Using Forge on your services

To start using Forge on a new or existing service, the hello-forge example is a good place to start. We'll walk through the steps below, based on the hello-forge example.

1. Create a deployment template in $REPO_HOME/k8s. The deployment template should contain all the necessary information to deploy the service. Forge supports templating the deployment template using the Jinja2 templating engine. When a template is instantiated, all the parameters in the service.yaml file as well as the metadata from the build is included in the output. Here is an example deployment template:

```
---
apiVersion: v1
kind: Service
metadata:
  name: {{service.name}}
spec:
  selector:
    app: {{service.name}}
  ports:
    - protocol: TCP
      port: 80
      targetPort: 5000
  type: LoadBalancer
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata: {name: {{service.name}}}
spec:
  replicas: 1
  selector:
    matchLabels: {app: {{service.name}}}
  strategy:
    rollingUpdate: {maxSurge: 1, maxUnavailable: 0}
    type: RollingUpdate
  revisionHistoryLimit: 1
  template:
    metadata:
      labels: {app: {{service.name}}}
      name: {{service.name}}
    spec:
      containers:
      - image: {{build.images["Dockerfile"]}}
        imagePullPolicy: IfNotPresent
        name: {{service.name}}
        resources:
          limits:
            memory: {{service.memory}}
            cpu: {{service.cpu}}
        terminationMessagePath: /dev/termination-log
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      securityContext: {}
      terminationGracePeriodSeconds: 30
```


The service parameters are supplied to the deployment templates under the `service` variable name. The build metadata is supplied under the `build` variable name, and Docker images are available in the `build.images` map. This map is keyed by path relative to the directory containing the `service.yaml` file.

1. Create a service.yaml file in $REPO_HOME. This file identifies the given directory as a service and contains the metadata supplied to the deployment templates. Here's an example that maps to the above example:

    name: hello
    memory: 0.25G
    cpu: 0.25
   

   Each of these values are interpolated into the deployment template above.

2. Create a Dockerfile in $REPO_HOME. This should specify how the Docker container should be built.

3. That's it! With these 3 files, you can now deploy into Kubernetes with forge deploy.

Still have questions? Ask in our Gitter chatroom or file an issue on GitHub.