FLAMEK8sBackend

https://hexdocs.pm/flame_k8s_backend/
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FLAMEK8sBackend is a FLAME Backend for Kubernetes that manages pods as runners in the cluster the...
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### Configure FLAMEK8sBackend in Application Setup

Source: https://hexdocs.pm/flame_k8s_backend/FLAMEK8sBackend.html

Configure the FLAME backend in your application's setup. This example shows how to integrate FLAMEK8sBackend with FLAME.Pool.

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

--------------------------------

### Configure FLAME Pool with K8s Backend

Source: https://hexdocs.pm/flame_k8s_backend/index.html

Configure the FLAME pool in your application's setup to use the FLAMEK8sBackend. This example shows basic pool configuration with logging enabled.

```elixir
children = [
  {FLAME.Pool,
    name: MyApp.SamplePool,
    backend: FLAMEK8sBackend,
    min: 0,
    max: 10,
    max_concurrency: 5,
    idle_shutdown_after: 30_000,
    log: :debug}
]
```

--------------------------------

### Add flame_k8s_backend to Dependencies

Source: https://hexdocs.pm/flame_k8s_backend/index.html

Add the flame_k8s_backend dependency to your project's `deps.ex` file to install it.

```elixir
def deps do
  [
    {:flame_k8s_backend, ">= 0.6.0"}
  ]
end
```

--------------------------------

### Configure FLAME Pool with FLAMEK8sBackend

Source: https://hexdocs.pm/flame_k8s_backend/readme.html

Configure the FLAME Pool in your application's `application.ex` file to use FLAMEK8sBackend. Ensure you set appropriate values for `min`, `max`, `max_concurrency`, `idle_shutdown_after`, and `log`.

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

--------------------------------

### Define POD_NAME and POD_NAMESPACE Environment Variables

Source: https://hexdocs.pm/flame_k8s_backend/FLAMEK8sBackend.html

Configure your deployment to set POD_NAME and POD_NAMESPACE environment variables. These are crucial for the backend to gather information from your pod.

```yaml
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
```

--------------------------------

### Configure Clustering Environment Variables

Source: https://hexdocs.pm/flame_k8s_backend/readme.html

Set `POD_IP`, `RELEASE_DISTRIBUTION`, and `RELEASE_NODE` environment variables for your pods to enable clustering with runners. The `RELEASE_NODE` should dynamically include the pod's IP address.

```yaml
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)
```

--------------------------------

### Configure Runner Pod Manifest with Map

Source: https://hexdocs.pm/flame_k8s_backend/changelog.html

Use this when migrating from :runner_pod_tpl to the new :manifest option. Pass a map to define the runner pod's manifest, including environment variables and resource limits.

```elixir
manifest = %{
  "spec" => %{
    "containers" => [
      %{
        "env" => [
          %{"name" => "FOO", "value" => "bar"}
        ],
        "resources" => %{
          "requests" => %{"memory" => "256Mi", "cpu" => "100m"},
          "limits" => %{"memory" => "256Mi", "cpu" => "400m"}
        }
      }
    ]
  }
}

{FLAME.Pool,
  name: MyApp.SamplePool,
  backend: {FLAMEK8sBackend, manifest: manifest}}
```

--------------------------------

### Dynamically Build Runner Pod Manifest with Function

Source: https://hexdocs.pm/flame_k8s_backend/FLAMEK8sBackend.html

Construct the runner pod manifest dynamically by passing a function to the backend. This allows copying configuration from the parent pod.

```elixir
manifest_fun = fn parent_pod_manifest, app_container ->
  %{"metadata" => %{ # ... }, "spec" => %{"containers" => [ %{ # Copy all env vars and resources from the parent container definition. "env" => app_container["env"] || [], "envFrom" => app_container["envFrom"] || [], "resources" => app_container["resources"] || %{} } ]}}
end

FLAME.Pool,
 name: MyApp.SamplePool,
 backend: {FLAMEK8sBackend, manifest: manifest_fun}}
```

--------------------------------

### Configure RBAC for Pod Management

Source: https://hexdocs.pm/flame_k8s_backend/FLAMEK8sBackend.html

Set up a ServiceAccount, Role, and RoleBinding to grant your application the necessary permissions to manage pods. Ensure the service account name matches the one specified in the deployment.

```yaml
---
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
```

--------------------------------

### Add FLAMEK8sBackend to Dependencies

Source: https://hexdocs.pm/flame_k8s_backend/readme.html

Add the flame_k8s_backend dependency to your project's `deps.ex` file.

```elixir
def deps do
  [
    {:flame_k8s_backend, "~> 0.6.0"}
  ]
end
```

--------------------------------

### Define Clustering Environment Variables

Source: https://hexdocs.pm/flame_k8s_backend/FLAMEK8sBackend.html

Configure POD_IP, RELEASE_DISTRIBUTION, and RELEASE_NODE environment variables for your pods to enable clustering with runners. The RELEASE_NODE is dynamically set using the pod's IP.

```yaml
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)
```

--------------------------------

### Configure Runner Pod Manifest with Function

Source: https://hexdocs.pm/flame_k8s_backend/changelog.html

Use this to maintain the behavior of copying envs and resources from the parent pod when using the :manifest option. The function receives the parent pod manifest and app container definition.

```elixir
manifest_fun = fn parent_pod_manifest, app_container ->
    %{
      "spec" => %{
        "containers" => [
          %{
            # Copy env vars and resources from the parent container definition.
            # For fields that you don't want to copy, you can specify the desired
            # values here.
            "env" => app_container["env"] || [],
            "envFrom" => app_container["envFrom"] || [],
            "resources" => app_container["resources"] || %{}
          }
        ]
      }
    }
  end

FLAME.Pool,
  name: MyApp.SamplePool,
  backend: {FLAMEK8sBackend, manifest: manifest_fun}}
```

--------------------------------

### Configure Runner Pod Manifest with Elixir Map

Source: https://hexdocs.pm/flame_k8s_backend/FLAMEK8sBackend.html

Set environment variables and resources for the runner pod using an Elixir map. This is useful for straightforward manifest configurations.

```elixir
manifest = %{
  "spec" => %{
    "containers" => [
      %{
        "env" => [
          %{"name" => "FOO", "value" => "bar"}
        ],
        "resources" => %{
          "requests" => %{"memory" => "256Mi", "cpu" => "100m"},
          "limits" => %{"memory" => "256Mi", "cpu" => "400m"}
        }
      }
    ]
  }
}

{FLAME.Pool,
 name: MyApp.SamplePool,
 backend: {FLAMEK8sBackend, manifest: manifest}}
```

--------------------------------

### Configure Runner Pod Manifest with YAML Sigil

Source: https://hexdocs.pm/flame_k8s_backend/FLAMEK8sBackend.html

Define complex runner pod manifests using YAML within Elixir code via the `~y` sigil. Requires the `:yaml_elixir` package.

```elixir
manifest = ~y"""
metadata:
  spec:
    containers:
      - resources:
          requests:
            memory: 256Mi
            cpu: 100m
          limits:
            memory: 256Mi
            cpu: 400m
      - env:
          - name: FOO
            value: bar
"""

{FLAME.Pool,
 name: MyApp.SamplePool,
 backend: {FLAMEK8sBackend, manifest: manifest}}
```

--------------------------------

### RBAC Configuration for Service Account

Source: https://hexdocs.pm/flame_k8s_backend/readme.html

Define a ServiceAccount, Role, and RoleBinding to grant necessary permissions for managing pods. Ensure the `namespace` and `name` fields are correctly set for your application.

```yaml
---
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
```

--------------------------------

### Configure Environment Variables for Runners

Source: https://hexdocs.pm/flame_k8s_backend/readme.html

Set `POD_NAME` and `POD_NAMESPACE` environment variables in your deployment configuration. These are used by the backend to gather information about the pod and configure runner pods.

```yaml
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
```
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