Shared Resource

When several Workloads need to use the same real-world Resource, this can be modelled as a Shared Resource.

Workloads using the Shared Resource will then reference the same node in the Resource Graph.

Example: Shared DNS

This example shows a frontend and a backend Workload. Both are exposed via DNS. The frontend is exposed via an external DNS, and it needs to access the backend via it associated DNS name as well. It therefore requires the backend DNS name to be injected as an environment variable.

To achieve this, the backend dns is made a Shared Resource by assigning it an id in Score. Both Score files need to use the same id to reference the same Resource.

Note that the Workloads refer to the Shared Resource using a different resource name (api-dns vs. my-dns). That name is local to the Score file and may be different.

The frontend has an additional dns for its own reachability. All dns resources are used in conjunction with a route.

The respective portions of the Resource Graph will then look like this:

---
title: Resource Graph
---
flowchart LR
    frontend(frontend) --> fe-route(route) --> fe-dns(dns)
    frontend --> fe-dns
    backend(backend) --> be-route(route) --> be-dns(dns)
    frontend ---> be-dns
    backend --> be-dns

Example files:

score-frontend.yaml: Score file for the frontend Workload
score-backend.yaml: Score file for the backend Workload

score-backend.yaml (view on GitHub) :

# Example Score file for a Workload using a Shared Resource to provide its DNS name to another Workload
apiVersion: score.dev/v1b1
metadata:
  name: shared-resource-example-backend

containers:
  backend:
    image: my-be-service:latest

resources:
  # This resource becomes a Shared Resource by assiging it an "id"
  # Other Workloads using the same id will reference the same resource
  my-dns:
    type: dns
    id: backend-dns
  my-route:
    type: route
    params:
      host: ${resources.my-dns.host}
      path: /
      port: 8765

score-frontend.yaml (view on GitHub) :

# Example Score file for a Workload using a Shared Resource to obtain the DNS name of another Workload
apiVersion: score.dev/v1b1
metadata:
  name: shared-resource-example-frontend

containers:
  frontend:
    image: my-fe-service:latest
    variables:
      # Inject the DNS name of the backend service as an environment variable
      API_URL: https://${resources.api-dns.host}

resources:
  # This resource becomes a Shared Resource by assiging it an "id"
  # Other Workloads using the same id will reference the same resource
  api-dns:
    type: dns
    id: backend-dns
  fe-dns:
    type: dns
  fe-route:
    type: route
    host: ${resources.fe-dns.host}
      path: /
      port: 80

Score

Capability

Shared Resource

Example: Shared DNS #

Example: Shared DNS