# Amazon API Gateway to AWS Lambda with observability features

This pattern shows how to add observability to your serverless appliocation stack - alarms, logs, custom metrics, dashboards

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

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 apigw-lambda-observability
    ```
1. From the command line, use AWS SAM to deploy the AWS resources for the pattern as specified in the template.yml file:
    ```
    npm install
    sam build
    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, API endpoint and Amazon CloudWatch dashboard URL, Amazon SNS topic name.

## How it works

This pattern deploys Amazon API Gateway HTTP API with a single route that is integrated with and AWS Lambda function written in Node.js. The function returns request payload as a response.

Pattern implements logging using CloudWatch Logs, Lambda function emits custom metrics using [Embedded Metrics Format](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch_Embedded_Metric_Format.html), configures CloudWatch alerts, and creates a CloudWatch dashboard. X-Ray distributed tracing is enabled as well. API Gateway access logging is enabled with a 30 day retention period. SAM template overrides the default Lambda log stream to set the retention period to 7 days.

Implementation also includes Amazon SNS topic used by API Gateway and Lambda alerts. To receive alerts you will need to create a subscription for the SNS topic. See [documentation](https://docs.aws.amazon.com/sns/latest/dg/sns-create-subscribe-endpoint-to-topic.html) for instructions.

For extended examples of this pattern, including Python and AWS CDK versions, see [Serverless Samples repository](https://github.com/aws-samples/serverless-samples/tree/main/serverless-rest-api) 


## Testing

Once the CloudFormation stack is deployed get its outputs either in AWS Management Console or by using AWS CLI:
```bash
    aws cloudformation describe-stacks --stack-name STACK_NAME --query "Stacks[0].Outputs"
```

To test this pattern deployment please navigate to the API endpoint URL available in the stack outputs. You should see API Gateway request payload returned by the Lambda function. Repeat this request few times. 

After a few API requests, open CloudWatch dashboard created by this application using URL present in the stack outputs. It should show select API Gateway and Lambda metrics, application custom metrics, alarm statuses and the last 100 AWS Lambda errors (if any) over dashboard time range. You may need to wait couple of minutes before data becomes available.


## 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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