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API Gateway Integration Types

Links: 102 AWS DVA Index

Integration Types

In proxy integration types we DONT use mapping templates.

MOCK

  • API Gateway returns a response without sending the request to the backend
  • Just for development and testing

HTTP/AWS (Lambda & AWS Services)

  • Only REST API since HTTP API only supports proxies.
  • For custom integration (HTTP), lambdas and other AWS services (AWS).
  • We must configure both the integration request and integration response
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  • We can setup data mapping using mapping templates to modify the request & response.
    • This means we will be able to change the request made to the backed and change the response received from the backend before sending it to the client.
    • Example: mapping the REST API to an API call on SQS Queue so that SQS queue can understand the API call made by the API Gateway.
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A serverless application is using API Gateway with a non-proxy Lambda Integration. A developer was tasked to expose a GET method on a new /getcourses resource to invoke the Lambda function, which will allow the consumers to fetch a list of online courses in JSON format. The consumers must include a query string parameter named courseType in their request to get the data. What is the MOST efficient solution that the developer should do to accomplish this requirement?

Configure the method request of the resource

Configuring the integration request of the resource is incorrect because although configuring the integration request may also be valid, the client traffic will hit the method request first before it goes to the integration request down to the underlying Lambda function. This is why you should configure the method request first so it won't be necessary to check the required parameters in the Lambda integration.

AWS_PROXY (Lambda Proxy)

  • Incoming request from the client is the input to Lambda
  • The function is responsible for the logic of request/response.
    • Lambda function must return the result in the following JSON format.
  • All the work is done on the backend and API Gateway is there just to proxy the request.
  • NO mapping template, headers, query string parameters, etc are passed as arguments
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HTTP_PROXY

  • NO mapping template
  • The HTTP request is passed to the backend.
    • It can be any backend. It can be an API running on EBS.
  • The HTTP response from the backend is forwarded by API Gateway
  • API Gateway is used just to proxy the request
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Mapping Templates

  • So mapping templates can only be used if we use HTTP/AWS services without proxy.
  • Mapping templates can be used to modify request/responses
  • Type of modification that can be done:
    • Rename/Modify query string parameters
    • Modify body content
    • Add headers
  • Uses Velocity Template Language (VTL): it a scripting language for writing these templates.
  • Filter output results (remove unnecessary data)
In general it is better to use proxy integration types (either lambda or HTTP)

Otherwise you have to learn another scripting language just to modify the request and responses.

Use cases: JSON to XML with SOAP

  • SOAP API are XML based, whereas REST API are JSON based
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  • In this case, API Gateway should:
    • Extract data from the request: either path, payload or header
    • Build SOAP message based on request data (mapping template)
    • Call SOAP service and receive XML response
    • Transform XML response to desired format (like JSON), and respond to the user

Use cases: Renaming Variables

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Last updated: 2023-02-24