Setup Lambda to trigger from CloudWatch using CloudFormation - amazon-web-services

Question

I want to use CloudFormation to trigger Lambda when my CloudWatch function is called. I have the below, but it does not work.
CloudWatch rule created fine
"CloudWatchNewEc2": {
"Type": "AWS::Events::Rule",
"DependsOn": ["LambdaNewEc2"],
"Properties": {
"Description": "Triggered on new EC2 instances",
"EventPattern": {
"source": [
"aws.ec2"
],
"detail-type": [
"AWS API Call via CloudTrail"
],
"detail": {
"eventSource": [
"ec2.amazonaws.com"
],
"eventName": [
"RunInstances"
]
}
},
"Targets": [
{
"Arn": {
"Fn::GetAtt": ["LambdaNewEc2", "Arn"]
},
"Id": "NewEc2AutoTag"
}
]
}
},
Lambda created but is not triggered
"LambdaNewEc2": {
"Type": "AWS::Lambda::Function",
"DependsOn": ["S3Lambda", "IAMRoleLambda"],
"Properties": {
"Code": {
"S3Bucket": {"Ref": "LambdaBucketName"},
"S3Key": "skynet-lambda.zip"
},
"Description": "When new EC2 instances are created, auto tag them",
"FunctionName": "newEc2AutoTag",
"Handler": "index.newEc2_autoTag",
"Role": {"Fn::GetAtt": ["IAMRoleLambda", "Arn"]},
"Runtime": "nodejs6.10",
"Timeout": "30"
}
}
},
It seems like CloudWatch Target is not sufficient?
UPDATE (Full CloudFormation template)
{
"Parameters": {
"Environment": {
"Type": "String",
"Default": "Staging",
"AllowedValues": [
"Testing",
"Staging",
"Production"
],
"Description": "Environment name"
},
"BucketName": {
"Type": "String",
"Default": "skynet-staging",
"Description": "Bucket Name"
},
"LambdaBucketName": {
"Type": "String",
"Default": "skynet-lambda",
"Description": "Lambda Bucket Name"
},
"Owner": {
"Type": "String",
"Description": "Owner"
}
},
"Resources": {
"S3Web": {
"Type": "AWS::S3::Bucket",
"Properties": {
"BucketName": {
"Ref": "BucketName"
},
"WebsiteConfiguration": {
"IndexDocument": "index.html",
"RoutingRules": [
{
"RedirectRule": {
"ReplaceKeyPrefixWith": "#"
},
"RoutingRuleCondition": {
"HttpErrorCodeReturnedEquals": "404"
}
}
]
},
"AccessControl": "PublicRead",
"Tags": [
{
"Key": "Cost Center",
"Value": "Skynet"
},
{
"Key": "Environment",
"Value": {
"Ref": "Environment"
}
},
{
"Key": "Owner",
"Value": {
"Ref": "Owner"
}
}
]
}
},
"S3Lambda": {
"Type": "AWS::S3::Bucket",
"Properties": {
"BucketName": {
"Ref": "LambdaBucketName"
},
"VersioningConfiguration": {
"Status": "Enabled"
},
"Tags": [
{
"Key": "Cost Center",
"Value": "Skynet"
},
{
"Key": "Owner",
"Value": {
"Ref": "Owner"
}
}
]
}
},
"CloudWatchNewEc2": {
"Type": "AWS::Events::Rule",
"DependsOn": ["LambdaNewEc2"],
"Properties": {
"Description": "Triggered on new EC2 instances",
"EventPattern": {
"source": [
"aws.ec2"
],
"detail-type": [
"AWS API Call via CloudTrail"
],
"detail": {
"eventSource": [
"ec2.amazonaws.com"
],
"eventName": [
"RunInstances"
]
}
},
"Targets": [
{
"Arn": {
"Fn::GetAtt": ["LambdaNewEc2", "Arn"]
},
"Id": "NewEc2AutoTag"
}
]
}
},
"IAMRoleLambda": {
"Type": "AWS::IAM::Role",
"Properties": {
"RoleName": "skynet-lambda-role",
"AssumeRolePolicyDocument": {
"Version" : "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Principal": {
"Service": [ "lambda.amazonaws.com" ]
},
"Action": [ "sts:AssumeRole" ]
}
]
},
"ManagedPolicyArns": [
"arn:aws:iam::aws:policy/AmazonEC2FullAccess",
"arn:aws:iam::aws:policy/AWSLambdaFullAccess",
"arn:aws:iam::aws:policy/AWSXrayWriteOnlyAccess",
"arn:aws:iam::aws:policy/CloudWatchLogsFullAccess"
]
}
},
"LambdaNewEc2": {
"Type": "AWS::Lambda::Function",
"DependsOn": ["S3Lambda", "IAMRoleLambda"],
"Properties": {
"Code": {
"S3Bucket": {"Ref": "LambdaBucketName"},
"S3Key": "skynet-lambda.zip"
},
"Description": "When new EC2 instances are created, auto tag them",
"FunctionName": "newEc2AutoTag",
"Handler": "index.newEc2_autoTag",
"Role": {"Fn::GetAtt": ["IAMRoleLambda", "Arn"]},
"Runtime": "nodejs6.10",
"Timeout": "30"
}
}
},
"Outputs": {
"WebUrl": {
"Value": {
"Fn::GetAtt": [
"S3Web",
"WebsiteURL"
]
},
"Description": "S3 bucket for web files"
}
}
}

Answer 1

I managed to deploy your template into a CloudFormation stack (by removing the LambdaBucket and pointing to my own zip file). It seems to create all resource correctly.
It took about 10 minutes for the RunInstances event to appear in CloudTrail. It then successfully triggered the Rule, but the CloudWatch metrics for my rule showed a failed invocation because I faked a Lambda function for your template.
Once I edited the rule to point to a better function and re-tested, it worked fine.
Bottom line: Seems to work!