git-annex/Annex/CatFile.hs
Joey Hess 34530e59d9
Avoid using a lot of memory when large objects are present in the git repository
.. and have to be checked to see if they are a pointed to an annexed file.

Cases where such memory use could occur included, but were not limited to:
  - git commit -a of a large unlocked file (in v5 mode)
  - git-annex adjust when a large file was checked into git directly
Generally, any use of catKey was a potential problem.

Fix by using git cat-file --batch-check to check size before catting.
This adds another git batch process, which is included in the CatFileHandle
for simplicity.

There could be performance impact, anywhere catKey is used. Particularly
likely to affect adjusted branch generation speed, and operations on
unlocked files in v6 mode. Hopefully since the --batch-check and
--batch read the same data, disk buffering will avoid most overhead.
Leaving only the overhead of talking to the process over the pipe and
whatever computation --batch-check needs to do.

This commit was sponsored by Bruno BEAUFILS on Patreon.
2016-10-05 15:24:13 -04:00

142 lines
4.5 KiB
Haskell

{- git cat-file interface, with handle automatically stored in the Annex monad
-
- Copyright 2011-2015 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Annex.CatFile (
catFile,
catFileDetails,
catObject,
catTree,
catCommit,
catObjectDetails,
catFileHandle,
catFileStop,
catKey,
catKeyFile,
catKeyFileHEAD,
catSymLinkTarget,
) where
import qualified Data.ByteString.Lazy as L
import qualified Data.Map as M
import System.PosixCompat.Types
import Annex.Common
import qualified Git
import qualified Git.CatFile
import qualified Annex
import Git.Types
import Git.FilePath
import Git.Index
import qualified Git.Ref
import Annex.Link
catFile :: Git.Branch -> FilePath -> Annex L.ByteString
catFile branch file = do
h <- catFileHandle
liftIO $ Git.CatFile.catFile h branch file
catFileDetails :: Git.Branch -> FilePath -> Annex (Maybe (L.ByteString, Sha, ObjectType))
catFileDetails branch file = do
h <- catFileHandle
liftIO $ Git.CatFile.catFileDetails h branch file
catObject :: Git.Ref -> Annex L.ByteString
catObject ref = do
h <- catFileHandle
liftIO $ Git.CatFile.catObject h ref
catObjectMetaData :: Git.Ref -> Annex (Maybe (Integer, ObjectType))
catObjectMetaData ref = do
h <- catFileHandle
liftIO $ Git.CatFile.catObjectMetaData h ref
catTree :: Git.Ref -> Annex [(FilePath, FileMode)]
catTree ref = do
h <- catFileHandle
liftIO $ Git.CatFile.catTree h ref
catCommit :: Git.Ref -> Annex (Maybe Commit)
catCommit ref = do
h <- catFileHandle
liftIO $ Git.CatFile.catCommit h ref
catObjectDetails :: Git.Ref -> Annex (Maybe (L.ByteString, Sha, ObjectType))
catObjectDetails ref = do
h <- catFileHandle
liftIO $ Git.CatFile.catObjectDetails h ref
{- There can be multiple index files, and a different cat-file is needed
- for each. This is selected by setting GIT_INDEX_FILE in the gitEnv. -}
catFileHandle :: Annex Git.CatFile.CatFileHandle
catFileHandle = do
m <- Annex.getState Annex.catfilehandles
indexfile <- fromMaybe "" . maybe Nothing (lookup indexEnv)
<$> fromRepo gitEnv
case M.lookup indexfile m of
Just h -> return h
Nothing -> do
h <- inRepo Git.CatFile.catFileStart
let m' = M.insert indexfile h m
Annex.changeState $ \s -> s { Annex.catfilehandles = m' }
return h
{- Stops all running cat-files. Should only be run when it's known that
- nothing is using the handles, eg at shutdown. -}
catFileStop :: Annex ()
catFileStop = do
m <- Annex.withState $ pure . \s ->
(s { Annex.catfilehandles = M.empty }, Annex.catfilehandles s)
liftIO $ mapM_ Git.CatFile.catFileStop (M.elems m)
{- From ref to a symlink or a pointer file, get the key. -}
catKey :: Ref -> Annex (Maybe Key)
catKey ref = go =<< catObjectMetaData ref
where
go (Just (sz, _))
-- Avoid catting large files, that cannot be symlinks or
-- pointer files, which would require buffering their
-- content in memory, as well as a lot of IO.
| sz <= maxPointerSz = parseLinkOrPointer <$> catObject ref
go _ = return Nothing
{- Gets a symlink target. -}
catSymLinkTarget :: Sha -> Annex String
catSymLinkTarget sha = fromInternalGitPath . decodeBS <$> get
where
-- Avoid buffering the whole file content, which might be large.
-- 8192 is enough if it really is a symlink.
get = L.take 8192 <$> catObject sha
{- From a file in the repository back to the key.
-
- Ideally, this should reflect the key that's staged in the index,
- not the key that's committed to HEAD. Unfortunately, git cat-file
- does not refresh the index file after it's started up, so things
- newly staged in the index won't show up. It does, however, notice
- when branches change.
-
- For command-line git-annex use, that doesn't matter. It's perfectly
- reasonable for things staged in the index after the currently running
- git-annex process to not be noticed by it. However, we do want to see
- what's in the index, since it may have uncommitted changes not in HEAD
-
- For the assistant, this is much more of a problem, since it commits
- files and then needs to be able to immediately look up their keys.
- OTOH, the assistant doesn't keep changes staged in the index for very
- long at all before committing them -- and it won't look at the keys
- of files until after committing them.
-
- So, this gets info from the index, unless running as a daemon.
-}
catKeyFile :: FilePath -> Annex (Maybe Key)
catKeyFile f = ifM (Annex.getState Annex.daemon)
( catKeyFileHEAD f
, catKey $ Git.Ref.fileRef f
)
catKeyFileHEAD :: FilePath -> Annex (Maybe Key)
catKeyFileHEAD f = catKey $ Git.Ref.fileFromRef Git.Ref.headRef f