# Amazon Managed Streaming for Apache Kafka (Amazon MSK) to AWS Lambda

This pattern deploys a Lambda function that uses an Amazon MSK topic as an event source.

Learn more about this pattern at Serverless Land Patterns: https://serverlessland.com/patterns/msk-lambda

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 msk-lambda
    ```
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

Lambda is a consumer application for your Kafka topic. It processes records from one or more partitions and sends the payload to the target function. Lambda continues to process batches until there are no more messages in the topic.

Lambda internally polls for new messages from the event source and then synchronously invokes the target Lambda function. Lambda reads the messages in batches and provides these to your function as an event payload. The maximum batch size is configurable. (The default is 100 messages.) 

The Lambda function’s event payload contains an array of records. Each array item contains details of the topic and Kafka partition identifier, together with a timestamp and base64 encoded message:

```
{   "eventSource": "aws:kafka",
    "eventSourceArn": "arn:aws:kafka:sa-east-1:123456789012:cluster/vpc-2priv-2pub/751d2973-a626-431c-9d4e-d7975eb44dd7-2",
    "records": {
      "mytopic-0": [
          {
            "topic": "mytopic"
            "partition": "0",
            "offset": 15,
            "timestamp": 1545084650987,
            "timestampType": "CREATE_TIME",
            "value": "SGVsbG8sIHRoaXMgaXMgYSB0ZXN0Lg==",
          }
      ]
    }
}
```

## Testing

1. Publish messages to the Amazon MSK topic.
Follow the steps as outlined in Step 4 to create a client machine and publish messages to the MSK Topic.


2. Retrieve the logs from the Lambda function:
```bash
sam logs -n ENTER_YOUR_CONSUMER_FUNCTION_NAME
```
## Documentation
- [Using Lambda with Amazon MSK](https://docs.aws.amazon.com/lambda/latest/dg/with-msk.html)
- [Using Amazon MSK as an event source for AWS Lambda](https://aws.amazon.com/blogs/compute/using-amazon-msk-as-an-event-source-for-aws-lambda/)
## 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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