Unfortunately, the official AWS::CloudFormation template only allows you to control Amazon S3 NotificationConfiguration as a NotificationConfiguration property of the parent AWS::S3::Bucket Resource, which means that you can't attach this configuration to any existing bucket, you have to apply it to a CloudFormation-managed bucket for it to work.
A workaround is to implement the PUT Bucket Notification API call directly as a Lambda-backed Custom Resource using the putBucketNotificationConfiguration JavaScript API call. However, because modifying the NotificationConfiguration on S3 buckets is restricted to the bucket's creator, you also need to add an AWS::S3::BucketPolicy Resource granting your Lambda Function access to the s3:PutBucketNotification action.
Here's a complete, self-contained CloudFormation template that demonstrates how to trigger a Lambda function whenever a file is added to an existing S3 bucket, using 2 Lambda-Backed Custom Resources (BucketConfiguration to set the bucket notification configuration, S3Object to upload an object to the bucket) and a third Lambda function (BucketWatcher to trigger the Wait Condition when an object is uploaded to the bucket).
Description: Upload an object to an S3 bucket, triggering a Lambda event, returning the object key as a Stack Output.
Parameters:
Key:
Description: S3 Object key
Type: String
Default: test
Body:
Description: S3 Object body content
Type: String
Default: TEST CONTENT
BucketName:
Description: S3 Bucket name (must already exist)
Type: String
Resources:
BucketConfiguration:
Type: Custom::S3BucketConfiguration
DependsOn:
- BucketPermission
- NotificationBucketPolicy
Properties:
ServiceToken: !GetAtt S3BucketConfiguration.Arn
Bucket: !Ref BucketName
NotificationConfiguration:
LambdaFunctionConfigurations:
- Events: ['s3:ObjectCreated:*']
LambdaFunctionArn: !GetAtt BucketWatcher.Arn
S3BucketConfiguration:
Type: AWS::Lambda::Function
Properties:
Description: S3 Object Custom Resource
Handler: index.handler
Role: !GetAtt LambdaExecutionRole.Arn
Code:
ZipFile: !Sub |
var response = require('cfn-response');
var AWS = require('aws-sdk');
var s3 = new AWS.S3();
exports.handler = function(event, context) {
var respond = (e) => response.send(event, context, e ? response.FAILED : response.SUCCESS, e ? e : {});
process.on('uncaughtException', e=>failed(e));
var params = event.ResourceProperties;
delete params.ServiceToken;
if (event.RequestType === 'Delete') {
params.NotificationConfiguration = {};
s3.putBucketNotificationConfiguration(params).promise()
.then((data)=>respond())
.catch((e)=>respond());
} else {
s3.putBucketNotificationConfiguration(params).promise()
.then((data)=>respond())
.catch((e)=>respond(e));
}
};
Timeout: 30
Runtime: nodejs4.3
BucketPermission:
Type: AWS::Lambda::Permission
Properties:
Action: 'lambda:InvokeFunction'
FunctionName: !Ref BucketWatcher
Principal: s3.amazonaws.com
SourceAccount: !Ref "AWS::AccountId"
SourceArn: !Sub "arn:aws:s3:::${BucketName}"
BucketWatcher:
Type: AWS::Lambda::Function
Properties:
Description: Sends a Wait Condition signal to Handle when invoked
Handler: index.handler
Role: !GetAtt LambdaExecutionRole.Arn
Code:
ZipFile: !Sub |
exports.handler = function(event, context) {
console.log("Request received:\n", JSON.stringify(event));
var responseBody = JSON.stringify({
"Status" : "SUCCESS",
"UniqueId" : "Key",
"Data" : event.Records[0].s3.object.key,
"Reason" : ""
});
var https = require("https");
var url = require("url");
var parsedUrl = url.parse('${Handle}');
var options = {
hostname: parsedUrl.hostname,
port: 443,
path: parsedUrl.path,
method: "PUT",
headers: {
"content-type": "",
"content-length": responseBody.length
}
};
var request = https.request(options, function(response) {
console.log("Status code: " + response.statusCode);
console.log("Status message: " + response.statusMessage);
context.done();
});
request.on("error", function(error) {
console.log("send(..) failed executing https.request(..): " + error);
context.done();
});
request.write(responseBody);
request.end();
};
Timeout: 30
Runtime: nodejs4.3
Handle:
Type: AWS::CloudFormation::WaitConditionHandle
Wait:
Type: AWS::CloudFormation::WaitCondition
Properties:
Handle: !Ref Handle
Timeout: 300
S3Object:
Type: Custom::S3Object
DependsOn: BucketConfiguration
Properties:
ServiceToken: !GetAtt S3ObjectFunction.Arn
Bucket: !Ref BucketName
Key: !Ref Key
Body: !Ref Body
S3ObjectFunction:
Type: AWS::Lambda::Function
Properties:
Description: S3 Object Custom Resource
Handler: index.handler
Role: !GetAtt LambdaExecutionRole.Arn
Code:
ZipFile: !Sub |
var response = require('cfn-response');
var AWS = require('aws-sdk');
var s3 = new AWS.S3();
exports.handler = function(event, context) {
var respond = (e) => response.send(event, context, e ? response.FAILED : response.SUCCESS, e ? e : {});
var params = event.ResourceProperties;
delete params.ServiceToken;
if (event.RequestType == 'Create' || event.RequestType == 'Update') {
s3.putObject(params).promise()
.then((data)=>respond())
.catch((e)=>respond(e));
} else if (event.RequestType == 'Delete') {
delete params.Body;
s3.deleteObject(params).promise()
.then((data)=>respond())
.catch((e)=>respond(e));
} else {
respond({Error: 'Invalid request type'});
}
};
Timeout: 30
Runtime: nodejs4.3
LambdaExecutionRole:
Type: AWS::IAM::Role
Properties:
AssumeRolePolicyDocument:
Version: '2012-10-17'
Statement:
- Effect: Allow
Principal: {Service: [lambda.amazonaws.com]}
Action: ['sts:AssumeRole']
Path: /
ManagedPolicyArns:
- "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
Policies:
- PolicyName: S3Policy
PolicyDocument:
Version: '2012-10-17'
Statement:
- Effect: Allow
Action:
- 's3:PutObject'
- 'S3:DeleteObject'
Resource: !Sub "arn:aws:s3:::${BucketName}/${Key}"
NotificationBucketPolicy:
Type: AWS::S3::BucketPolicy
Properties:
Bucket: !Ref BucketName
PolicyDocument:
Statement:
- Effect: "Allow"
Action:
- 's3:PutBucketNotification'
Resource: !Sub "arn:aws:s3:::${BucketName}"
Principal:
AWS: !GetAtt LambdaExecutionRole.Arn
Outputs:
Result:
Value: !GetAtt Wait.Data
