wrangling the internet of things with haskell production haskell - PowerPoint PPT Presentation

wrangling the internet of things with haskell production haskell Reid Draper @reiddraper

production haskell Reid Draper @reiddraper

production haskell today

production haskell at helium 12 months in

lowest defect rate

lowest defect rate easiest to refactor

lowest defect rate easiest to refactor most enjoyable OSS libraries for everything*

20k LOC

20k LOC 5 developers

20k LOC 5 developers 6 production services

build deploy monitor test develop

build deploy monitor test develop

cabal hell

cabal hell

stack haskellstack.org

ghc packages snapshot project specific

20k LOC 2 seconds

ordeal github.com/reiddraper/ordeal

stack build self-contained executable

build deploy monitor test develop

app ��� assets � ��� images � � ��� favicon.ico � ��� javascript � � ��� site.js � ��� stylesheet � ��� site.css ��� bin ��� app

tar -xzf app-370b347.tgz ln -s app-370b347 current restart app

ln -s app-83181ad current restart app

60MB

build deploy monitor test develop

ekg

stdout file syslog

build deploy monitor test develop

QuickCheck

propEvent :: Event -> Bool propEvent a = Just a == decode (encode a)

Event roundtrips in JSON: FAIL (0.04s) *** Failed! Falsifiable (after 1 test): Event {_severity = Error, _facility = Unspecified, _sampled = 1894-02-22 00:00:04.5986 UTC, _eventDetails = ElementDisconnect {_elementMAC = 8ec52584b2c82424}, _eventMessage = Nothing, _originator = http://www.ietf.org/rfc/rfc2396.txt, _reference = Just http://www.ietf.org/rfc/rfc2396.txt }

Event roundtrips in JSON: FAIL (0.04s) *** Failed! Falsifiable (after 1 test): Event {_severity = Error, _facility = Unspecified, _sampled = 1894-02-22 00:00:04.5986 UTC, _eventDetails = ElementDisconnect {_elementMAC = 8ec52584b2c82424}, _eventMessage = Nothing, _originator = http://www.ietf.org/rfc/rfc2396.txt, _reference = Just http://www.ietf.org/rfc/rfc2396.txt }

ghci> t 1894-02-22 00:00:04.5986 UTC ghci> Data.Aeson.encode t "\"1894-02-22T00:00:04.598Z\""

build deploy monitor test develop

postgresql-transactional github.com/helium/postgresql-transactional

lookupUser emailAddress = queryFirst [emailAddress] [sql| SELECT id, email, name, timezone FROM user_account 
 WHERE email = ? |]

foo

foo bar

foo bar baz

quz foo bar baz

quz foo bar baz buz

fiz quz foo bar baz buz

BEGIN BEGIN COMMIT COMMIT

BEGIN BEGIN COMMIT COMMIT

BEGIN BEGIN COMMIT COMMIT

WARNING: there is already a transaction in progress WARNING: there is no transaction in progress

fiz quz foo bar baz buz

fiz quz foo bar baz buz

quz foo bar baz buz

lookupUser :: Connection -> Text -> IO (Maybe User) lookupUser connection emailAddress = queryFirst [emailAddress] [sql| SELECT id, email, name, timezone FROM user_account 
 WHERE email = ? |] connection

createUser :: Connection -> NewUser -> IO User createOrganization :: Connection -> NewOrganization -> IO Organization addUserToOrganization :: Connection -> User -> Organization -> IO ()

createUserAndOrganization :: Connection -> NewUser -> IO () createUserAndOrganization connection newUser = withTransaction connection $ do let newOrganization = NewOrganization (newUser ^. name) user <- createUser connection newUser org <- createOrganization connection newOrganization addUserToOrganization connection user org

-- NOTE: you MUST wrap this in a transaction!! createUserAndOrganization :: Connection -> NewUser -> IO () createUserAndOrganization connection newUser = do let newOrganization = NewOrganization (newUser ^. name) user <- createUser connection newUser org <- createOrganization connection newOrganization addUserToOrganization connection user org

withTransaction conn $ do createUserAndOrganization conn newUser somethingElse conn

types to the rescue

lookupUser :: Connection -> Text -> IO (Maybe User) lookupUser :: Text -> PGTransaction (Maybe User)

runPGTransaction :: PGTransaction a -> Postgres.Connection -> IO a

createUserAndOrganization :: NewUser -> PGTransaction () createUserAndOrganization newUser = let newOrganization = NewOrganization (newUser ^. name) user <- createUser newUser org <- createOrganization newOrganization addUserToOrganization user org foo = do createUserAndOrganization newUser somethingElse runPGTransaction foo connection

notAllowed = do user <- createUser newUser someSlowSideEffectingThing return user

notAllowed = do user <- createUser newUser someSlowSideEffectingThing :: IO () return user

postgresql-transactional github.com/helium/postgresql-transactional

build deploy monitor test develop

Reid Draper @reiddraper github.com/helium helium.com