shrub/pkg/hs/urbit-king/lib/Urbit/Vere/Eyre/Service.hs

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{-|
Eyre: Http Server Driver
-}
module Urbit.Vere.Eyre.Service
( restartService
, stopService
)
where
import Urbit.Prelude
-- Generic Service Stop/Restart -- Using an MVar for Atomicity -----------------
{-|
Restart a running service.
This can probably be made simpler, but it
- Sets the MVar to Nothing if there was an exception while starting
or stopping the service.
- Keeps the MVar lock until the restart process finishes.
-}
restartService
:: forall e s
. HasLogFunc e
=> MVar (Maybe s)
-> RIO e s
-> (s -> RIO e ())
-> RIO e (Either SomeException s)
restartService vServ sstart kkill = do
logDebug "restartService"
modifyMVar vServ $ \case
Nothing -> doStart
Just sv -> doRestart sv
where
doRestart :: s -> RIO e (Maybe s, Either SomeException s)
doRestart serv = do
logDebug "doStart"
try (kkill serv) >>= \case
Left exn -> pure (Nothing, Left exn)
Right () -> doStart
doStart :: RIO e (Maybe s, Either SomeException s)
doStart = do
logDebug "doStart"
try sstart <&> \case
Right s -> (Just s, Right s)
Left exn -> (Nothing, Left exn)
{-|
Stop a running service. Do nothing if it's already stopped.
-}
stopService
:: HasLogFunc e
=> MVar (Maybe s)
-> (s -> RIO e ())
-> RIO e (Either SomeException ())
stopService vServ kkill = do
logDebug "stopService"
modifyMVar vServ $ \case
Nothing -> pure (Nothing, Right ())
Just sv -> do
res <- try (kkill sv)
pure (Nothing, res)