Exercise: Implementing Resilience in a TypeScript NestJS Applicat

In this exercise, you will learn how to implement resilience in SAP Cloud SDK application. We will use the Mock Server instead of the actual SAP S/4HANA Cloud.

Prerequisites

For the complete execution of current exercise, you must execute the following activities first, using SAP Business Application Studio:

Execute the following exercises:
- Creating your free trial account in SAP BTP
- Setting up the mock server, so that you have the Mock server program available in the cloud-s4-sdk-book folder.
Run the following commands in a terminal, in case you didn't do it already in previous exercises, to clone the Git repository for the course:
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```
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cd ~/projects
git clone https://github.com/SAP-samples/cloud-sdk-learning-journey.git
```
Choose File → Open Folder and open the /home/user/projects/cloud-sdk-learning-journey/ folder.

Steps

Checkout the branch tsnestjs_v2.0_resilience in SAP Business Application Studio
1. Open SAP Business Application Studio.
2. Run the following commands in the terminal.
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```
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cd ~/projects/cloud-sdk-learning-journey
git checkout -f tsnestjs_v2.0_resilience
```
Build and run the project
1. Run the application by executing the following commands in the terminal
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```
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cd cloudsdk_bp_ts
npm i
npm run start:dev
```
Make sure that the Mock Server is up and running as described in the related previous exercise.
1. In case the Mock server is installed but not started, you need to open a new terminal window and run the following commands:
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```
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cd ~/projects/cloud-s4-sdk-book
npm run start
```
Query the Business Partner API of SAP S/4HANA Cloud
1. Open the requests.http file in the cloudsdk_bp_ts folder
2. Click on Send Request in the requests.http file to submit the GET request for business partners
3. Verify that the list of business partners are returned from the Mock Server. Note: If the Mock Server is not running, make sure to run the Mock Server on port 8081 by following the prerequisites at the top
4. Stop the Mock Server by pressing Ctrl + C in the Mock Server project terminal
5. Click on Send Request in the requests.http file to submit the GET request for business partners
6. The request does not fail immediately. But will wait for the timeout period of 30 seconds. Start the Mock Server before 30 seconds
7. Notice that the request instead of failing is able to recover and get the business partners now that the Mock Server was started within the timeout period of 30 seconds

Optional: code walk-through.

Review code in the following source files:

File name	Comments on code changes
business-partner.service.ts	Code logic is as follows... Import resilience from the @sap-cloud-sdk/resilience module Use the middleware function to build a resilience middleware. In our example, we will use the following values timeout: 30 seconds circuitBreaker: true retry: true
package.json	New SAP Cloud SDK modules have been installed for the project
requests.http	Provides various HTTP requests that can be submitted to query the Business Partner API
commands.txt	Provides various commands that can be run on the terminal

Note

Check out the SAP Cloud SDK documentation on Executing an OData GET request using SAP Cloud SDK for JavaScript. https://sap.github.io/cloud-sdk/docs/js/tutorials/getting-started/execute-an-odata-request

Exercise: Implementing Resilience in a TypeScript NestJS Application

Implementing resilience in a TypeScript NestJS application

Prerequisites

Steps