Deploy a Go PostgreSQL API Endpoint in SAP BTP, Kyma Runtime

1. In your browser, go to kyma-runtime-samples. This repository contains a collection of Kyma sample applications which will be used during the tutorial.

2. Use the Code button to choose one of the options to download the code locally, or simply run the following command within your CLI at your desired folder location:

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   git clone https://github.com/SAP-samples/kyma-runtime-samples
   

1. Open the api-postgresql-go directory in your desired editor.

2. Explore the content of the sample.

   Within the cmd/api directory, you can find main.go, which is the main entry point of the Go application.

   The docker directory contains the Dockerfile used to generate the Docker image. The image is built in two stages to create an image with a small file size.

   In the first stage, a Go image is used. It copies the related content of the project into the image and builds the application. The built application is then copied into the Docker scratch image and exposed on port 8000. The scratch image is an empty image containing no other tools within it, so obtaining a shell/bash session is not possible. If desired, the following lines could be commented out to build an image with more included tools, but this results in a larger image.

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   FROM scratch
   WORKDIR /app
   COPY --from=builder /app/api-postgres-go /app/
   

   The internal directory contains the rest of the Go application, broken down into three packages: api, config, and db. You can explore their contents to understand the structure and functionality.

   Within the k8s directory you can find the Kubernetes/Kyma resources you will apply to your SAP BTP, Kyma runtime.

   Within the root, you can find go.mod and go.sum files that are used to manage the dependencies the application uses.

Run the following commands from the api-postgresql-go directory in your CLI.

Make sure to replace the value of <your-docker-id> with your Docker account ID.

If you’re using any device with a non-x86 processor (e.g. MacBook M1/M2) you need to instruct Docker to use x86 images by setting the DOCKER_DEFAULT_PLATFORM environment variable using the command export DOCKER_DEFAULT_PLATFORM=linux/amd64. Check Environment variables for more information.

1. To build the Docker image, run this command:

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   docker build -t <your-docker-id>/api-postgresql-go -f docker/Dockerfile .
   

2. To push the Docker image to your Docker repository, run this command:

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   docker push <your-docker-id>/api-postgresql-go
   

You can find the resource definitions in the k8s folder. If you performed any changes in the configuration, these files may also need to be updated. The folder contains the following files that are relevant to this tutorial:

• apirule.yaml: defines the API endpoint which exposes the application to the Internet. This endpoint does not define any authentication access strategy and should be disabled when not in use.
• authorizationpolicy.yaml: allows internal traffic to the service api-postgresql-go in the dev namespace.
• configmap.yaml: defines the name of the database.
• deployment.yaml: defines the deployment definition for the Go API, as well as a service used for communication. This definition references the PostgreSQL Service Binding Secret (postgres-binding) for connection details and configmap.yaml for the database name.

1. Within the deployment.yaml, adjust the value of spec.template.spec.containers.image, commented with #change it to your image, to use your Docker image. Also ensure the Secret name matches your PostgreSQL Service Binding (postgres-binding). Apply the ConfigMap and Deployment:

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   kubectl -n dev apply -f ./k8s/configmap.yaml
   kubectl -n dev apply -f ./k8s/deployment.yaml
   

2. Verify the status of the Pod by running:

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   kubectl -n dev get po
   

   The Pod should now be running.

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   NAME                               READY   STATUS    RESTARTS   AGE
   api-postgresql-go-c694bc847-tkthc   2/2     Running   0          23m
   

3. Run the following command to get the domain name of your Kyma cluster:

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   kubectl get gateways.networking.istio.io -n kyma-system kyma-gateway \
       -o jsonpath='{.spec.servers[0].hosts[0]}'
   

   The result looks like this:

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   *.<xyz123>.kyma.ondemand.com
   

4. Copy the result without the leading *..

5. In apirule.yaml, modify allowOrigins.regex, to match your domain, and add the exact: http://localhost:8080 key-value pair. For example:

   Note: The command output uses *. as a glob wildcard prefix, but in the regex field you replace it with .* — the equivalent regex pattern that matches any character sequence. For example, *.<xyz123>.kyma.ondemand.com becomes the regex .*xyz123.kyma.ondemand.com.

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     ... 
       allowOrigins:
         - regex: ".*xyz123.kyma.ondemand.com"
         - exact: http://localhost:8080
     ...
   

   exact: http://localhost:8080 is only required if you want to locally test the frontend of your application as part of the Deploy the SAPUI5 Frontend in SAP BTP, Kyma Runtime tutorial.

6. Apply the APIRule:

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   kubectl -n dev apply -f ./k8s/apirule.yaml
   

7. Apply the AuthorizationPolicy:

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   kubectl -n dev apply -f ./k8s/authorizationpolicy.yaml
   

To access the API, use the APIRule you created in the previous step.

1. Open Kyma dashboard.

2. From the menu, choose Namespaces.

3. Choose the dev namespace.

4. From the menu, choose Discovery and Network > API Rules.

5. Choose the Host entry for the api-postgresql-go APIRule to open the application in the browser, which will produce a 404 error. Append /orders to the end of the URL and refresh the page to successfully access the API. The URL should be similar to:

   https://api-postgresql-go.<cluster>.kyma.ondemand.com/orders

   You can use a tool such as curl to test the various HTTP methods of the API.