# Deployment types

- There are many different ways to deploy services

- Having an understandig of the differences helps to choose the best one

---

## Simple POD

- An easy thing to deploy is a Pod

- A pod is limited in its ability and therefor often not created manually

- (Cron)jobs, deployments, daemonsets and statefulsets all create (and manage!) pods

  - This allows for better management, scaling etc. (where applicable)

---

## Jobs

- Are one time executions of a Pod

  - Often used to perform a one time action

  - Triggered manually or on a time schedule in which case it is a cron job.

  - Uses a pod template to create pods

---

.small[

```yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: pi
spec:
  template:
    spec:
      containers:
      - name: pi
        image: perl:5.34.0
        command: ["perl",  "-Mbignum=bpi", "-wle", "print bpi(2000)"]
      restartPolicy: Never
  backoffLimit: 4
```

]

---

## Deployments

- The most common deployment types

  - They create Replica Sets

    - Are scalable (manually or automatically)

    - Enablers of rolling updates

    - Used for rollback scenarios

  - Use a pod template to create pods (Using resource sets as intermediates)

  - Share PVC's amongst pods

---

.small[

```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: 80
```

]

---

## Statefulsets

- Less commonly used

  - Scale like Deployments, but slightly different

  - Do NOT share PVC's but have individual ones

  - Differ in update process

- Use a pod template to create pods

---

.small[

```yaml
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  selector:
    matchLabels:
      app: nginx # has to match .spec.template.metadata.labels
  serviceName: "nginx"
  replicas: 3 # by default is 1
  template:
    metadata:
      labels:
        app: nginx # has to match .spec.selector.matchLabels
    spec:
      terminationGracePeriodSeconds: 10
      containers:
      - name: nginx
        image: registry.k8s.io/nginx-slim:0.8
        ports:
        - containerPort: 80
          name: web
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
  - metadata:
      name: www
    spec:
      accessModes: [ "ReadWriteOnce" ]
      storageClassName: "my-storage-class"
      resources:
        requests:
          storage: 1Gi
```

]

---

## Daemonset

- Deploy one pod per node

  - Not more, not less

  - Each new node automatically get's a pod

- Use a pod template to create pods

---

.small[
```yaml
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluentd-elasticsearch
  namespace: kube-system
  labels:
    k8s-app: fluentd-logging
spec:
  selector:
    matchLabels:
      name: fluentd-elasticsearch
  template:
    metadata:
      labels:
        name: fluentd-elasticsearch
    spec:
      containers:
      - name: fluentd-elasticsearch
        image: "quay.io/fluentd_elasticsearch/fluentd:v2.5.2"
        volumeMounts:
        - name: varlog
          mountPath: /var/log
      terminationGracePeriodSeconds: 30
      volumes:
      - name: varlog
        hostPath:
          path: /var/log
```

]
