propellor/Propellor/Property/Docker.hs

{-# LANGUAGE RankNTypes #-}

-- | Docker support for propellor
--
-- The existance of a docker container is just another Property of a system,
-- which propellor can set up. See config.hs for an example.
--
-- Note that propellor provisions a container by running itself, inside the
-- container. Currently, to avoid the overhead of building propellor
-- inside the container, the binary from outside is reused inside. 
-- So, the libraries that propellor is linked against need to be available
-- in the container with compatable versions. This can cause a problem
-- if eg, mixing Debian stable and unstable.

module Propellor.Property.Docker where

import Propellor
import Propellor.SimpleSh
import qualified Propellor.Property.File as File
import qualified Propellor.Property.Apt as Apt
import Utility.SafeCommand
import Utility.Path

import Control.Concurrent.Async
import System.Posix.Directory

dockercmd :: String
dockercmd = "docker.io"

-- | Configures docker with an authentication file, so that images can be
-- pushed to index.docker.io.
configured :: Property
configured = Property "docker configured" go `requires` installed
  where
	go = withPrivData DockerAuthentication $ \cfg -> ensureProperty $ 
		"/root/.dockercfg" `File.hasContent` (lines cfg)

installed :: Property
installed = Apt.installed ["docker.io"]

-- | Parameters to pass to `docker run` when creating a container.
type RunParam = String

data Containerized a = Containerized [RunParam] a

getRunParams :: [Containerized a] -> [RunParam]
getRunParams l = concatMap get l
  where
	get (Containerized ps _) = ps

fromContainerized :: forall a. [Containerized a] -> [a]
fromContainerized l = map get l
  where
	get (Containerized _ a) = a

-- | A docker image, that can be used to run a container.
type Image = String

-- | A short descriptive name for a container.
-- Should not contain whitespace or other unusual characters,
-- only [a-zA-Z0-9_.-] are allowed
type ContainerName = String

-- | A container is identified by its name, and the host
-- on which it's deployed.
data ContainerId = ContainerId HostName ContainerName
	deriving (Eq)

toContainerId :: String -> Maybe ContainerId
toContainerId s = case separate (== '.') s of
	(cn, hn)
		| null hn || null cn -> Nothing
		| otherwise -> Just $ ContainerId hn cn

fromContainerId :: ContainerId -> String
fromContainerId (ContainerId hn cn) = cn++"."++hn

data Container = Container Image [Containerized Property]

containerFrom :: Image -> [Containerized Property] -> Container
containerFrom = Container

containerProperties
	:: (HostName -> ContainerName -> Maybe (Container))
	-> (HostName -> Maybe [Property])
containerProperties findcontainer = \h -> case toContainerId h of
	Nothing -> Nothing
	Just cid@(ContainerId hn cn) ->
		case findcontainer hn cn of
			Nothing -> Nothing
			Just (Container _ cprops) -> 
				Just $ map (containerDesc cid) $
					fromContainerized cprops

containerDesc :: ContainerId -> Property -> Property
containerDesc cid p = p `describe` desc
  where
	desc = "[" ++ fromContainerId cid ++ "] " ++ propertyDesc p

-- | Ensures that a docker container is set up and running. The container
-- has its own Properties which are handled by running propellor
-- inside the container.
docked
	:: (HostName -> ContainerName -> Maybe (Container))
	-> HostName
	-> ContainerName
	-> Property
docked findcontainer hn cn = 
	case findcontainer hn cn of
		Nothing -> containerDesc cid $ Property "" $ do
			warningMessage $ "missing definition for docker container \"" ++ fromContainerId cid
			return FailedChange
		Just (Container image containerprops) ->
			provisionContainer cid
				`requires`
			runningContainer cid image containerprops
  where
  	cid = ContainerId hn cn

runningContainer :: ContainerId -> Image -> [Containerized Property] -> Property
runningContainer cid@(ContainerId hn cn) image containerprops = containerDesc cid $ Property "running" $ do
	l <- listContainers RunningContainers
	if cid `elem` l
		then do
			runningident <- getrunningident
			if ident2id <$> runningident == Just (ident2id ident)
				then return NoChange
				else do
					void $ stopContainer cid
					oldimage <- fromMaybe image <$> commitContainer cid
					removeContainer cid
					go oldimage
		else do
			whenM (elem cid <$> listContainers AllContainers) $
				removeContainer cid
			go image
  where
	ident = ContainerIdent image hn cn runps

	getrunningident = catchDefaultIO Nothing $
		simpleShClient (namedPipe cid) "cat" [propellorIdent] $
			pure . headMaybe . catMaybes . map readish . catMaybes . map getStdout

	runps = getRunParams $ containerprops ++
		-- expose propellor directory inside the container
		[ volume (localdir++":"++localdir)
		-- name the container in a predictable way so we
		-- and the user can easily find it later
		, name (fromContainerId cid)
		]
	
	chaincmd = [localdir </> "propellor", "--continue", show $ ChainDocker $ show ident]

	go img = ifM (runContainer img (runps ++ ["-i", "-d", "-t"]) chaincmd)
		( return MadeChange
		, return FailedChange
		)

-- | Two containers with the same ContainerIdent were started from
-- the same base image (possibly a different version though), and
-- with the same RunParams.
data ContainerIdent = ContainerIdent Image HostName ContainerName [RunParam]
	deriving (Read, Show, Eq)

ident2id :: ContainerIdent -> ContainerId
ident2id (ContainerIdent _ hn cn _) = ContainerId hn cn

-- | The ContainerIdent of a container is written to
-- /.propellor-ident inside it. This can be checked to see if
-- the container has the same ident later.
propellorIdent :: FilePath
propellorIdent = "/.propellor-ident"

-- | Named pipe used for communication with the container.
namedPipe :: ContainerId -> FilePath
namedPipe cid = "docker/" ++ fromContainerId cid

-- | Called when propellor is running inside a docker container.
-- The string should be the container's ContainerIdent.
--
-- Fork a thread to run the SimpleSh server in the background.
-- In the foreground, run an interactive bash (or sh) shell,
-- so that the user can interact with it when attached to the container.
chain :: String -> IO ()
chain s = case readish s of
	Nothing -> error $ "Invalid ContainerId: " ++ s
	Just ident@(ContainerIdent _image hn cn _rp) -> do
		changeWorkingDirectory localdir
		let cid = ContainerId hn cn
		writeFile propellorIdent (show ident)
		void $ async $ simpleSh $ namedPipe cid
		forever $ do
			void $ ifM (inPath "bash")
				( boolSystem "bash" [Param "-l"]
				, boolSystem "/bin/sh" []
				)
			putStrLn "Container is still running. Press ^P^Q to detach."

-- | Once a container is running, propellor can be run inside
-- it to provision it.
--
-- Note that there is a race here, between the simplesh
-- server starting up in the container, and this property
-- being run. So, retry connections to the client for up to
-- 1 minute.
provisionContainer :: ContainerId -> Property
provisionContainer cid = containerDesc cid $ Property "provision" $
	simpleShClientRetry 60 (namedPipe cid) "./propellor" params (go Nothing)
  where
	params = ["--continue", show $ Chain $ fromContainerId cid]

	go lastline (v:rest) = case v of
		StdoutLine s -> do
			debug ["stdout: ", show s]
			maybe noop putStrLn lastline
			hFlush stdout
			go (Just s) rest
		StderrLine s -> do
			debug ["stderr: ", show s]
			maybe noop putStrLn lastline
			hFlush stdout
			hPutStrLn stderr s
			hFlush stderr
			go Nothing rest
		Done _ -> ret lastline
	go lastline [] = ret lastline

	ret lastline = return $ fromMaybe FailedChange $
		readish =<< lastline

stopContainer :: ContainerId -> IO Bool
stopContainer cid = boolSystem dockercmd [Param "stop", Param $ fromContainerId cid ]

removeContainer :: ContainerId -> IO ()
removeContainer cid = void $ catchMaybeIO $
	readProcess dockercmd ["rm", fromContainerId cid ]

runContainer :: Image -> [RunParam] -> [String] -> IO Bool
runContainer image ps cmd = boolSystem dockercmd $ map Param $
	"run" : (ps ++ image : cmd)

commitContainer :: ContainerId -> IO (Maybe Image)
commitContainer cid = catchMaybeIO $
	takeWhile (/= '\n') 
		<$> readProcess dockercmd ["commit", fromContainerId cid]

data ContainerFilter = RunningContainers | AllContainers
	deriving (Eq)

-- | Only lists propellor managed containers.
listContainers :: ContainerFilter -> IO [ContainerId]
listContainers status = 
	catMaybes . map toContainerId . catMaybes . map (lastMaybe . words) . lines
		<$> readProcess dockercmd ps
  where
	ps
		| status == AllContainers = baseps ++ ["--all"]
		| otherwise = baseps
	baseps = ["ps", "--no-trunc"]

runProp :: String -> RunParam -> Containerized Property
runProp field val = 
	Containerized ["--" ++ param] (Property (param) (return NoChange))
  where
	param = field++"="++val

-- | Lift a Property to run inside the container.
inside1 :: Property -> Containerized Property
inside1 = Containerized []

inside :: [Property] -> Containerized Property
inside = Containerized [] . combineProperties "provision"

-- | Set custom dns server for container.
dns :: String -> Containerized Property
dns = runProp "dns"

-- | Set container host name.
hostname :: String -> Containerized Property
hostname = runProp "hostname"

-- | Set name for container. (Normally done automatically.)
name :: String -> Containerized Property
name = runProp "name"

-- | Publish a container's port to the host
-- (format: ip:hostPort:containerPort | ip::containerPort | hostPort:containerPort)
publish :: String -> Containerized Property
publish = runProp "publish"

-- | Username or UID for container.
user :: String -> Containerized Property
user = runProp "user"

-- | Bind mount a volume
volume :: String -> Containerized Property
volume = runProp "volume"

-- | Work dir inside the container. 
workdir :: String -> Containerized Property
workdir = runProp "workdir"

-- | Memory limit for container.
--Format: <number><optional unit>, where unit = b, k, m or g
memory :: String -> Containerized Property
memory = runProp "memory"