git-annex/Remote/Helper/Chunked.hs
Joey Hess cf07a2c412 webapp: Progess bar fixes for many types of special remotes.
There was confusion in different parts of the progress bar code about
whether an update contained the total number of bytes transferred, or the
number of bytes transferred since the last update. One way this bug
showed up was progress bars that seemed to stick at zero for a long time.
In order to fix it comprehensively, I add a new BytesProcessed data type,
that is explicitly a total quantity of bytes, not a delta.

Note that this doesn't necessarily fix every problem with progress bars.
Particularly, buffering can now cause progress bars to seem to run ahead
of transfers, reaching 100% when data is still being uploaded.
2013-03-28 17:04:37 -04:00

127 lines
4.3 KiB
Haskell

{- git-annex chunked remotes
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Remote.Helper.Chunked where
import Common.Annex
import Utility.DataUnits
import Types.Remote
import Utility.Metered
import qualified Data.Map as M
import qualified Data.ByteString.Lazy as L
import Data.Int
import qualified Control.Exception as E
type ChunkSize = Maybe Int64
{- Gets a remote's configured chunk size. -}
chunkSize :: RemoteConfig -> ChunkSize
chunkSize m =
case M.lookup "chunksize" m of
Nothing -> Nothing
Just v -> case readSize dataUnits v of
Nothing -> error "bad chunksize"
Just size
| size <= 0 -> error "bad chunksize"
| otherwise -> Just $ fromInteger size
{- This is an extension that's added to the usual file (or whatever)
- where the remote stores a key. -}
type ChunkExt = String
{- A record of the number of chunks used.
-
- While this can be guessed at based on the size of the key, encryption
- makes that larger. Also, using this helps deal with changes to chunksize
- over the life of a remote.
-}
chunkCount :: ChunkExt
chunkCount = ".chunkcount"
{- Parses the String from the chunkCount file, and returns the files that
- are used to store the chunks. -}
listChunks :: FilePath -> String -> [FilePath]
listChunks basedest chunkcount = take count $ map (basedest ++) chunkStream
where
count = fromMaybe 0 $ readish chunkcount
{- An infinite stream of extensions to use for chunks. -}
chunkStream :: [ChunkExt]
chunkStream = map (\n -> ".chunk" ++ show n) [1 :: Integer ..]
{- Given the base destination to use to store a value,
- generates a stream of temporary destinations (just one when not chunking)
- and passes it to an action, which should chunk and store the data,
- and return the destinations it stored to, or [] on error. Then
- calls the storer to write the chunk count (if chunking). Finally, the
- finalizer is called to rename the tmp into the dest
- (and do any other cleanup).
-}
storeChunks :: Key -> FilePath -> FilePath -> ChunkSize -> ([FilePath] -> IO [FilePath]) -> (FilePath -> String -> IO ()) -> (FilePath -> FilePath -> IO ()) -> IO Bool
storeChunks key tmp dest chunksize storer recorder finalizer = either onerr return
=<< (E.try go :: IO (Either E.SomeException Bool))
where
go = do
stored <- storer tmpdests
when (chunksize /= Nothing) $ do
let chunkcount = basef ++ chunkCount
recorder chunkcount (show $ length stored)
finalizer tmp dest
return (not $ null stored)
onerr e = do
print e
return False
basef = tmp ++ keyFile key
tmpdests
| chunksize == Nothing = [basef]
| otherwise = map (basef ++ ) chunkStream
{- Given a list of destinations to use, chunks the data according to the
- ChunkSize, and runs the storer action to store each chunk. Returns
- the destinations where data was stored, or [] on error.
-
- This buffers each chunk in memory.
- More optimal versions of this can be written, that rely
- on L.toChunks to split the lazy bytestring into chunks (typically
- smaller than the ChunkSize), and eg, write those chunks to a Handle.
- But this is the best that can be done with the storer interface that
- writes a whole L.ByteString at a time.
-}
storeChunked :: ChunkSize -> [FilePath] -> (FilePath -> L.ByteString -> IO ()) -> L.ByteString -> IO [FilePath]
storeChunked chunksize dests storer content = either onerr return
=<< (E.try (go chunksize dests) :: IO (Either E.SomeException [FilePath]))
where
go _ [] = return [] -- no dests!?
go Nothing (d:_) = do
storer d content
return [d]
go (Just sz) _
-- always write a chunk, even if the data is 0 bytes
| L.null content = go Nothing dests
| otherwise = storechunks sz [] dests content
onerr e = do
print e
return []
storechunks _ _ [] _ = return [] -- ran out of dests
storechunks sz useddests (d:ds) b
| L.null b = return $ reverse useddests
| otherwise = do
let (chunk, b') = L.splitAt sz b
storer d chunk
storechunks sz (d:useddests) ds b'
{- Writes a series of chunks to a file. The feeder is called to get
- each chunk. -}
meteredWriteFileChunks :: MeterUpdate -> FilePath -> [v] -> (v -> IO L.ByteString) -> IO ()
meteredWriteFileChunks meterupdate dest chunks feeder =
withBinaryFile dest WriteMode $ \h ->
forM_ chunks $ \c ->
meteredWrite meterupdate h =<< feeder c