Exposing services on the application network using YAML¶

Use YAML to create connectors and listeners for services on the application network.

After creating an application network by linking sites, you can expose services from one site using connectors and consume those services on other sites using listeners. A routing key is a string that matches one or more connectors with one or more listeners. For example, if you create a connector with the routing key backend, you need to create a listener with the routing key backend to consume that service.

This section assumes you have created and linked at least two sites.

Creating a connector using YAML¶

A connector binds a local workload to listeners in remote sites. Listeners and connectors are matched using routing keys.

For more information about connectors see Connector concept. For configuration details, see Connector resource.

Procedure

Create a workload that you want to expose on the network, for example:

kubectl create deployment backend --image quay.io/skupper/hello-world-backend --replicas 3

Create a connector resource YAML file:
```
apiVersion: skupper.io/v2alpha1
kind: Connector
metadata:
  name: backend
  namespace: east
spec:
  routingKey: backend
  selector: app=backend
  port: 8080
```
This creates a connector in the east site and exposes the backend deployment on the network on port 8080. You can create a listener on a different site using the matching routing key backend to address this service.

To create the connector resource:

skupper system apply -f <filename>

where <filename> is the name of a YAML file that is saved on your local filesystem.

Check the connector status:
```
skupper connector status
```

For example:

NAME    STATUS  ROUTING-KEY     SELECTOR        HOST    PORT    HAS MATCHING LISTENER    MESSAGE
backend Pending backend         app=backend             8080    false   No matching listeners

📌 NOTE By default, the routing key name is set to the name of the connector. If you want to use a custom routing key, set spec.routingKey to your custom value.

Creating a listener using YAML¶

A listener binds a local connection endpoint to connectors in remote sites. Listeners and connectors are matched using routing keys.

For more information about listeners, see Listener concept. For configuration details, see Listener resource.

Procedure

Identify a connector that you want to use. Note the routing key of that connector.
Create a listener resource YAML file:
```
apiVersion: skupper.io/v2alpha1
kind: Listener
metadata:
  name: backend
  namespace: west
spec:
  routingKey: backend
  host: east-backend
  port: 8080
```
This creates a listener on the local system site and matches it with connectors that use the routing key backend. The listener accepts connections on port 8080 using the configured host value.

To create the listener resource:

skupper system apply -f <filename>

where <filename> is the name of a YAML file that is saved on your local filesystem.

Check the listener status:
```
skupper listener status
```

For example:

NAME      STATUS  ROUTING-KEY  HOST     PORT  MATCHING-CONNECTOR  MESSAGE
backend   Ready   backend      0.0.0.0  8080  true                OK

📌 NOTE There must be a MATCHING-CONNECTOR for the service to operate.