WIP multipart S3 upload

I'm a little stuck on getting the list of etags of the parts.
This seems to require taking the md5 of each part locally,
which doesn't get along well with lazily streaming in the part from the
file. It would need to read the file twice, or lose laziness and buffer a
whole part -- but parts might be quite large.

This seems to be a problem with the API provided; S3 is supposed to return
an etag, but that is not exposed. I have filed a bug:
https://github.com/aristidb/aws/issues/141

Remote/S3.hs

@@ -40,6 +40,7 @@ import Creds
 import Annex.UUID
 import Logs.Web
 import Utility.Metered
+import Utility.DataUnits
 
 type BucketName = String
 
@@ -151,14 +152,46 @@ prepareS3 r info = resourcePrepare $ const $
 
 store :: Remote -> S3Handle -> Storer
 store r h = fileStorer $ \k f p -> do
-	rbody <- liftIO $ httpBodyStorer f p
-	void $ sendS3Handle h $ putObject h (bucketObject (hinfo h) k) rbody
-	
+	case partSize (hinfo h) of
+		Just sz -> do
+			fsz <- fromIntegral . fileSize <$> liftIO (getFileStatus f)
+			if fsz > sz
+				then multipartupload sz k f p
+				else singlepartupload k f p
+		Nothing -> singlepartupload k f p	
 	-- Store public URL to item in Internet Archive.
 	when (isIA (hinfo h) && not (isChunkKey k)) $
 		setUrlPresent k (iaKeyUrl r k)
-	
 	return True
+  where
+	singlepartupload k f p = do
+		rbody <- liftIO $ httpBodyStorer f p
+		void $ sendS3Handle h $ putObject h (bucketObject (hinfo h) k) rbody
+	multipartupload sz k f p = do
+#if MIN_VERSION_aws(0,10,4)
+		let info = hinfo h
+		let objects = bucketObject info h
+
+		uploadid <- S3.imurUploadId <$> sendS3Handle' h $ 
+			(S3.postInitiateMultipartUpload (bucket info) object)
+				{ S3.imuStorageClass = Just (storageClass info)
+				, S3.imuMetadata = metaHeaders info
+				, S3.imuAutoMakeBucket = isIA info
+				, S3.imuExpires = Nothing -- TODO set some reasonable expiry
+				}
+
+		-- TODO open file, read each part of size sz (streaming
+		-- it); send part to S3, and get a list of etags of all
+		-- the parts
+		
+
+		void $ sendS3Handle' h $
+			S3.postCompleteMultipartUpload (bucket info) object uploadid $
+				zip [1..] (map T.pack etags)
+#else
+		warning $ "Cannot do multipart upload (partsize " ++ show sz ++ "); built with too old a version of the aws library."
+		singlepartupload k f p
+#endif
 
 {- Implemented as a fileRetriever, that uses conduit to stream the chunks
  - out to the file. Would be better to implement a byteRetriever, but
@@ -373,6 +406,7 @@ data S3Info = S3Info
 	, storageClass :: S3.StorageClass
 	, bucketObject :: Key -> T.Text
 	, metaHeaders :: [(T.Text, T.Text)]
+	, partSize :: Maybe Integer
 	, isIA :: Bool
 	}
 
@@ -387,6 +421,7 @@ extractS3Info c = do
 		, storageClass = getStorageClass c
 		, bucketObject = T.pack . getBucketObject c
 		, metaHeaders = getMetaHeaders c
+		, partSize = getPartSize c
 		, isIA = configIA c
 		}
 
@@ -397,7 +432,10 @@ getStorageClass :: RemoteConfig -> S3.StorageClass
 getStorageClass c = case M.lookup "storageclass" c of
 	Just "REDUCED_REDUNDANCY" -> S3.ReducedRedundancy
 	_ -> S3.Standard
-	
+
+getPartSize :: RemoteConfig -> Maybe Integer
+getPartSize c = readSize dataUnits =<< M.lookup "partsize" c
+
 getMetaHeaders :: RemoteConfig -> [(T.Text, T.Text)]
 getMetaHeaders = map munge . filter ismetaheader . M.assocs
   where

doc/special_remotes/S3.mdwn

@@ -21,6 +21,11 @@ the S3 remote.
 * `chunk` - Enables [[chunking]] when storing large files.
   `chunk=1MiB` is a good starting point for chunking.
 
+* `partsize` - Specifies the largest object to attempt to store in the
+  bucket. Multipart uploads will be used when storing larger objects.
+  This is not enabled by default, but can be enabled or changed at any
+  time. Setting `partsize=1GiB` is reasonable for S3.
+
 * `keyid` - Specifies the gpg key to use for [[encryption]].
 
 * `embedcreds` - Optional. Set to "yes" embed the login credentials inside

git-annex.cabal

@@ -159,7 +159,7 @@ Executable git-annex
     if flag(PatchedAWS)
       Build-Depends: aws (>= 0.9.2)
     else
-      Build-Depends: aws (>= 0.10.2)
+      Build-Depends: aws (>= 0.10.4)
     CPP-Options: -DWITH_S3
 
   if flag(WebDAV)