigger.Statistic + ":" + trigger.MetricName;
+  }
   var oldState = message.OldStateValue;
   var newState = message.NewStateValue;
   var alarmDescription = message.AlarmDescription;
   var alarmReason = message.NewStateReason;
-  var trigger = message.Trigger;
   var color = "warning";
 
   if (message.NewStateValue === "ALARM") {
@@ -257,8 +277,7 @@ var handleCloudWatch = function(event, context) {
           { "title": "Alarm Description", "value": alarmDescription, "short": false},
           {
             "title": "Trigger",
-            "value": trigger.Statistic + " "
-              + metricName + " "
+            "value": alarmExpression + " "
               + trigger.ComparisonOperator + " "
               + trigger.Threshold + " for "
               + trigger.EvaluationPeriods + " period(s) of "
@@ -364,7 +383,7 @@ var processEvent = function(event, context) {
   try {
     eventSnsMessage = JSON.parse(eventSnsMessageRaw);
   }
-  catch (e) {    
+  catch (e) {
   }
 
   if(eventSubscriptionArn.indexOf(config.services.codepipeline.match_text) > -1 || eventSnsSubject.indexOf(config.services.codepipeline.match_text) > -1 || eventSnsMessageRaw.indexOf(config.services.codepipeline.match_text) > -1){

package.json

@@ -2,7 +2,7 @@
   "name": "lambda-cloudwatch-slack",
   "version": "0.3.0",
   "description": "Better Slack notifications for AWS CloudWatch",
-  "authors": [    
+  "authors": [
     "Christopher Reichert <creichert07@gmail.com>",
     "Cody Reichert <codyreichert@gmail.com>",
     "Alexandr Promakh <s-promakh@ya.ru>"
@@ -12,6 +12,7 @@
   },
   "dependencies": {
     "aws-sdk": "^2.4.0",
+    "escape-string-regexp": "^2.0.0",
     "https": "^1.0.0",
     "lodash": "^4.15.0",
     "url": "^0.11.0"

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-event-metricmath.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
+$NODE_LAMBDA run -x test/context.json -j test/sns-autoscaling-event.json

test/sns-cloudwatch-event-metricmath.json

@@ -0,0 +1,18 @@
+{
+    "Records": [
+        {
+            "EventSource": "aws:sns",
+            "EventVersion": "1.0",
+            "EventSubscriptionArn": "arn:aws:sns:us-east-1:123456789123:cloudwatch-alarms:00000000-0000-0000-0000-000000000000",
+            "Sns": {
+                "Type": "Notification",
+                "MessageId": "00000000-0000-0000-0000-000000000000",
+                "TopicArn": "arn:aws:sns:us-east-1:123456789123:cloudwatch-alarms",
+                "Subject": "ALARM: \"Sample Metric Math Alert\" in US East (N. Virginia)",
+                "Message": "{\"AlarmName\":\"Sample Metric Math Alert\",\"AlarmDescription\":null,\"AWSAccountId\":\"946184294613\",\"NewStateValue\":\"ALARM\",\"NewStateReason\":\"Threshold Crossed: 1 out of the last 1 datapoints [8133.333333333447 (07/08/19 18:43:00)] was greater than the threshold (1000.0) (minimum 1 datapoint for OK -> ALARM transition).\",\"StateChangeTime\":\"2019-08-07T18:45:24.269+0000\",\"Region\":\"US East (N. Virginia)\",\"OldStateValue\":\"OK\",\"Trigger\":{\"Period\":60,\"EvaluationPeriods\":1,\"ComparisonOperator\":\"GreaterThanThreshold\",\"Threshold\":1000.0,\"TreatMissingData\":\"- TreatMissingData:                    missing\",\"EvaluateLowSampleCountPercentile\":\"\",\"Metrics\":[{\"Expression\":\"m1*100*m2 - MIN(m1)\",\"Id\":\"e2\",\"Label\":\"Expression2\",\"ReturnData\":true},{\"Id\":\"m1\",\"MetricStat\":{\"Metric\":{\"Dimensions\":[{\"value\":\"i-0a5c8ea70646e7b05\",\"name\":\"InstanceId\"}],\"MetricName\":\"CPUUtilization\",\"Namespace\":\"AWS/EC2\"},\"Period\":60,\"Stat\":\"Average\"},\"ReturnData\":false},{\"Id\":\"m2\",\"MetricStat\":{\"Metric\":{\"Dimensions\":[{\"value\":\"i-0a5c8ea70646e7b05\",\"name\":\"InstanceId\"}],\"MetricName\":\"NetworkOut\",\"Namespace\":\"AWS/EC2\"},\"Period\":60,\"Stat\":\"Average\"},\"ReturnData\":false}]}}",
+                "Timestamp": "2019-08-07T18:45:24.355Z",
+                "MessageAttributes": {}
+            }
+        }
+    ]
+}