Using SNS Service Integration from API Gateway

Introduction

This is a tutorial on setting up AWS API GW to talk to SNS. The code below is in Powershell. You should verify your setup from the console as you follow along.

References

• API Proxy Integration
• API to SNS

Create SNS Topic

Nothing fancy. Just regular topic. Keep the ARN handy

Create IAM Role

Create a new IAM Role with following properties. Keep this ARN handy.

• Permission Policy

  {
    "Version": "2012-10-17",
    "Statement": [
      {
          "Effect": "Allow",
          "Action": [
              "sns:Publish"
          ],
          "Resource": "arn:aws:sns:us-east-1:999999999999:delete_me_hyon"
      }
    ]
  }  
  

• Trust Policy

  {
    "Version": "2012-10-17",
    "Statement": [
      {
          "Effect": "Allow",
          "Principal": {
              "Service": "apigateway.amazonaws.com"
          },
          "Action": "sts:AssumeRole"
      }
    ]
  }  
  

  API GW

  Create REST API

  You can also verify via console here:

Create a Resource

Create a resource under root called my_ingest

$INGEST_RESOURCE_ID = aws apigateway create-resource `   
  --rest-api-id $API_ID `
  --parent-id $ROOT_RESOURCE_ID `
  --path-part my_ingest `
  --output text `
  --query 'id' `
  --region $REGION

Create a method

Create a method

aws apigateway put-method `
  --rest-api-id $API_ID `
  --resource-id $INGEST_RESOURCE_ID `
  --http-method POST `
  --authorization-type NONE `
  --region $REGION

Put integration

$requesttemplates = '{\"application/json\":' +  '\"Action=Publish&TopicArn=$util.urlEncode(''' + $SNS_TOPIC_ARN + ''')&Message=$util.urlEncode($input.body)\"}'
aws apigateway put-integration `
  --rest-api-id $API_ID `
  --resource-id $INGEST_RESOURCE_ID `
  --http-method POST `
  --type AWS `
  --integration-http-method POST `
  --uri "arn:aws:apigateway:${REGION}:sns:path//" `
  --credentials $ROLE_ARN `
  --request-parameters '{\"integration.request.header.Content-Type\" : \"''application/x-www-form-urlencoded''\"}' `
  --request-templates $requesttemplates `
  --passthrough-behavior NEVER

Expected Output:

{
    "type": "AWS",
    "httpMethod": "POST",
    "uri": "arn:aws:apigateway:us-east-1:sns:path//",
    "credentials": "arn:aws:iam::999999999999:role/delete_me_hyon",
    "requestParameters": {
        "integration.request.header.Content-Type": "'application/x-www-form-urlencoded'"
    },
    "requestTemplates": {
        "application/json": "Action=Publish&TopicArn=$util.urlEncode('arn:aws:sns:us-east-1:999999999999:delete_me_hyon')&Message=$util.urlEncode($input.body)"
    },
    "passthroughBehavior": "NEVER",
    "timeoutInMillis": 29000,
    "cacheNamespace": "cvevrl",
    "cacheKeyParameters": []
}

Put integration Response

aws apigateway put-integration-response `
  --rest-api-id $API_ID `
  --resource-id $INGEST_RESOURCE_ID `
  --http-method POST `
  --status-code 200 `
  --response-templates '{\"application/json\": \"{''body'': ''Message received.''}\"}' 

Expected Output:

{
    "statusCode": "200",
    "selectionPattern": "\"\"",
    "responseTemplates": {
        "application/json": "{'body': 'Message received.'}"
    }
}

Put Method Response

aws apigateway put-method-response `
  --rest-api-id $API_ID `
  --resource-id $INGEST_RESOURCE_ID `
  --http-method POST `
  --status-code 200 `
  --response-models '{\"application/json\": \"Empty\" }'

Expected Output:

{
    "statusCode": "200",
    "responseModels": {
        "application/json": "Empty"
    }
}

Deploy it

aws apigateway create-deployment --rest-api-id $API_ID --stage-name prod

Expected Output:

{
    "id": "55n8z8",
    "createdDate": "2022-02-06T15:29:21-06:00"
}

Test it

• Click here to test
• Expected Output