git-annex/GitQueue.hs
Joey Hess bc21502b9a use queue when upgrading, flushing every so often
Added a cheap way to query the size of a queue.

runQueueAt is not the default yet only because there may be some code that
expects to be able to queue some suff, do something else, and run the whole
queue at the end.

10240 is an arbitrary size for the queue. If we assume annexed
filenames are between 10 and 255 characters long, then the queue will
build up between 100kb and 2550kb long commands. The max command line
length on linux is somewhere above 20k, so this is a fairly good balance --
the queue will buffer only a few megabytes of stuff and a minimal number
of commands will be run by xargs.

Also, insert queue items strictly, this should save memory.
2011-03-16 15:10:15 -04:00

69 lines
1.8 KiB
Haskell

{- git repository command queue
-
- Copyright 2010 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module GitQueue (
Queue,
empty,
add,
size,
run
) where
import qualified Data.Map as M
import System.IO
import System.Cmd.Utils
import Data.String.Utils
import Control.Monad (unless, forM_)
import Utility
import qualified GitRepo as Git
{- An action to perform in a git repository. The file to act on
- is not included, and must be able to be appended after the params. -}
data Action = Action {
getSubcommand :: String,
getParams :: [CommandParam]
} deriving (Show, Eq, Ord)
{- A queue of actions to perform (in any order) on a git repository,
- with lists of files to perform them on. This allows coalescing
- similar git commands. -}
data Queue = Queue Integer (M.Map Action [FilePath])
deriving (Show, Eq)
{- Constructor for empty queue. -}
empty :: Queue
empty = Queue 0 M.empty
{- Adds an action to a queue. -}
add :: Queue -> String -> [CommandParam] -> FilePath -> Queue
add (Queue n m) subcommand params file = Queue (n + 1) m'
where
action = Action subcommand params
m' = M.insertWith' (++) action [file] m
{- Number of items in a queue. -}
size :: Queue -> Integer
size (Queue n _) = n
{- Runs a queue on a git repository. -}
run :: Git.Repo -> Queue -> IO ()
run repo (Queue _ m) = do
forM_ (M.toList m) $ uncurry $ runAction repo
return ()
{- Runs an Action on a list of files in a git repository.
-
- Complicated by commandline length limits. -}
runAction :: Git.Repo -> Action -> [FilePath] -> IO ()
runAction repo action files = do
unless (null files) runxargs
where
runxargs = pOpen WriteToPipe "xargs" ("-0":"git":params) feedxargs
params = toCommand $ Git.gitCommandLine repo
(Param (getSubcommand action):getParams action)
feedxargs h = hPutStr h $ join "\0" files