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Simple service discovery

Explore basic GraphQL service discovery with the Pet Store sample application.

Start by deploying the Pet Store sample application, which you will expose behind a GraphQL server embedded in Envoy.

kubectl apply -f - <<EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: petstore
  name: petstore
  namespace: default
spec:
  selector:
    matchLabels:
      app: petstore
  replicas: 1
  template:
    metadata:
      labels:
        app: petstore
    spec:
      containers:
      - image: openapitools/openapi-petstore
        name: petstore
        env:
          - name: DISABLE_OAUTH
            value: "1"
          - name: DISABLE_API_KEY
            value: "1"
        ports:
        - containerPort: 8080
          name: http
---
apiVersion: v1
kind: Service
metadata:
  name: petstore
  namespace: default
  labels:
    service: petstore
spec:
  ports:
  - port: 8080
    protocol: TCP
  selector:
    app: petstore
EOF

Optional: Check the unfiltered JSON output for the Pet Store service.

Create a route for the service.

glooctl add route --name default --namespace gloo-system --path-prefix / --dest-name default-petstore-8080 --dest-namespace gloo-system

Send a /GET request to /v3/pet/10 of this service.

curl "$(glooctl proxy url)/v3/pet/10" -H 'Accept: application/json'

Example unfiltered JSON output:

{"id":10,"category":{"id":3,"name":"Rabbits"},"name":"Rabbit 1","photoUrls":["url1","url2"],"tags":[{"id":1,"name":"tag3"},{"id":2,"name":"tag4"}],"status":"available"}

Verify that OpenAPI specification discovery is enabled, and that Gloo Edge created a corresponding GraphQL custom resource.
```
kubectl get graphqlapis -n gloo-system
```
Example output:
```
NAME                    AGE
default-petstore-8080   2m58s
```

Optional: Check out the generated GraphQL schema.

kubectl get graphqlapis default-petstore-8080 -o yaml -n gloo-system

Create a virtual service that defines a Route with a graphqlApiRef as the destination. In this example, all traffic to /graphql is handled by the GraphQL server in the Envoy proxy.

cat << EOF | kubectl apply -f -
apiVersion: gateway.solo.io/v1
kind: VirtualService
metadata:
  name: 'default'
  namespace: 'gloo-system'
spec:
  virtualHost:
    domains:
    - '*'
    routes:
    - graphqlApiRef:
        name: default-petstore-8080
        namespace: gloo-system
      matchers:
      - prefix: /graphql
EOF

Send a request to the endpoint to verify that the request is successfully resolved by Envoy. For example, if you want only the name of the pet given the pet’s ID:
```
curl "$(glooctl proxy url)/graphql" -H 'Content-Type: application/json' -d '{"query": "query {getPetById(petId: 10) {name}}"}' 
```
Example successful response:
```
{"data":{"getPetById":{"name":"Rabbit 1"}}}
```

This JSON output is filtered only for the desired data, as compared to the unfiltered response that the Pet Store app returned to the GraphQL server:

{"id":10,"category":{"id":3,"name":"Rabbits"},"name":"Rabbit 1","photoUrls":["url1","url2"],"tags":[{"id":1,"name":"tag3"},{"id":2,"name":"tag4"}],"status":"available"}

Data filtering is one advantage of using GraphQL instead of querying the upstream directly. Because the GraphQL query is issued for only the name of the pets, GraphQL is able to filter out any data in the response that is irrelevant to the query, and return only the data that is specifically requested.

Up next: Explore local GraphQL resolution with the Bookinfo sample application.