Exercise: Implementing resilience in a TypeScript NestJS application

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.

1. 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. Make sure current working directory is /home/user/projects/cloud-sdk-learning-journey.

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      cd ~/projects/cloud-sdk-learning-journey
      git checkout tsnestjs_v2.0_resilience

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2. Build and run the project

   1. Run the application by executing the following commands in the terminal

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      cd cloudsdk_bp_ts
      npm i
      npm run start:dev

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3. Query the Business Partner API of SAP S/4HANA Cloud

   1. Open the requests.http file

   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. Start the Mock Server within 30 seconds. Notice that the resilience configuration allows the application to keep retrying with a time out of 30 seconds. Verify that the list of business partners are returned from the Mock Server since the Mock Server was started within 30 seconds

      

4. Optional: Review code in the following source files

   1. 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

      Code walk-through

      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

5. Optional: Manually create the project

   1. Create or update the following files in the table below

      File name	Type	Contents
      business-partner.service.ts Path: ~/projects/cloudsdk_bp_ts/src/business-partner	Modified	Copy contents from here...