# AWS Lambda to AWS Systems Manager Parameter Store

This pattern is a Java port of the original [pattern](https://serverlessland.com/patterns/lambda-ssm).

This pattern creates an AWS Lambda function and an AWS Systems Manager Parameter Store parameter.

Learn more about this pattern at Serverless Land Patterns: << Add the live URL here >>

Important: this application uses various AWS services and there are costs associated with these services after the Free Tier usage - please see the [AWS Pricing page](https://aws.amazon.com/pricing/) for details. You are responsible for any AWS costs incurred. No warranty is implied in this example.

## Requirements

* [Create an AWS account](https://portal.aws.amazon.com/gp/aws/developer/registration/index.html) if you do not already have one and log in. The IAM user that you use must have sufficient permissions to make necessary AWS service calls and manage AWS resources.
* [AWS CLI](https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2.html) installed and configured
* [Git Installed](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git)
* [AWS Serverless Application Model](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-install.html) (AWS SAM) installed

## Deployment Instructions

1. Create a new directory, navigate to that directory in a terminal and clone the GitHub repository:
    ``` 
    git clone https://github.com/aws-samples/serverless-patterns
    ```
1. Change directory to the pattern directory:
    ```
    cd lambda-ssm-parameter-java
    ```
1. From the command line, use AWS SAM to deploy the AWS resources for the pattern as specified in the template.yml file:
    ```
    sam deploy --guided
    ```
1. During the prompts:
    * Enter a stack name
    * Enter the desired AWS Region
    * Allow SAM CLI to create IAM roles with the required permissions.

    Once you have run `sam deploy --guided` mode once and saved arguments to a configuration file (samconfig.toml), you can use `sam deploy` in future to use these defaults.

1. Note the outputs from the SAM deployment process. These contain the resource names and/or ARNs which are used for testing.

## How it works

This pattern creates an AWS Lambda function and an AWS Systems Manager Parameter Store parameter. The parameter is added as a function environment variable named "SSMParameterName". The function execution role only allows Get and Put actions on the parameter. The function supports a JSON event in the following format:

```
{
  "method": "{GET || PUT}",
  "body": "{NewParameterValue}"
}
```

The method can be either GET (retrieve current parameter value) or PUT (update parameter with new value). The body of the event is used to define the new value of the parameter.

## Testing

Once the application is deployed, navigate to the Lambda function and configure GET and PUT test events. Invoke the function using each test event. Review the Amazon CloudWatch Logs for details on the function invocation. Navigate to the AWS Systems Manager Paramater Store to observe changes to the parameter value after a PUT event.

Example GET test event:
```
{
  "method": "GET",
  "body": ""
}
```

Response:
```
"GetParameterResponse(Parameter=Parameter(Name=ExampleParameterName, Type=String, Value=*** Sensitive Data Redacted ***, Version=2, LastModifiedDate=2022-04-09T03:28:12.522Z, ARN=arn:aws:ssm:ap-southeast-2:948775074380:parameter/ExampleParameterName, DataType=text))"
```

Example PUT test event:
```
{
  "method": "PUT",
  "body": "{\"key1\":\"value1\", \"key2\":\"value2\"}"
}
```

Response: 
```
"PutParameterResponse(Version=3, Tier=Standard)"
```

## Cleanup
 
1. Delete the stack
    ```bash
    aws cloudformation delete-stack --stack-name STACK_NAME
    ```
1. Confirm the stack has been deleted
    ```bash
    aws cloudformation list-stacks --query "StackSummaries[?contains(StackName,'STACK_NAME')].StackStatus"
    ```
----
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