Stamina: Haskell library for retries

As we deal with networking and databases in our day-to-day work, Haskell exceptions frequently arise in our code.

We’ve been using the Haskell retry package for retrying exceptions so far, but it presents several issues:

• The API is cumbersome to remember, so we’ve always built a thin layer on top.
• It lacks built-in support for retrying HTTP exceptions, which requires careful selection of retryable instances and adherence to the retry-after header.
• To log the exception that occurred, one needs to write a logger as an exception handler.
• It’s not possible to reset the retry state when a long-lived task (such as a WebSocket connection) finally succeeds.

Heavily inspired by Hynek’s Stamina for Python, we’re releasing Stamina for Haskell:

• Exponential backoff with random jitter between retries.
• Limit the attempts of retries and total time.
• Stamina.HTTP for retrying retriable Network.HTTP.Client exceptions respecting Retry-After header.
• Introspectable retry state for logging using RetryStatus, including the last exception that occurred.
• Supports resetting the retry state for long-running tasks whenever a retry attempt succeeds.

Basic example

import qualified Stamina
import Control.Monad.Catch (throwM)

go :: IO ()
go = Stamina.retry Stamina.defaults $ \retryStatus -> do
  print $ show $ Stamina.lastException retryStatus
  throwM $ userError "nope"

For more examples see README.md.

Domen