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createRestAPI.md

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Create REST API

Amazon API Gateway

  • Fully managed service that allows creating a REST API that acts as the front-end for other services.
  • Using API Gateway provides users with a secure HTTP endpoint to invoke your Lambda function and can help manage large volumes of calls to your function by throttling traffic and automatically validating and authorizing API calls.
  • Will allow the web app to invoke the API

Terminonlogy and Concepts

  • REST API: an application programming interface (API or web API) that conforms to the constraints of REST architectural style and allows for interaction with RESTful web services.
  • CORS: Defines a way for client web app that are loaded in one domain to interact with resources in a different domain.

REST - Representational State Transfer

  • Refers to a group of software architecture design constraints that bring about efficient, reliable and scalable distributed systems.
  • Basic idea of REST is that a resource, e.g. a document, is transferred via well-recognized, language-agnostic, and reliably standardized client/server interactions. Services are deemed RESTful when they adhere to these constraints.

CORS - Cross Origin Resource Sharing

  • Is an HTTP-header based mechanism that allows a server to indicate any origins (domain, scheme, or port) other than its own from which a browser should permit loading resources.
  • CORS also relies on a mechanism by which browsers make a "preflight" request to the server hosting the cross-origin resource, in order to check that the server will permit the actual request.
  • In that preflight, the browser sends headers that indicate the HTTP method and headers that will be used in the actual request.
  • An example of a cross-origin request: the front-end JavaScript code served from https://domain-a.com uses XMLHttpRequest to make a request for https://domain-b.com/data.json.
  • For security reasons, browsers restrict cross-origin HTTP requests initiated from scripts.

Implementation

Step 01:

  • In API gateway, choose the REST API and select build
  • Close the prompt and select new api
  • Name the api, in this case serverless
  • Click create

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Step 02:

  • Make sure the the root of the directory you want to add to is selected
  • In the actions menu select create resource
  • Provide a name, in this case dev
  • enable API Gateway CORS
  • Create resource

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Step 03:

  • Make sure the resource directory dev is selected
  • In the actions menu select create method
  • In the dropdown select GET
  • Apply change by clicking check mark
  • Make sure integration type is lambda function
  • Leave use lambda proxy integration unchecked
  • In the lambda function section, input getFeedback
  • Click save

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Step 04:

  • Select GET, then click on test
  • Results should should a feedback item stored in dynamoDB

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Step 05:

  • Create the POST request using postFeedback

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Step 06:

  • To allow the webapp to use the API, CORS must be enabled
  • Make sure the dev directory is selected
  • From actions select enable cors
  • In methods, deselect options
  • Click enable cors and replace existing headers
  • Accept the prompt

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Step 07:

  • The API must be deployed to get the invoke url
  • In actions select deploy api
  • Select and existing stage or create a new one, in this case test
  • Click deploy

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Step 08:

  • Open the invoke url link
  • An error message may appear of "Missing authentication token"
  • This is because it is looking in the wrong address
  • Append /dev at the end of the address and load the page
  • Feedback item from dynamoDB should appear

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Next -> Host web app