## cfn_resource.py
This project is a decorator and validation system that takes the drudgery out
of writing custom resources. You still have access to the context and event as
normal, but the decorator handles serializing your response and communicating
results to CloudFormation.
See [cfn-lambda](https://github.com/andrew-templeton/cfn-lambda) from Andrew
Templeton if you're looking to write your custom resources in Node.js.
## Usage
1. Copy `cfn_resource.py` into the directory of your lambda function handler.py
1. Use the `cfn_resource.Resource` event decorators to decorate your handler
like in `example.py`
1. Zip up the contents and upload to Lambda
Once the function is up, copy its ARN and use it as the ServiceToken for your
[custom resource][rsrc]. For more on the requests you may receive, see
[this document][reqdocs]
```json
{
"AWSTemplateFormatVersion": "2010-09-09",
"Resources": {
"FakeThing": {
"Type": "Custom::MyResource",
"Properties": {
"ServiceToken": "arn:aws:lambda:SOME-REGION:ACCOUNT:function:FunctionName",
"OtherThing": "foobar",
"AnotherThing": 2
}
}
}
}
```
For more on how custom resources work, see the [AWS docs][docs]
## Code Sample
For this example, you need to have your handler in Lambda set as
`filename.handler` where filename has the below contents.
```
import cfn_resource
# set `handler` as the entry point for Lambda
handler = cfn_resource.Resource()
@handler.create
def create_thing(event, context):
# do some stuff
return {"PhysicalResourceId": "arn:aws:fake:myID"}
@handler.update
def update_thing(event, context):
# do some stuff
return {"PhysicalResourceId": "arn:aws:fake:myID"}
```
## Running Tests
To run the tests locally, you need Python 2.7 and `pip`. Ideally, you should
use a virtualenv.
```
$ pip install -r test-requirements.txt
$ py.test
```
The tests use `mock` and `py.test` and will give you a terminal coverage
report. Currently the tests cover ~90% of the (very small) codebase.
## License
This code is released under the MIT software license, see LICENSE.txt for
details. No warranty of any kind is included, and the copyright notice must be
included in redistributions.
[rsrc]: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-cfn-customresource.html
[docs]: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-custom-resources.html
[reqdocs]: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/crpg-ref-requests.html
