AWS Lambda Function Code

Code is a property of the AWS::Lambda::Function resource that specifies the code for a Lambda function. For all runtimes, you can specify the location of a deployment package in Amazon S3. For Node.js and Python functions, you can also specify the function code inline in the template.

Syntax

{
  "S3Bucket" : String,
  "S3Key" : String,
  "S3ObjectVersion" : String,
  "ZipFile" : String
}

S3Bucket: String
S3Key: String
S3ObjectVersion: String
ZipFile: String

Properties

cfn-response Module

When you use the ZipFile property to specify your function's source code and that function interacts with an AWS CloudFormation custom resource, you can load the cfn-response module to send responses to those resources. The module contains a send method, which sends a response object to a custom resource by way of an Amazon S3 presigned URL (the ResponseURL).

After executing the send method, the Lambda function terminates, so anything you write after that method is ignored.

Loading the cfn-response Module

For Node.js functions, use the require() function to load the cfn-response module. For example, the following code example creates a cfn-response object with the name response:

var response = require('cfn-response');

For Python, use the import statement to load the cfnresponse module, as shown in the following example:

import cfnresponse

send Method Parameters

You can use the following parameters with the send method.

Examples

Node.js

In the following Node.js example, the inline Lambda function takes an input value and multiplies it by 5. Inline functions are especially useful for smaller functions because they allow you to specify the source code directly in the template, instead of creating a package and uploading it to an Amazon S3 bucket. The function uses the cfn-response send method to send the result back to the custom resource that invoked it.

"ZipFile": { "Fn::Join": ["", [
  "var response = require('cfn-response');",
  "exports.handler = function(event, context) {",
  "  var input = parseInt(event.ResourceProperties.Input);",
  "  var responseData = {Value: input * 5};",
  "  response.send(event, context, response.SUCCESS, responseData);",
  "};"
]]}

ZipFile: >
  var response = require('cfn-response');
  exports.handler = function(event, context) {
    var input = parseInt(event.ResourceProperties.Input);
    var responseData = {Value: input * 5};
    response.send(event, context, response.SUCCESS, responseData);
  };

Python

In the following Python example, the inline Lambda function takes an integer value and multiplies it by 5.

"ZipFile" : { "Fn::Join" : ["\n", [
  "import json",
  "import cfnresponse",
  "def handler(event, context):",
  "   responseValue = int(event['ResourceProperties']['Input']) * 5",
  "   responseData = {}",
  "   responseData['Data'] = responseValue",
  "   cfnresponse.send(event, context, cfnresponse.SUCCESS, responseData, \"CustomResourcePhysicalID\")"
]]}

ZipFile: |
  import json
  import cfnresponse
  def handler(event, context):
    responseValue = int(event['ResourceProperties']['Input']) * 5
    responseData = {}
    responseData['Data'] = responseValue
    cfnresponse.send(event, context, cfnresponse.SUCCESS, responseData, "CustomResourcePhysicalID")

Module Source Code

The following is the response module source code for the Node.js functions. Review it to understand what the module does and for help with implementing your own response functions.

/* Copyright 2015 Amazon Web Services, Inc. or its affiliates. All Rights Reserved.
   This file is licensed to you under the AWS Customer Agreement (the "License").
   You may not use this file except in compliance with the License.
   A copy of the License is located at http://aws.amazon.com/agreement/ .
   This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied.
   See the License for the specific language governing permissions and limitations under the License. */

exports.SUCCESS = "SUCCESS";
exports.FAILED = "FAILED";

exports.send = function(event, context, responseStatus, responseData, physicalResourceId, noEcho) {

    var responseBody = JSON.stringify({
        Status: responseStatus,
        Reason: "See the details in CloudWatch Log Stream: " + context.logStreamName,
        PhysicalResourceId: physicalResourceId || context.logStreamName,
        StackId: event.StackId,
        RequestId: event.RequestId,
        LogicalResourceId: event.LogicalResourceId,
        NoEcho: noEcho || false,
        Data: responseData
    });

    console.log("Response body:\n", responseBody);

    var https = require("https");
    var url = require("url");

    var parsedUrl = url.parse(event.ResponseURL);
    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();
}

The following is the response module source code for Python 3 functions:

#  Copyright 2016 Amazon Web Services, Inc. or its affiliates. All Rights Reserved.
#  This file is licensed to you under the AWS Customer Agreement (the "License").
#  You may not use this file except in compliance with the License.
#  A copy of the License is located at http://aws.amazon.com/agreement/ .
#  This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied.
#  See the License for the specific language governing permissions and limitations under the License.

from botocore.vendored import requests
import json

SUCCESS = "SUCCESS"
FAILED = "FAILED"

def send(event, context, responseStatus, responseData, physicalResourceId=None, noEcho=False):
    responseUrl = event['ResponseURL']

    print(responseUrl)

    responseBody = {}
    responseBody['Status'] = responseStatus
    responseBody['Reason'] = 'See the details in CloudWatch Log Stream: ' + context.log_stream_name
    responseBody['PhysicalResourceId'] = physicalResourceId or context.log_stream_name
    responseBody['StackId'] = event['StackId']
    responseBody['RequestId'] = event['RequestId']
    responseBody['LogicalResourceId'] = event['LogicalResourceId']
    responseBody['NoEcho'] = noEcho
    responseBody['Data'] = responseData

    json_responseBody = json.dumps(responseBody)

    print("Response body:\n" + json_responseBody)

    headers = {
        'content-type' : '',
        'content-length' : str(len(json_responseBody))
    }

    try:
        response = requests.put(responseUrl,
                                data=json_responseBody,
                                headers=headers)
        print("Status code: " + response.reason)
    except Exception as e:
        print("send(..) failed executing requests.put(..): " + str(e))

The following is the response module source code for Python 2 functions:

#  Copyright 2016 Amazon Web Services, Inc. or its affiliates. All Rights Reserved.
#  This file is licensed to you under the AWS Customer Agreement (the "License").
#  You may not use this file except in compliance with the License.
#  A copy of the License is located at http://aws.amazon.com/agreement/ .
#  This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied.
#  See the License for the specific language governing permissions and limitations under the License.

from botocore.vendored import requests
import json

SUCCESS = "SUCCESS"
FAILED = "FAILED"

def send(event, context, responseStatus, responseData, physicalResourceId=None, noEcho=False):
    responseUrl = event['ResponseURL']

    print responseUrl

    responseBody = {}
    responseBody['Status'] = responseStatus
    responseBody['Reason'] = 'See the details in CloudWatch Log Stream: ' + context.log_stream_name
    responseBody['PhysicalResourceId'] = physicalResourceId or context.log_stream_name
    responseBody['StackId'] = event['StackId']
    responseBody['RequestId'] = event['RequestId']
    responseBody['LogicalResourceId'] = event['LogicalResourceId']
    responseBody['NoEcho'] = noEcho
    responseBody['Data'] = responseData

    json_responseBody = json.dumps(responseBody)
   
    print "Response body:\n" + json_responseBody

    headers = {
        'content-type' : '', 
        'content-length' : str(len(json_responseBody))
    }
    
    try:
        response = requests.put(responseUrl,
                                data=json_responseBody,
                                headers=headers)
        print "Status code: " + response.reason
    except Exception as e:
        print "send(..) failed executing requests.put(..): " + str(e)

On this page:

• Syntax
• Properties
• cfn-response Module