View Source FLAMEK8sBackend (flame_k8s_backend v0.5.6)

Kubernetes Backend implementation.

Usage

Configure the flame backend in our configuration or application setup:

# application.ex
children = [
  {FLAME.Pool,
    name: MyApp.SamplePool,
    backend: FLAMEK8sBackend,
    min: 0,
    max: 10,
    max_concurrency: 5,
    idle_shutdown_after: 30_000}
]

Options

The following backend options are supported:

• :app_container_name - If your application pod runs multiple containers (initContainers excluded), use this option to pass the name of the container running this application. If not given, the first container in the list of containers is used to lookup the contaienr image, env vars and resources to be used for the runner pods.

• :omit_owner_reference - If true, no ownerReferences are configured on the runner pods. Defaults to false

• :runner_pod_tpl - If given, controls how the runner pod manifest is generated. Can be a function of type FLAMEK8sBackend.RunnerPodTemplate.callback/0 or a struct of type FLAMEK8sBackend.RunnerPodTemplate.t/0. A callback receives the manifest of the parent pod as a map and should return the runner pod's manifest as a map(). If a struct is given, the runner pod's manifest will be generated with values from the struct if given or from the parent pod if omitted. If this option is omitted, the parent pod's env and resources are used for the runner pod. See FLAMEK8sBackend.RunnerPodTemplate for more infos.

• :log - The log level to use for verbose logging. Defaults to false.

Prerequisites

In order for this to work, your application needs to meet some requirements.

Env Variables

In order for the backend to be able to get informations from your pod and use them for the runner pods (e.g. env variables), you have to define POD_NAME and POD_NAMESPACE environment variables on your pod.

apiVersion: apps/v1
kind: Deployment
spec:
selector:
  matchLabels:
    app: myapp
template:
  spec:
    containers:
      - env:
        - name: POD_NAME
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: metadata.name
        - name: POD_NAMESPACE
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: metadata.namespace

RBAC

Your application needs run as a service account with permissions to manage pods. This is a simple

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: myapp
  namespace: app-namespace
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  namespace: app-namespace
  name: pod-mgr
rules:
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["create", "get", "list", "delete", "patch"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: myapp-pod-mgr
  namespace: app-namespace
subjects:
- kind: ServiceAccount
  name: myapp
  namespace: app-namespace
roleRef:
  kind: Role
  name: pod-mgr
  apiGroup: rbac.authorization.k8s.io
---
apiVersion: apps/v1
kind: Deployment
spec:
  template:
    spec:
      serviceAccountName: my-app

Clustering

Your application needs to be able to form a cluster with your runners. Define POD_IP, RELEASE_DISTRIBUTION and RELEASE_NODE environment variables on your pods as follows:

apiVersion: apps/v1
kind: Deployment
spec:
template:
  spec:
    containers:
      - env:
        - name: POD_IP
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: status.podIP
        - name: RELEASE_DISTRIBUTION
          value: name
        - name: RELEASE_NODE
          value: my_app@$(POD_IP)