remove stale live changes from reposize database

Reorganized the reposize database directory, and split up a column.

checkStaleSizeChanges needs to run before needLiveUpdate,
otherwise the process won't be holding a lock on its pid file, and
another process could go in and expire the live update it records. It
just so happens that they do get called in the correct order, since
checking balanced preferred content calls getLiveRepoSizes before
needLiveUpdate.

The 1 minute delay between checks is arbitrary, but will avoid excess
work. The downside of it is that, if a process is dropping a file and
gets interrupted, for 1 minute another process can expect a repository
will soon be smaller than it is. And so a process might send data to a
repository when a file is not really going to be dropped from it. But
note that can already happen if a drop takes some time in eg locking and
then fails. So it seems possible that live updates should only be
allowed to increase, rather than decrease the size of a repository.

Types/RepoSize.hs

@@ -14,11 +14,11 @@ import Types.Key
 
 import Control.Concurrent
 import Database.Persist.Sql hiding (Key)
-import qualified Data.Text as T
 import Data.Unique
 import Text.Read
 import System.Process (Pid)
-import Utility.Split
+import qualified Data.Text as T
+import qualified Data.Set as S
 
 -- The current size of a repo.
 newtype RepoSize = RepoSize { fromRepoSize :: Integer }
@@ -62,36 +62,57 @@ instance PersistFieldSql SizeChange where
         sqlType _ = SqlInt32
 
 data SizeChangeId = SizeChangeId
-	{ sizeChangeUniqueId :: Int
-	-- ^ unique per process
-	, sizeChangeProcessId :: Integer
-	-- ^ a pid, using Integer for portability
+	{ sizeChangeUniqueId :: SizeChangeUniqueId
+	, sizeChangeProcessId :: SizeChangeProcessId
 	}
-	deriving (Show, Eq)
+	deriving (Show, Eq, Ord)
+
+-- A unique value for the current process.
+newtype SizeChangeUniqueId = SizeChangeUniqueId Int
+	deriving (Show, Eq, Ord)
+
+-- A pid, using Integer for portability
+newtype SizeChangeProcessId = SizeChangeProcessId Integer
+	deriving (Show, Eq, Ord)
 
 mkSizeChangeId :: Pid -> IO SizeChangeId
 mkSizeChangeId pid = do
 	u <- newUnique
 	return $ SizeChangeId
-		{ sizeChangeProcessId = fromIntegral pid
-		, sizeChangeUniqueId = hashUnique u
+		{ sizeChangeUniqueId = 
+			SizeChangeUniqueId $ hashUnique u
+		, sizeChangeProcessId = 
+			SizeChangeProcessId $ fromIntegral pid
 		}
 
-instance PersistField SizeChangeId where
-        toPersistValue cid = toPersistValue $ 
-		show (sizeChangeProcessId cid) ++ ":" ++ 
-		show (sizeChangeUniqueId cid)
+instance PersistField SizeChangeUniqueId where
+        toPersistValue (SizeChangeUniqueId i) = toPersistValue (show i)
 	fromPersistValue b = fromPersistValue b >>= parse
 	  where
 		parse s = maybe
-			(Left $ T.pack $ "bad serialized SizeChangeId " ++ show s)
+			(Left $ T.pack $ "bad serialized SizeChangeUniqueId " ++ show s)
 			Right
-			(parse' s)
-		parse' s = case splitc ':' s of
-			(pid:uid:[]) -> SizeChangeId
-				<$> readMaybe pid
-				<*> readMaybe uid
-			_ -> Nothing
+			(SizeChangeUniqueId <$> readMaybe s)
 
-instance PersistFieldSql SizeChangeId where
+instance PersistFieldSql SizeChangeUniqueId where
         sqlType _ = SqlString
+
+instance PersistField SizeChangeProcessId where
+        toPersistValue (SizeChangeProcessId i) = toPersistValue (show i)
+	fromPersistValue b = fromPersistValue b >>= parse
+	  where
+		parse s = maybe
+			(Left $ T.pack $ "bad serialized SizeChangeProcessId " ++ show s)
+			Right
+			(SizeChangeProcessId <$> readMaybe s)
+
+instance PersistFieldSql SizeChangeProcessId where
+        sqlType _ = SqlString
+
+newtype StaleSizeChanger = StaleSizeChanger
+	{ staleSizeChangerProcessId :: SizeChangeProcessId }
+	deriving (Show, Eq, Ord)
+
+isStaleSizeChangeId :: S.Set StaleSizeChanger -> SizeChangeId -> Bool
+isStaleSizeChangeId s cid =
+	StaleSizeChanger (sizeChangeProcessId cid) `S.member` s