fs/accounting: add remote control of bwlimit

docs/content/docs.md

@@ -306,6 +306,11 @@ running, you can toggle the limiter like this:
 
     kill -SIGUSR2 $(pidof rclone)
 
+If you configure rclone with a [remote control](/rc) then you can use
+change the bwlimit dynamically:
+
+    rclone rc core/bwlimit rate=1M
+
 ### --buffer-size=SIZE ###
 
 Use this sized buffer to speed up file transfers.  Each `--transfer`

docs/content/rc.md

@@ -69,10 +69,20 @@ control commands.
 
 ## Supported commands
 
+### core/bwlimit: Set the bandwidth limit.
+
+This sets the bandwidth limit to that passed in.
+
+Eg
+
+    rclone core/bwlimit rate=1M
+    rclone core/bwlimit rate=off
+
 ### cache/expire: Purge a remote from cache
 
 Purge a remote from the cache backend. Supports either a directory or a file.
 Params:
+
   - remote = path to remote (required)
   - withData = true/false to delete cached data (chunks) as well (optional)
 

fs/accounting/token_bucket.go

@@ -5,6 +5,8 @@ import (
 	"time"
 
 	"github.com/ncw/rclone/fs"
+	"github.com/ncw/rclone/fs/rc"
+	"github.com/pkg/errors"
 	"golang.org/x/net/context" // switch to "context" when we stop supporting go1.6
 	"golang.org/x/time/rate"
 )
@@ -112,3 +114,46 @@ func limitBandwidth(n int) {
 
 	tokenBucketMu.Unlock()
 }
+
+// Remote control for the token bucket
+func init() {
+	rc.Add(rc.Call{
+		Path: "core/bwlimit",
+		Fn: func(in rc.Params) (out rc.Params, err error) {
+			ibwlimit, ok := in["rate"]
+			if !ok {
+				return out, errors.Errorf("parameter rate not found")
+			}
+			bwlimit, ok := ibwlimit.(string)
+			if !ok {
+				return out, errors.Errorf("value must be string rate=%v", ibwlimit)
+			}
+			var bws fs.BwTimetable
+			err = bws.Set(bwlimit)
+			if err != nil {
+				return out, errors.Wrap(err, "bad bwlimit")
+			}
+			if len(bws) != 1 {
+				return out, errors.New("need exactly 1 bandwidth setting")
+			}
+			bw := bws[0]
+			tokenBucketMu.Lock()
+			tokenBucket = newTokenBucket(bw.Bandwidth)
+			tokenBucketMu.Unlock()
+			fs.Logf(nil, "Bandwidth limit set to %v", bw.Bandwidth)
+			return rc.Params{"rate": bw.Bandwidth.String()}, nil
+		},
+		Title: "Set the bandwidth limit.",
+		Help: `
+This sets the bandwidth limit to that passed in.
+
+Eg
+
+    rclone core/bwlimit rate=1M
+    rclone core/bwlimit rate=off
+
+The format of the parameter is exactly the same as passed to --bwlimit
+except only one bandwidth may be specified.
+`,
+	})
+}