move TransferrerPool from assistant

This old code will now be useful for git-annex beyond the assistant.

git-annex won't use the CheckTransferrer part, and won't run transferkeys
as a batch process, and will want withTransferrer to not shut down
transferkeys processes. Still, the rest of this is a good fit for what I
need now.

Also removed some dead code, and simplified a little bit.

This commit was sponsored by Mark Reidenbach on Patreon.

Annex/TransferrerPool.hs

@@ -1,42 +1,46 @@
 {- A pool of "git-annex transferkeys" processes
  -
- - Copyright 2013 Joey Hess <id@joeyh.name>
+ - Copyright 2013-2020 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
-module Assistant.TransferrerPool where
+{-# LANGUAGE RankNTypes #-}
 
-import Assistant.Common
-import Assistant.Types.TransferrerPool
+module Annex.TransferrerPool where
+
+import Annex.Common
+import Types.TransferrerPool
 import Types.Transfer
 import Utility.Batch
 import Messages.Serialized
-
 import qualified Command.TransferKeys as T
 
 import Control.Concurrent.STM hiding (check)
-import Control.Exception (throw)
 import Control.Concurrent
+import Control.Monad.IO.Class (MonadIO)
 
 {- Runs an action with a Transferrer from the pool.
  -
- - Only one Transferrer is left running in the pool at a time.
- - So if this needed to start a new Transferrer, it's stopped when done.
+ - When minimizeprocesses is True, only one Transferrer is left running
+ - in the pool at a time. So if this needed to start a new Transferrer,
+ - it's stopped when done. Otherwise, idle processes are left in the pool
+ - for use later.
  -}
-withTransferrer :: FilePath -> BatchCommandMaker -> TransferrerPool -> (Transferrer -> IO a) -> IO a
-withTransferrer program batchmaker pool a = do
+withTransferrer :: Bool -> FilePath -> BatchCommandMaker -> TransferrerPool -> (Transferrer -> IO a) -> IO a
+withTransferrer minimizeprocesses program batchmaker pool a = do
 	(mi, leftinpool) <- atomically (popTransferrerPool pool)
 	i@(TransferrerPoolItem (Just t) check) <- case mi of
 		Nothing -> mkTransferrerPoolItem pool =<< mkTransferrer program batchmaker
 		Just i -> checkTransferrerPoolItem program batchmaker i
-	v <- tryNonAsync $ a t
-	if leftinpool == 0
-		then atomically $ pushTransferrerPool pool i
-		else do
+	a t `finally` returntopool leftinpool check t i
+  where
+	returntopool leftinpool check t i
+		| not minimizeprocesses || leftinpool == 0 =
+			atomically $ pushTransferrerPool pool i
+		| otherwise = do
 			void $ forkIO $ stopTransferrer t
 			atomically $ pushTransferrerPool pool $ TransferrerPoolItem Nothing check
-	either throw return v
 
 {- Check if a Transferrer from the pool is still ok to be used.
  - If not, stop it and start a new one. -}
@@ -56,13 +60,21 @@ checkTransferrerPoolItem program batchmaker i = case i of
 
 {- Requests that a Transferrer perform a Transfer, and waits for it to
  - finish. -}
-performTransfer :: Transferrer -> Transfer -> TransferInfo -> Assistant Bool
-performTransfer transferrer t info = catchBoolIO $ do
+performTransfer
+	:: (Monad m, MonadIO m, MonadMask m)
+	=> Transferrer
+	-> Transfer
+	-> TransferInfo
+	-> (forall a. Annex a -> m a)
+	-- ^ Run an annex action in the monad. Will not be used with
+	-- actions that block for a long time.
+	-> m Bool
+performTransfer transferrer t info runannex = catchBoolIO $ do
 	(liftIO $ T.sendRequest t info (transferrerWrite transferrer))
 	relaySerializedOutput
 		(liftIO $ T.readResponse (transferrerRead transferrer))
 		(liftIO . T.sendSerializedOutputResponse (transferrerWrite transferrer))
-		liftAnnex
+		runannex
 
 {- Starts a new git-annex transferkeys process, setting up handles
  - that will be used to communicate with it. -}
@@ -84,13 +96,8 @@ mkTransferrer program batchmaker = do
 		, transferrerHandle = pid
 		}
 
-{- Checks if a Transferrer is still running. If not, makes a new one. -}
-checkTransferrer :: FilePath -> BatchCommandMaker -> Transferrer -> IO Transferrer
-checkTransferrer program batchmaker t =
-	maybe (return t) (const $ mkTransferrer program batchmaker)
-		=<< getProcessExitCode (transferrerHandle t)
-
-{- Closing the fds will stop the transferrer. -}
+{- Closing the fds will stop the transferrer, but only when it's in between
+ - transfers. -}
 stopTransferrer :: Transferrer -> IO ()
 stopTransferrer t = do
 	hClose $ transferrerRead t

Assistant/TransferSlots.hs

@@ -13,7 +13,7 @@ import Assistant.Common
 import Utility.ThreadScheduler
 import Assistant.Types.TransferSlots
 import Assistant.DaemonStatus
-import Assistant.TransferrerPool
+import Annex.TransferrerPool
 import Assistant.Types.TransferrerPool
 import Assistant.Types.TransferQueue
 import Assistant.TransferQueue
@@ -83,7 +83,7 @@ runTransferThread' :: FilePath -> BatchCommandMaker -> AssistantData -> (Transfe
 runTransferThread' program batchmaker d run = go
   where
 	go = catchPauseResume $
-		withTransferrer program batchmaker (transferrerPool d)
+		withTransferrer True program batchmaker (transferrerPool d)
 			run
 	pause = catchPauseResume $
 		runEvery (Seconds 86400) noop
@@ -155,7 +155,7 @@ genTransfer t info = case transferRemote info of
 	 - usual cleanup. However, first check if something else is
 	 - running the transfer, to avoid removing active transfers.
 	 -}
-	go remote transferrer = ifM (performTransfer transferrer t info)
+	go remote transferrer = ifM (performTransfer transferrer t info liftAnnex)
 		( do
 			case associatedFile info of
 				AssociatedFile Nothing -> noop

Assistant/Types/TransferrerPool.hs

@@ -5,57 +5,16 @@
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
-module Assistant.Types.TransferrerPool where
+module Assistant.Types.TransferrerPool (
+	module Types.TransferrerPool,
+	checkNetworkConnections,
+) where
 
-import Annex.Common
+import Types.TransferrerPool
 import Utility.NotificationBroadcaster
 import Assistant.Types.DaemonStatus
 
-import Control.Concurrent.STM hiding (check)
-
-type TransferrerPool = TVar (MkCheckTransferrer, [TransferrerPoolItem])
-
-type CheckTransferrer = IO Bool
-type MkCheckTransferrer = IO (IO Bool)
-
-{- Each item in the pool may have a transferrer running, and has an
- - IO action that can be used to check if it's still ok to use the
- - transferrer. -}
-data TransferrerPoolItem = TransferrerPoolItem (Maybe Transferrer) CheckTransferrer
-
-data Transferrer = Transferrer
-	{ transferrerRead :: Handle
-	, transferrerWrite :: Handle
-	, transferrerHandle :: ProcessHandle
-	}
-
-newTransferrerPool :: MkCheckTransferrer -> IO TransferrerPool
-newTransferrerPool c = newTVarIO (c, [])
-
-popTransferrerPool :: TransferrerPool -> STM (Maybe TransferrerPoolItem, Int)
-popTransferrerPool p = do
-	(c, l) <- readTVar p
-	case l of
-		[] -> return (Nothing, 0)
-		(i:is) -> do
-			writeTVar p (c, is)
-			return $ (Just i, length is)
-
-pushTransferrerPool :: TransferrerPool -> TransferrerPoolItem -> STM ()
-pushTransferrerPool p i = do
-	(c, l) <- readTVar p
-	let l' = i:l
-	writeTVar p (c, l')
-
-{- Note that making a CheckTransferrer may allocate resources,
- - such as a NotificationHandle, so it's important that the returned
- - TransferrerPoolItem is pushed into the pool, and not left to be
- - garbage collected. -}
-mkTransferrerPoolItem :: TransferrerPool -> Transferrer -> IO TransferrerPoolItem
-mkTransferrerPoolItem p t = do
-	mkcheck <- atomically $ fst <$> readTVar p
-	check <- mkcheck
-	return $ TransferrerPoolItem (Just t) check
+import Control.Concurrent.STM
 
 checkNetworkConnections :: DaemonStatusHandle -> MkCheckTransferrer
 checkNetworkConnections dstatushandle = do

Types/TransferrerPool.hs

@@ -0,0 +1,56 @@
+{- A pool of "git-annex transferkeys" processes available for use
+ -
+ - Copyright 2013-2020 Joey Hess <id@joeyh.name>
+ -
+ - Licensed under the GNU AGPL version 3 or higher.
+ -}
+
+module Types.TransferrerPool where
+
+import Annex.Common
+
+import Control.Concurrent.STM hiding (check)
+
+type TransferrerPool = TVar (MkCheckTransferrer, [TransferrerPoolItem])
+
+type CheckTransferrer = IO Bool
+type MkCheckTransferrer = IO (IO Bool)
+
+{- Each item in the pool may have a transferrer running, and has an
+ - IO action that can be used to check if it's still ok to use the
+ - transferrer. -}
+data TransferrerPoolItem = TransferrerPoolItem (Maybe Transferrer) CheckTransferrer
+
+data Transferrer = Transferrer
+	{ transferrerRead :: Handle
+	, transferrerWrite :: Handle
+	, transferrerHandle :: ProcessHandle
+	}
+
+newTransferrerPool :: MkCheckTransferrer -> IO TransferrerPool
+newTransferrerPool c = newTVarIO (c, [])
+
+popTransferrerPool :: TransferrerPool -> STM (Maybe TransferrerPoolItem, Int)
+popTransferrerPool p = do
+	(c, l) <- readTVar p
+	case l of
+		[] -> return (Nothing, 0)
+		(i:is) -> do
+			writeTVar p (c, is)
+			return $ (Just i, length is)
+
+pushTransferrerPool :: TransferrerPool -> TransferrerPoolItem -> STM ()
+pushTransferrerPool p i = do
+	(c, l) <- readTVar p
+	let l' = i:l
+	writeTVar p (c, l')
+
+{- Note that making a CheckTransferrer may allocate resources,
+ - such as a NotificationHandle, so it's important that the returned
+ - TransferrerPoolItem is pushed into the pool, and not left to be
+ - garbage collected. -}
+mkTransferrerPoolItem :: TransferrerPool -> Transferrer -> IO TransferrerPoolItem
+mkTransferrerPoolItem p t = do
+	mkcheck <- atomically $ fst <$> readTVar p
+	check <- mkcheck
+	return $ TransferrerPoolItem (Just t) check

Utility/Batch.hs

@@ -10,6 +10,7 @@
 module Utility.Batch (
 	batch,
 	BatchCommandMaker,
+	nonBatchCommandMaker,
 	getBatchCommandMaker,
 	toBatchCommand,
 	batchCommand,
@@ -50,6 +51,9 @@ batch a = a
  - are available in the path. -}
 type BatchCommandMaker = (String, [CommandParam]) -> (String, [CommandParam])
 
+nonBatchCommandMaker :: BatchCommandMaker
+nonBatchCommandMaker = id
+
 getBatchCommandMaker :: IO BatchCommandMaker
 getBatchCommandMaker = do
 #ifndef mingw32_HOST_OS

git-annex.cabal

@@ -479,7 +479,6 @@ Executable git-annex
       Assistant.Threads.Watcher
       Assistant.TransferQueue
       Assistant.TransferSlots
-      Assistant.TransferrerPool
       Assistant.Types.Alert
       Assistant.Types.BranchChange
       Assistant.Types.Changes
@@ -666,6 +665,7 @@ Executable git-annex
     Annex.TaggedPush
     Annex.Tmp
     Annex.Transfer
+    Annex.TransferrerPool
     Annex.UntrustedFilePath
     Annex.UpdateInstead
     Annex.UUID
@@ -1027,6 +1027,7 @@ Executable git-annex
     Types.StoreRetrieve
     Types.Test
     Types.Transfer
+    Types.TransferrerPool
     Types.TrustLevel
     Types.UUID
     Types.UrlContents