### Installation

Source: https://github.com/aws-cloudformation/custom-resource-helper/blob/main/README.md

Instructions on how to install the crhelper library into your Lambda function's root folder.

```shell
cd my-lambda-function/
pip install crhelper -t .

```

--------------------------------

### Example Usage

Source: https://github.com/aws-cloudformation/custom-resource-helper/blob/main/README.md

A comprehensive example demonstrating how to use the crhelper library for creating, updating, and deleting CloudFormation custom resources, including error handling and response data management.

```python
from __future__ import print_function
from crhelper import CfnResource
import logging

logger = logging.getLogger(__name__)
# Initialise the helper, all inputs are optional, this example shows the defaults
helper = CfnResource(json_logging=False, log_level='DEBUG', boto_level='CRITICAL', sleep_on_delete=120, ssl_verify=None)

try:
    ## Init code goes here
    pass
except Exception as e:
    helper.init_failure(e)


@helper.create
def create(event, context):
    logger.info("Got Create")
    # Optionally return an ID that will be used for the resource PhysicalResourceId, 
    # if None is returned an ID will be generated. If a poll_create function is defined 
    # return value is placed into the poll event as event['CrHelperData']['PhysicalResourceId']
    #
    # To add response data update the helper.Data dict
    # If poll is enabled data is placed into poll event as event['CrHelperData']
    helper.Data.update({"test": "testdata"})

    # To return an error to cloudformation you raise an exception:
    if not helper.Data.get("test"):
        raise ValueError("this error will show in the cloudformation events log and console.")
    
    return "MyResourceId"


@helper.update
def update(event, context):
    logger.info("Got Update")
    # If the update resulted in a new resource being created, return an id for the new resource. 
    # CloudFormation will send a delete event with the old id when stack update completes


@helper.delete
def delete(event, context):
    logger.info("Got Delete")
    # Delete never returns anything. Should not fail if the underlying resources are already deleted. 
    # Desired state. 


@helper.poll_create
def poll_create(event, context):
    logger.info("Got create poll")
    # Return a resource id or True to indicate that creation is complete. if True is returned an id 
    # will be generated
    return True


def handler(event, context):
    helper(event, context)

```

--------------------------------

### AWS CDK template example

Source: https://github.com/aws-cloudformation/custom-resource-helper/blob/main/README.md

Example of using AWS CDK to deploy a Custom Resource that utilizes the Custom Resource Helper.

```python
from aws_cdk import (
    ...
    aws_lambda as _lambda,
    CustomResource,
)

crhelperSumResource = _lambda.Function(...)

customResource = CustomResource(
  self, 
  'MyCustomResource'
  serviceToken = crhelperSumResource.function_arn,
  properties = {
    'No1': 1,
    'No2': 2
  },
)


```

--------------------------------

### Polling IAM Policy

Source: https://github.com/aws-cloudformation/custom-resource-helper/blob/main/README.md

The required IAM policy to attach to the Lambda function's role when using the polling feature for longer runtimes.

```json
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "lambda:AddPermission",
        "lambda:RemovePermission",
        "events:PutRule",
        "events:DeleteRule",
        "events:PutTargets",
        "events:RemoveTargets"
      ],
      "Resource": "*"
    }
  ]
}

```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.