k8s v2.2.0

View Source HTTP Operations (K8s.Operation)

K8s.Operations are Kubernetes REST operations. They encapsulate all the details of an HTTP request except the server to perform them against.

Many more client examples exist in the K8s.Client docs.

creating-a-deployment-from-a-map

 Creating a Deployment from a Map 

resource = %{
  "apiVersion" => "apps/v1",
  "kind" => "Deployment",
  "metadata" => %{
    "labels" => %{"app" => "nginx"},
    "name" => "nginx-deployment",
    "namespace" => "default"
  },
  "spec" => %{
    "replicas" => 3,
    "selector" => %{"matchLabels" => %{"app" => "nginx"}},
    "template" => %{
      "metadata" => %{"labels" => %{"app" => "nginx"}},
      "spec" => %{
        "containers" => [
          %{
            "image" => "nginx:1.7.9",
            "name" => "nginx",
            "ports" => [%{"containerPort" => 80}]
          }
        ]
      }
    }
  }
}

operation = K8s.Client.create(resource)
{:ok, conn} = K8s.Conn.from_file("path/to/kubeconfig.yaml")
{:ok, response} = K8s.Client.run(conn, operation)

creating-a-deployment-from-a-yaml-file

 Creating a Deployment from a YAML File

K8s.Resource provides YAML resource parsing and interpolation support as well as a few helper functions for accessing common Kubernetes resource fields.

Given the YAML file priv/deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: <%= name %>-deployment
  namespace: <%= namespace %>
  labels:
    app: <%= name %>
spec:
  replicas: 3
  selector:
    matchLabels:
      app: <%= name %>
  template:
    metadata:
      labels:
        app: <%= name %>
    spec:
      containers:
        - name: <%= name %>
          image: <%= image %>
          ports:
            - containerPort: 80
opts = [namespace: "default", name: "nginx", image: "nginx:nginx:1.7.9"]
resource = K8s.Resource.from_file!("priv/deployment.yaml", opts)

operation = K8s.Client.create(resource)
{:ok, conn} = K8s.Conn.from_file("path/to/kubeconfig.yaml")
{:ok, deployment} = K8s.Client.run(conn, operation)

listing-deployments

 Listing Deployments

In a given namespace:

operation = K8s.Client.list("apps/v1", "Deployment", namespace: "prod")
{:ok, conn} = K8s.Conn.from_file("path/to/kubeconfig.yaml")
{:ok, deployments} = K8s.Client.run(conn, operation)

Across all namespaces:

operation = K8s.Client.list("apps/v1", "Deployment", namespace: :all)
{:ok, conn} = K8s.Conn.from_file("path/to/kubeconfig.yaml")
{:ok, deployments} = K8s.Client.run(conn, operation)

Note: K8s.Client.list will return a map. The list of resources will be under "items".

using-labelselector-with-list-operations

 Using labelSelector with List Operations

K8s.Selector supports programatically building Kubernetes labelSelectors.

{:ok, conn} = K8s.Conn.from_file("path/to/kubeconfig.yaml")

operation =
  K8s.Client.list("apps/v1", :deployments)
  |> K8s.Selector.label({"app", "nginx"})
  |> K8s.Selector.label_in({"environment", ["qa", "prod"]})

K8s.Client.run(conn, operation)

getting-a-deployment

 Getting a Deployment 

{:ok, conn} = K8s.Conn.from_file("path/to/kubeconfig.yaml")
operation = K8s.Client.get("apps/v1", :deployment, [namespace: "default", name: "nginx-deployment"])
{:ok, deployment} = K8s.Client.run(conn, operation)

watch-operations-k8s-client-runner-watch

 Watch Operations (K8s.Client.Runner.Watch)

Watch operations use the Kubernetes Watch API to stream added, modified, and deleted as they occur.

To get a stream of events:

operation = K8s.Client.watch("apps/v1", :deployment, namespace: :all)
{:ok, conn} = K8s.Conn.from_file("path/to/kubeconfig.yaml")
{:ok, event_stream} = K8s.Client.stream(conn, operation)

wait-on-a-resource-k8s-client-runner-wait

 Wait on a Resource (K8s.Client.Runner.Wait)

The wait runner permits read operations to be made and block until a certain state is met in Kubernetes.

This follow example will wait 60 seconds for the field status.succeeded to equal 1.

operation = K8s.Client.get("batch/v1", :job, namespace: "default", name: "database-migrator")
wait_opts = [find: ["status", "succeeded"], eval: 1, timeout: 60]
{:ok, conn} = K8s.Conn.from_file("path/to/kubeconfig.yaml")
{:ok, job} = K8s.Client.wait_until(conn, operation, wait_opts)

:find and :eval also accept functions to apply to check success.

async-batch-operations-k8s-client-runner-async

 Async Batch Operations (K8s.Client.Runner.Async)

An async runner is provided for running operations in parallel. All operations are fired async and their results are returned. Processing does not halt if an error occurs for one operation.

operation1 = K8s.Client.get("v1", "Pod", namespace: "default", name: "pod-1")
operation2 = K8s.Client.get("v1", "Pod", namespace: "default", name: "pod-2")

{:ok, conn} = K8s.Conn.from_file("path/to/kubeconfig.yaml")
results = K8s.Client.async(conn, [operation1, operation2])

results will be a list of :ok and :error tuples.

list-operations-as-elixir-streams-k8s-client-runner-stream

 List Operations as Elixir Streams (K8s.Client.Runner.Stream)

A stream runner is provided to automatically handle pagination in K8s.Client.list/3 operations.

operation = K8s.Client.list("v1", "Pod", namespace: :all)
{:ok, conn} = K8s.Conn.from_file("path/to/kubeconfig.yaml")

conn
|> K8s.Client.stream(operation)
|> Stream.filter(&my_filter_function?/1)
|> Stream.map(&my_map_function?/1)
|> Enum.into([])

connect-to-pods-and-execute-commands

 Connect to pods and execute commands

The :connect operation is used to connect to pods and execute commands. A :connect operation is created with K8s.Client.connect/N. Be sure to pass the command you want to run in the options.

waiting-for-command-termination

 Waiting for command termination

If you want to run a command that terminates and wait for it, pass the :connect operation to K8s.Client.run/N.

  {:ok, conn} = K8s.Conn.from_file("~/.kube/config")

  op = K8s.Client.connect(
    "v1",
    "pods/exec",
    [namespace: "default", name: "nginx-8f458dc5b-zwmkb"],
    command: ["/bin/sh", "-c", "nginx -t"]
  )

  {:ok, response} = K8s.Client.run(conn, op)

opening-long-lasting-connections-e-g-a-shell-and-sending-messages-to-pods

 Opening long-lasting connections (e.g. a shell) and sending messages to pods

If you send a command that does not terminate (e.g. /bin/sh) or one that takes long to terminate, you can open the connection in a separate process and stream the response. Further, you can send/2 messages to that process (e.g. further commands). See the example below.

  {:ok, conn} = K8s.Conn.from_file("~/.kube/config")

  op = K8s.Client.connect(
    "v1",
    "pods/exec",
    [namespace: "default", name: "nginx-8f458dc5b-zwmkb"],
    command: ["/bin/sh"]
  )

  parent_process = self()

  task = Task.async(fn ->
    {:ok, stream} = K8s.Client.stream(conn, op)

    stream
    |> Stream.map(&send(parent_process, &1))
    |> Stream.run()
  end)

  # wait for connection to be established
  receive(do: (:open -> :ok)

  send(task.pid, {:stdin, ~s(echo "hello world"\n)})

  # you receive "hello world" on stdout
  receive(do: ({:stdout, message} -> IO.puts(message))

  # close the connection, the task will terminate.
  send(task.pid, :close)

options

 Options

  • command - required for running commands
  • container - if a pod runs multiple containers, you have to specify the container to run the command in.
  • stdin - enable stdin (defaults to true)
  • stdout - enable stdout (defaults to true)
  • stderr - enable stderr (defaults to true)
  • tty - stdin is a TTY (defaults to false)
  {:ok, conn} = K8s.Conn.from_file("~/.kube/config")

  op = K8s.Client.connect(
    "v1",
    "pods/exec",
    [namespace: "default", name: "nginx-8f458dc5b-zwmkb"],
    command: ["/bin/sh", "-c", "nginx -t"],
    container: "main",
    tty: true
  )

  {:ok, response} = K8s.Client.run(conn, op)