kubernetes-client

Example

Load KubeConfig file

import Control.Concurrent.STM (atomically, newTVar)
import Kubernetes.Client      (KubeConfigSource (..), mkKubeClientConfig)
import Kubernetes.OpenAPI     (Accept (..), MimeJSON (..), dispatchMime)

import qualified Data.Map                      as Map
import qualified Kubernetes.OpenAPI.API.CoreV1 as CoreV1

main :: IO ()
main = do
    oidcCache <- atomically $ newTVar $ Map.fromList []
    (mgr, kcfg) <- mkKubeClientConfig oidcCache $ KubeConfigFile "/path/to/kubeconfig"
    dispatchMime
            mgr
            kcfg
            (CoreV1.listPodForAllNamespaces (Accept MimeJSON))
        >>= print

Load InCluster Config

import Control.Concurrent.STM (atomically, newTVar)
import Data.Function          ((&))
import Kubernetes.Client      (KubeConfigSource (..), mkKubeClientConfig)
import Kubernetes.OpenAPI     (Accept (..), MimeJSON (..), dispatchMime)
import Network.TLS            (credentialLoadX509)

import qualified Data.Map                      as Map
import qualified Kubernetes.OpenAPI.API.CoreV1 as CoreV1

main :: IO ()
main = do
    oidcCache <- atomically $ newTVar $ Map.fromList []
    (mgr, kcfg) <- mkKubeClientConfig oidcCache KubeConfigCluster
    dispatchMime
            mgr
            kcfg
            (CoreV1.listPodForAllNamespaces (Accept MimeJSON))
        >>= print

Load config from URL and paths

{-# LANGUAGE OverloadedStrings #-}

module Main where

import           Data.Function                 ((&))
import           Kubernetes.Client             (defaultTLSClientParams,
                                                disableServerCertValidation,
                                                disableServerNameValidation,
                                                disableValidateAuthMethods,
                                                loadPEMCerts, newManager,
                                                setCAStore, setClientCert,
                                                setMasterURI, setTokenAuth)
import           Kubernetes.OpenAPI            (Accept (..), MimeJSON (..),
                                                dispatchMime, newConfig)
import qualified Kubernetes.OpenAPI.API.CoreV1 as CoreV1
import           Network.TLS                   (credentialLoadX509)

main :: IO ()
main = do
    -- We need to first create a Kubernetes.Core.KubernetesConfig and a Network.HTTP.Client.Manager.
    -- Currently we need to construct these objects manually. Work is underway to construct these
    -- objects automatically from a kubeconfig file. See https://github.com/kubernetes-client/haskell/issues/2.
    kcfg <-
        newConfig
        & fmap (setMasterURI "https://mycluster.example.com")    -- fill in master URI
        & fmap (setTokenAuth "mytoken")                          -- if using token auth
        & fmap disableValidateAuthMethods                        -- if using client cert auth
    myCAStore <- loadPEMCerts "/path/to/ca.crt"                  -- if using custom CA certs
    myCert    <-                                                 -- if using client cert
        credentialLoadX509 "/path/to/client.crt" "/path/to/client.key"
            >>= either error return
    tlsParams <-
        defaultTLSClientParams
        & fmap disableServerNameValidation -- if master address is specified as an IP address
        & fmap disableServerCertValidation -- if you don't want to validate the server cert at all (insecure)
        & fmap (setCAStore myCAStore)      -- if using custom CA certs
        & fmap (setClientCert myCert)      -- if using client cert
    manager <- newManager tlsParams
    dispatchMime
            manager
            kcfg
            (CoreV1.listPodForAllNamespaces (Accept MimeJSON))
        >>= print

Watch Example

Following is a simple example which just streams to stdout. First some setup - this assumes kubernetes is accessible at http://localhost:8001, e.g. after running kubectl proxy:

> import qualified Data.ByteString.Streaming.Char8 as Q

> manager <- newManager defaultManagerSettings
> defaultConfig <- newConfig
> config = defaultConfig { configHost = "http://localhost:8001", configValidateAuthMethods = False }
> request = listEndpointsForAllNamespaces (Accept MimeJSON)

Launching 'dispatchWatch' with the above we get a stream of endpoints data:

 > dispatchWatch manager config request Q.stdout
 {"type":\"ADDED\","object":{"kind":\"Endpoints\","apiVersion":"v1","metadata":{"name":"heapster" ....

A more complex example involving some ggprocessing of the stream, the following prints out the event types of each event. First, define functions to allow us apply a parser to a stream:

import Data.Aeson 
import qualified Data.ByteString.Streaming.Char8 as Q
import Data.JsonStream.Parser
import qualified Streaming.Prelude as S

-- | Parse the stream using the given parser.
streamParse ::
  FromJSON a =>
    Parser a
    -> Q.ByteString IO r
    -> Stream (Of [a]) IO r
streamParse parser byteStream = do
  byteStream & Q.lines & parseEvent parser

-- | Parse a single event from the stream.
parseEvent ::
  (FromJSON a, Monad m) =>
    Parser a
    -> Stream (Q.ByteString m) m r
    -> Stream (Of [a]) m r
parseEvent parser byteStream = S.map (parseByteString parser) (S.mapped Q.toStrict byteStream)

Next, define the parser and apply it to the stream:

> eventParser = value :: Parser (WatchEvent V1Endpoints)
> withResponseBody body = streamParse eventParser body & S.map (map eventType)
> dispatchWatch manager config request (S.print . withResponseBody)
[\"ADDED\"]
[\"ADDED\"]
[\"MODIFIED\"]
...

Packages in this example:

• Data.Aeson -- from aeson
• Data.ByteString.Streaming.Char8 from streaming-bytestring
• Data.JsonStream.Parser from json-stream
• Streaming.Prelude from streaming