Safe Haskell	Safe-Inferred
Language	GHC2021

Stamina

Synopsis

retry :: forall m a. (MonadCatch m, MonadIO m) => RetrySettings -> (RetryStatus -> m a) -> m a
retryFor :: forall m exc a. (Exception exc, MonadIO m, MonadCatch m) => RetrySettings -> (exc -> m RetryAction) -> (RetryStatus -> m a) -> m a
data RetrySettings = RetrySettings {
- initialRetryStatus :: RetryStatus
- maxAttempts :: Maybe Int
- maxTime :: Maybe NominalDiffTime
- backoffMaxRetryDelay :: Maybe NominalDiffTime
- backoffJitter :: Double
- backoffExpBase :: Double
}
defaults :: RetrySettings
indefiniteDefaults :: RetrySettings
data RetryAction
- = RaiseException
- | Retry
- | RetryDelay NominalDiffTime
- | RetryTime UTCTime
data RetryStatus = RetryStatus {
- attempts :: Int
- delay :: NominalDiffTime
- totalDelay :: NominalDiffTime
- resetInitial :: IO ()
- lastException :: Maybe SomeException
}
escalateWith :: Exception exc => (err -> exc) -> Either err a -> IO a
escalate :: Exception exc => Either exc a -> IO a
withLeft :: a -> Maybe b -> Either a b

Documentation

retry :: forall m a. (MonadCatch m, MonadIO m) => RetrySettings -> (RetryStatus -> m a) -> m a Source #

Retry on all sync exceptions, async exceptions will still be thrown.

The backoff delays between retries grow exponentially plus a random jitter. The backoff for retry attempt number _attempt_ is computed as:

   backoffExpBase ** (attempt - 1) + random(0, backoffJitter)

With the default values, the backoff for the first 5 attempts will be:

   2 ** 0 + random(0, 1) = 1 + random(0, 1)
   2 ** 1 + random(0, 1) = 2 + random(0, 1)
   2 ** 2 + random(0, 1) = 4 + random(0, 1)
   2 ** 3 + random(0, 1) = 8 + random(0, 1)
   2 ** 4 + random(0, 1) = 16 + random(0, 1)

If all retries fail, the last exception is let through.

retryFor :: forall m exc a. (Exception exc, MonadIO m, MonadCatch m) => RetrySettings -> (exc -> m RetryAction) -> (RetryStatus -> m a) -> m a Source #

data RetrySettings Source #

Settings for the retry functions.

Constructors

RetrySettings

Fields

initialRetryStatus :: RetryStatus
Initial status of the retry, useful to override when resuming a retry
maxAttempts :: Maybe Int
Maximum number of attempts. Can be combined with a timeout. Default to 10.
maxTime :: Maybe NominalDiffTime
Maximum time for all retries. Can be combined with attempts. Default to 60s.
backoffMaxRetryDelay :: Maybe NominalDiffTime
Maximum backoff between retries at any time. Default to 60s.
backoffJitter :: Double
Maximum jitter that is added to retry back-off delays (the actual jitter added is a random number between 0 and backoffJitter). Defaults to 1.0.
backoffExpBase :: Double
The exponential base used to compute the retry backoff. Defaults to 2.0.

defaults :: RetrySettings Source #

indefiniteDefaults :: RetrySettings Source #

data RetryAction Source #

Constructors

RaiseException
Retry
RetryDelay NominalDiffTime
RetryTime UTCTime

Instances

Instances details

Show RetryAction Source #
Instance details Defined in Stamina Methods showsPrec :: Int -> RetryAction -> ShowS # show :: RetryAction -> String # showList :: [RetryAction] -> ShowS #
Eq RetryAction Source #
Instance details Defined in Stamina Methods (==) :: RetryAction -> RetryAction -> Bool # (/=) :: RetryAction -> RetryAction -> Bool #

data RetryStatus Source #

Tracks the status of a retry

All fields will be zero if no retries have been attempted yet.

Constructors

RetryStatus
Fields attempts :: Int Number of retry attempts so far. delay :: NominalDiffTime Delay before the next retry. totalDelay :: NominalDiffTime Total delay so far. resetInitial :: IO () Reset the retry status to the initial state. lastException :: Maybe SomeException The last exception that was thrown.

escalateWith :: Exception exc => (err -> exc) -> Either err a -> IO a Source #

Escalate an Either to an exception by converting the Left value to an exception.

escalate :: Exception exc => Either exc a -> IO a Source #

Escalate an Either to an exception.

withLeft :: a -> Maybe b -> Either a b Source #

Convert a Maybe to an Either.