Database.PostgreSQL.Resilient

The withResilientConnection function gives us a ResilientConnection from which we can always get a health connection, while automatic reconnection with retries and exponential back-offs are being handled in the background.

import           Database.PostgreSQL.Resilient
import qualified Database.PostgreSQL.Simple    as P

withResilientConnection defaultResilientSettings logHandler connectInfo $ pool ->
  (conn :: P.Connection) <- getConnection pool
  res <- P.query_ conn "SELECT * FROM foo"
  putStrLn $ show res

logHandler :: String -> IO ()
logHandler = putStrLn

connectInfo :: P.ConnectInfo
connectInfo = P.ConnectInfo
  { P.connectHost     = "localhost"
  , P.connectPort     = 5432
  , P.connectUser     = "postgres"
  , P.connectPassword = ""
  , P.connectDatabase = "store"
  }

defaultResilientSettings :: ResilientSettings
defaultResilientSettings = ResilientSettings
  { healthCheckEvery     = 3
  , exponentialBackoffThreshold = 10
  }

Documentation

data ResilientConnection m

Single connection pool with built-in reconnection

Constructors

ResilientConnection

Fields

• getConnection :: m Connection

  Get the latest healthy connection.

data ResilientSettings

The resilient settings

Constructors

ResilientSettings

Fields

• healthCheckEvery :: Seconds

  How often to check the connection status.

• exponentialBackoffThreshold :: Seconds

  After this threshold, stop the exponential back-off.

Instances

Show ResilientSettings

Defined in Database.PostgreSQL.Resilient

Methods

showsPrec :: Int -> ResilientSettings -> ShowS

show :: ResilientSettings -> String

showList :: [ResilientSettings] -> ShowS

data Seconds

Represents amount of seconds

Instances

Eq Seconds

Defined in Database.PostgreSQL.Resilient

Methods

(==) :: Seconds -> Seconds -> Bool

(/=) :: Seconds -> Seconds -> Bool

Num Seconds

Defined in Database.PostgreSQL.Resilient

Methods

(+) :: Seconds -> Seconds -> Seconds

(-) :: Seconds -> Seconds -> Seconds

(*) :: Seconds -> Seconds -> Seconds

negate :: Seconds -> Seconds

abs :: Seconds -> Seconds

signum :: Seconds -> Seconds

fromInteger :: Integer -> Seconds

Ord Seconds

Defined in Database.PostgreSQL.Resilient

Methods

compare :: Seconds -> Seconds -> Ordering

(<) :: Seconds -> Seconds -> Bool

(<=) :: Seconds -> Seconds -> Bool

(>) :: Seconds -> Seconds -> Bool

(>=) :: Seconds -> Seconds -> Bool

max :: Seconds -> Seconds -> Seconds

min :: Seconds -> Seconds -> Seconds

Show Seconds

Defined in Database.PostgreSQL.Resilient

Methods

showsPrec :: Int -> Seconds -> ShowS

show :: Seconds -> String

showList :: [Seconds] -> ShowS

withResilientConnection :: forall a. ResilientSettings -> LogHandler -> ConnectInfo -> (ResilientConnection IO -> IO a) -> IO a

Returns a ResilientConnection from which you can always acquire the latest connection available. - - Reconnections with configurable retries and exponential back-offs as well as closing the connection once done using it (guaranteed by bracket) are too handled by this function. -

defaultResilientSettings :: ResilientSettings

Default resilient settings