# Set up Lambda custom integrations in API Gateway
<a name="set-up-lambda-custom-integrations"></a>

 To show how to set up the Lambda custom, or non-proxy,integration, we create an API Gateway API to expose the `GET /greeting?greeter={name}` method to invoke a Lambda function. Use one of the following example Lambda functions for you API.

Use one of the following example Lambda functions:

------
#### [ Node.js ]

```
'use strict';
var days = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];            
var times = ['morning', 'afternoon', 'evening', 'night', 'day'];

export const handler = async(event) => {
  console.log(event);
  // Parse the input for the name, city, time and day property values
  let name = event.name === null || event.name === undefined || event.name === "" ? 'you' : event.name;
  let city = event.city === undefined ? 'World' : event.city;
  let time = times.indexOf(event.time)<0 ? 'day' : event.time;
  let day = days.indexOf(event.day)<0 ? null : event.day;

  // Generate a greeting
  let greeting = 'Good ' + time + ', ' + name + ' of ' + city + '. ';
  if (day) greeting += 'Happy ' + day + '!';
  
  // Log the greeting to CloudWatch
  console.log('Hello: ', greeting);
  
  // Return a greeting to the caller
  return greeting;
};
```

------
#### [ Python ]

```
import json


def lambda_handler(event, context):
    print(event)
    res = {
        "statusCode": 200,
        "headers": {
            "Content-Type": "*/*"
        }
    }

    if event['greeter'] == "":
        res['body'] = "Hello, World"
    elif (event['greeter']):
        res['body'] = "Hello, " + event['greeter'] + "!"
    else:
        raise Exception('Missing the required greeter parameter.')

    return res
```

------

The function responds with a message of `"Hello, {name}!"` if the `greeter` parameter value is a non-empty string. It returns a message of `"Hello, World!"` if the `greeter` value is an empty string. The function returns an error message of `"Missing the required greeter parameter."` if the greeter parameter is not set in the incoming request. We name the function `HelloWorld`.

You can create it in the Lambda console or by using the AWS CLI. In this section, we reference this function using the following ARN:

```
arn:aws:lambda:us-east-1:123456789012:function:HelloWorld
```

With the Lambda function set in the backend, proceed to set up the API.<a name="set-up-lambda-custom-integration-using-cli"></a>

**To set up the Lambda custom integration using the AWS CLI**

1. Use the following [create-rest-api](https://docs.aws.amazon.com/cli/latest/reference/apigateway/create-rest-api.html) command to create an API:

   ```
   aws apigateway create-rest-api --name 'HelloWorld (AWS CLI)'
   ```

   The output will look like the following:

   ```
   {
       "name": "HelloWorld (AWS CLI)", 
       "id": "te6si5ach7",
       "rootResourceId" : "krznpq9xpg",
       "createdDate": 1508461860
   }
   ```

   You use the API `id` ( `te6si5ach7`) and the `rootResourceId` (`krznpq9xpg`) throughout this example.

1. Use the following [create-resource](https://docs.aws.amazon.com/cli/latest/reference/apigateway/create-resource.html) command to create an API Gateway [Resource](https://docs.aws.amazon.com/apigateway/latest/api/API_Resource.html) of `/greeting`:

   ```
   aws apigateway create-resource \
         --rest-api-id te6si5ach7 \
         --parent-id krznpq9xpg \
         --path-part greeting
   ```

   The output will look like the following:

   ```
   {
       "path": "/greeting", 
       "pathPart": "greeting", 
       "id": "2jf6xt", 
       "parentId": "krznpq9xpg"
   }
   ```

   You use the `greeting` resource's `id` value (`2jf6xt`) to create a method on the `/greeting` resource in the next step.

1. Use the following [put-method](https://docs.aws.amazon.com/cli/latest/reference/apigateway/put-method.html) command to create an API method request of `GET /greeting?greeter={name}`:

   ```
   aws apigateway put-method --rest-api-id te6si5ach7 \
          --resource-id 2jf6xt \
          --http-method GET \
          --authorization-type "NONE" \
          --request-parameters method.request.querystring.greeter=false
   ```

   The output will look like the following:

   ```
   {
       "apiKeyRequired": false, 
       "httpMethod": "GET", 
       "authorizationType": "NONE", 
       "requestParameters": {
           "method.request.querystring.greeter": false
       }
   }
   ```

   This API method allows the client to receive a greeting from the Lambda function at the backend. The `greeter` parameter is optional because the backend should handle either an anonymous caller or a self-identified caller.

1. Use the following [put-method-response](https://docs.aws.amazon.com/cli/latest/reference/apigateway/put-method-response.html) command to set up the `200 OK` response to the method request of `GET /greeting?greeter={name}`:

   ```
   aws apigateway put-method-response \
           --rest-api-id te6si5ach7 \ 
           --resource-id 2jf6xt \
           --http-method GET \
           --status-code 200
   ```

   

1. Use the following [put-integration](https://docs.aws.amazon.com/cli/latest/reference/apigateway/put-integration.html) command to set up the integration of the `GET /greeting?greeter={name}` method with a Lambda function, named `HelloWorld`. The function responds to the request with a message of `"Hello, {name}!"`, if the `greeter` parameter is provided, or `"Hello, World!"`, if the query string parameter is not set.

   ```
   aws apigateway put-integration \
           --rest-api-id te6si5ach7 \
           --resource-id 2jf6xt \
           --http-method GET \
           --type AWS \
           --integration-http-method POST \
           --uri arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/arn:aws:lambda:us-east-1:123456789012:function:HelloWorld/invocations \
           --request-templates '{"application/json":"{\"greeter\":\"$input.params('greeter')\"}"}' \
           --credentials arn:aws:iam::123456789012:role/apigAwsProxyRole
   ```

   The mapping template supplied here translates the `greeter` query string parameter to the `greeter` property of the JSON payload. This is necessary because the input to a Lambda function must be expressed in the body.
**Important**  
For Lambda integrations, you must use the HTTP method of `POST` for the integration request, according to the [specification of the Lambda service action for function invocations](https://docs.aws.amazon.com/lambda/latest/api/API_Invoke.html). The `uri` parameter is the ARN of the function-invoking action.  
The output will look like the following:

   ```
   {
       "passthroughBehavior": "WHEN_NO_MATCH", 
       "cacheKeyParameters": [], 
       "uri": "arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/arn:aws:lambda:us-east-1:123456789012:function:HelloWorld/invocations", 
       "httpMethod": "POST", 
       "requestTemplates": {
           "application/json": "{\"greeter\":\"$input.params('greeter')\"}"
       }, 
       "cacheNamespace": "krznpq9xpg", 
       "credentials": "arn:aws:iam::123456789012:role/apigAwsProxyRole", 
       "type": "AWS"
   }
   ```

   The IAM role of `apigAwsProxyRole` must have policies that allow the `apigateway` service to invoke Lambda functions. Instead of supplying an IAM role for `credentials`, you can call the [add-permission](https://docs.aws.amazon.com/cli/latest/reference/lambda/add-permission.html) command to add resource-based permissions. This is how the API Gateway console adds these permissions. 

1. Use the following [put-integration-response](https://docs.aws.amazon.com/cli/latest/reference/apigateway/put-integration-response.html) command to set up the integration response to pass the Lambda function output to the client as the `200 OK` method response:

   ```
    aws apigateway put-integration-response \
           --rest-api-id te6si5ach7 \
           --resource-id 2jf6xt \
           --http-method GET \
           --status-code 200 \
           --selection-pattern ""
   ```

   By setting the selection-pattern to an empty string, the `200 OK` response is the default. 

   The output will look like the following:

   ```
    {
       "selectionPattern": "", 
       "statusCode": "200"
   }
   ```

1. Use the following [create-deployment](https://docs.aws.amazon.com/cli/latest/reference/apigateway/create-deployment.html) command to deploy the API to a `test` stage:

   ```
   aws apigateway create-deployment \
           --rest-api-id te6si5ach7 \
           --stage-name test
   ```

1.  Test the API using the following cURL command in a terminal:

   ```
   curl -X GET 'https://te6si5ach7.execute-api.us-west-2.amazonaws.com/test/greeting?greeter=me' \
     -H 'authorization: AWS4-HMAC-SHA256 Credential={access_key}/20171020/us-west-2/execute-api/aws4_request, SignedHeaders=content-type;host;x-amz-date, Signature=f327...5751'
   ```