feat: add support for baseUrl

[aslafy-z]

Background

I want to host this microservice demo frontend on a subpath (X.X.X.X/online-boutique/). I made my reverse proxy rewrite the url by removing /online-boutique from the paths it sees. However, the frontend html pages uses absolute urls which cannot be solved with the reverse proxy.

Fixes

Change Summary

• Introduce baseUrl from BASE_URL environment variable
• Add baseUrl to default template variables
• Prefix all absolute urls with baseUrl
• Update handlers to use baseUrl
• Update redirects to use baseUrl

Additional Notes

Image is available at docker.io/zadki3l/microservice-demo-frontend:v0.11.0-dev.4

Testing Procedure

• Deploy app with BASE_URL=/online-boutique environment variable.

  Kustomize example

    kind: Kustomization
    namespace: online-boutique
    resources:
    - https://github.com/GoogleCloudPlatform/microservices-demo//kustomize/base?ref=6af73dcf7fe1ca653d95ae7a29e12faf8cf02964
    - namespace.yaml
    - ingress.yaml
    components:
    - https://github.com/GoogleCloudPlatform/microservices-demo//kustomize/components/non-public-frontend?ref=6af73dcf7fe1ca653d95ae7a29e12faf8cf02964
    - https://github.com/GoogleCloudPlatform/microservices-demo//kustomize/components/without-loadgenerator?ref=6af73dcf7fe1ca653d95ae7a29e12faf8cf02964
    images:
     - name: gcr.io/google-samples/microservices-demo/frontend
       newName: docker.io/zadki3l/microservice-demo-frontend
       newTag: v0.11.0
    patches:
    - patch: |-
        - op: add
          path: "/spec/template/spec/containers/0/env/-"
          value:
            name: BASE_URL
            value: "/online-boutique"
      target:
        kind: Deployment
        name: frontend

• Deploy an ingress with /online-boutique prefix.

• Validate that everything shows correctly

Related PRs or Issues

[NimJay]

Thanks for this feature.

It looks like the "You May Also Like" section of each product page is broken in the staging URL:

Do you know if it might be due to a change in the .html templates?

[aslafy-z]

@NimJay I don't think so, the same changes were done on the product listing page without issue: https://github.com/GoogleCloudPlatform/microservices-demo/pull/2609/files#diff-486e203835857587dcd0bd356e4778094d7514a853fcfb8d83b6c0163b471eaeL48-L49.

Edit: My bad, I confirm recommendations are broken. I will look for a solution.

[aslafy-z]

I updated the code to fix Ad and Recommendation templates. I had to pass them the global context. I'm not a fan of that solution, however, it works well.
I pushed an updated image at docker.io/zadki3l/microservice-demo-frontend:v0.11.0-dev.4.