acd: Download files >= 9GB with their tempLink direct from s3

This files the problem downloading files > 10GB.

Fixes #204 Fixes #313

amazonclouddrive/amazonclouddrive.go

@@ -27,6 +27,7 @@ import (
 	"github.com/ncw/rclone/fs"
 	"github.com/ncw/rclone/oauthutil"
 	"github.com/ncw/rclone/pacer"
+	"github.com/spf13/pflag"
 	"golang.org/x/oauth2"
 )
 
@@ -44,6 +45,8 @@ const (
 
 // Globals
 var (
+	// Flags
+	tempLinkThreshold = fs.SizeSuffix(9 << 30) // Download files bigger than this via the tempLink
 	// Description of how to auth for this app
 	acdConfig = &oauth2.Config{
 		Scopes: []string{"clouddrive:read_all", "clouddrive:write"},
@@ -76,12 +79,14 @@ func init() {
 			Help: "Amazon Application Client Secret - leave blank normally.",
 		}},
 	})
+	pflag.VarP(&tempLinkThreshold, "acd-templink-threshold", "", "Files >= this size will be downloaded via their tempLink.")
 }
 
 // Fs represents a remote acd server
 type Fs struct {
 	name         string             // name of this remote
 	c            *acd.Client        // the connection to the acd server
+	noAuthClient *http.Client       // unauthenticated http client
 	root         string             // the path we are working on
 	dirCache     *dircache.DirCache // Map of directory path to directory id
 	pacer        *pacer.Pacer       // pacer for API calls
@@ -150,6 +155,7 @@ func NewFs(name, root string) (fs.Fs, error) {
 		root:         root,
 		c:            c,
 		pacer:        pacer.New().SetMinSleep(minSleep).SetPacer(pacer.AmazonCloudDrivePacer),
+		noAuthClient: fs.Config.Client(),
 	}
 
 	// Update endpoints
@@ -741,10 +747,18 @@ func (o *Object) Storable() bool {
 
 // Open an object for read
 func (o *Object) Open() (in io.ReadCloser, err error) {
+	bigObject := o.Size() >= int64(tempLinkThreshold)
+	if bigObject {
+		fs.Debug(o, "Dowloading large object via tempLink")
+	}
 	file := acd.File{Node: o.info}
 	var resp *http.Response
 	err = o.fs.pacer.Call(func() (bool, error) {
+		if !bigObject {
 			in, resp, err = file.Open()
+		} else {
+			in, resp, err = file.OpenTempURL(o.fs.noAuthClient)
+		}
 		return shouldRetry(resp, err)
 	})
 	return in, err

docs/content/amazonclouddrive.md

@@ -96,6 +96,22 @@ don't provide an API to permanently delete files, nor to empty the
 trash, so you will have to do that with one of Amazon's apps or via
 the Amazon cloud drive website.
 
+### Specific options ###
+
+Here are the command line options specific to this cloud storage
+system.
+
+#### --acd-templink-threshold=SIZE ####
+
+Files this size or more will be downloaded via their `tempLink`. This
+is to work around a problem with Amazon Cloud Drive which blocks
+downloads of files bigger than about 10GB.  The default for this is
+9GB which shouldn't need to be changed.
+
+To download files above this threshold, rclone requests a `tempLink`
+which downloads the file through a temporary URL directly from the
+underlying S3 storage.
+
 ### Limitations ###
 
 Note that Amazon cloud drive is case insensitive so you can't have a