Lab_3_Building_a_simple_API_Proxy

Lab 3 - Building a simple API Proxy

Overview

Apigee Edge enables you to expose APIs that can be easily consumed by developers who build apps. You expose APIs on Apigee Edge by building API proxies that act as managed 'facades' for backend services.

You expose APIs on Apigee Edge by implementing API proxies. An API proxy is a bundle of XML configuration files and code (such as JavaScript and Java) that implements the facade for your backend HTTP services. API proxies decouple the developer-facing API from your backend services, shielding developers from code changes and enabling you to innovate at the edge without impacting internal applications and development teams. As development teams make backend changes, developers continue to call the same API without any interruption.

API proxies manage request and response messages using a 'pipeline' processing model that defines 'Flows'. To customize the behavior of your API, you attach Policies to request and response Flows.

In an API proxy configuration, there are two types of endpoints:

• ProxyEndpoint: This configuration manages interactions with apps

  that consume your API. You configure the ProxyEndpoint to define the URL of your API. You usually attach Policies to the ProxyEndpoint to enforce security, quota checks, and other types of access control and rate-limiting.

• TargetEndpoint: This configuration manages interactions with

  your backend services on behalf of consumer apps. You configure the TargetEndpoint to forward request messages to the proper backend service. You usually attach Policies to the TargetEndpoint to ensure that response messages are properly formatted for the app that made the initial request.

You can visualize API proxies as shown by the graphic below. A basic request and response exchange between an app (HTTP client) and a backend service is managed in an API proxy by a ProxyEndpoint and TargetEndpoint.

You can build API proxies using the Apigee Edge management UI. You can also implement API proxies on your local machine, and then import them to your organization on Apigee Edge. For an overview of the UI and API, see Using the Apigee Edge development environment.

Objectives

In this lab you will get familiar with the Apigee Edge Management UI by updating the API Proxy that we created in Lab 1 to function as a simple passthrough facade to the GET API for the ‘hotels’ data collection in API BaaS. After creating the facade you will also learn how to deploy and undeploy a proxy. Finally you will also learn how to use the Trace capabilities in the Management UI.

Some API teams build APIs using a Design-First approach where they start with creating a Swagger document – this is what we did in lab 1 and what we will use as the basis for our API Proxy. An alternative approach is **to use a Build-First approach that starts with building an API proxy directly in Apigee Edge. **

Prerequisites

• Labs 1 & 2 are completed

• Postman tool installed and ‘DevJam 2.0’ bundle imported.

Estimated Time: 15 mins

1. Open the API Proxy that we created in lab 1.

   a. Open up a browser tab and log in to http://enterprise.apigee.com

   b. From the Organization drop-down in the top-right corner, select the organization assigned to you.

   c. From the Environment drop-down, select ‘test’

   d. From the main menu, select APIs → API Proxies

a. Click on the link to your API Proxy {yourinitials}_hotels

b. Review the information on the resulting API Proxy page

1. Deploying and Undeploying a Proxy to a given environment from the Management UI is simple too.

   a. Click on the ‘Deploy’ drop-down on the API Proxy page

a. Notice that the proxy we just created is deployed to the ‘test’ environment

b. Click on the ‘test’ environment name. This un-deploys the proxy from the ‘test’ environment

c. Click on the ‘Deploy’ drop-down again and select the ‘test’ environment. This re-deploys the proxy to the ‘test’ environment

1. Tracing the execution of a proxy can also be done easily from the Management UI. This is a very powerful capability of the product since it makes it easy to troubleshoot and monitor API proxies running on Apigee Edge. Trace lets you probe the details of each step through an API proxy flow.

   a. From the ‘{your_initials}_hotels’ API Proxy page, click on the ‘Trace’ tab

a. Once on the ‘Trace’ tab, pick the correct environment from the ‘Deployment to Trace’ drop-down. In your case there should only be one environment to pick - ‘Environment test, Revision 1’

a. Click on the ‘Start Trace Session’ button

b. After the trace session starts, add '/hotels' to the end of the url listed in the box so that it hits the resource "/hotels" imported from the SPEC you imported at proxy creation. Now click on the ‘Send’ button in the ‘Send Requests’ section

a. You will see the a transaction appear in the ‘Transactions’ section and a visual representation of the executed proxy flow in the ‘Transaction Map’ section

b. The ‘Transaction Map’ is interactive - click on the various execution steps within the flow and review the information provided in the ‘Phase Details’ section. You will notice that for each step information such as headers, variables, payload, properties and other relevant information is available. This helps you quickly understand exactly what is happening within the proxy flow.

a. At this point, we will start to use the ‘Postman’ tool as a client to invoke our proxy and continue to use ‘Postman’ throughout the rest of the labs. NOTE: After you import you'll need to update the environment by going to manage environments and then clicking on DevJam2.0. You'll want to set the organization to your current org and then set intials to your own initials.

-   Launch ‘Postman’

-   Select the ‘DevJam 2.0’ environment

• Open the ‘DevJam 2.0’ project

• Select and send the ‘/GET hotels’ request

Note : Please change the URL to point to your API proxy.

• Review the response returned by the proxy. It should be the same response as the one you observed when using the ‘Trace’ tool in the Management UI

a. Switch to the ‘Trace’ tab of the Apigee Edge Management UI and click on the ‘Stop Trace’ button

Summary

That completes this hands-on lesson. Simple and quick, but you learned the fundamentals of how to work with an API Proxy, how to deploy and undeploy it to/from an environment, and how to trace the proxy flow. Throughout the rest of the hands-on labs you will be working with this Management UI to add policies to proxies, testing and tracing these proxies, and learning about the power of the Apigee Edge platform.

Now go to Lab 4.