From 0caad1e890bd016cfac2e76a39c0de1840520579 Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Sat, 7 Nov 2020 01:41:22 +0100
Subject: [PATCH] copy: parallelize tree walk

---
 cmd/restic/cmd_copy.go | 107 +++++++++++++++++++++--------------------
 1 file changed, 55 insertions(+), 52 deletions(-)

diff --git a/cmd/restic/cmd_copy.go b/cmd/restic/cmd_copy.go
index 216dab836..37cf45ec3 100644
--- a/cmd/restic/cmd_copy.go
+++ b/cmd/restic/cmd_copy.go
@@ -6,6 +6,7 @@ import (
 
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/restic"
+	"golang.org/x/sync/errgroup"
 
 	"github.com/spf13/cobra"
 )
@@ -184,57 +185,59 @@ type treeCloner struct {
 	buf          []byte
 }
 
-func (t *treeCloner) copyTree(ctx context.Context, treeID restic.ID) error {
-	// We have already processed this tree
-	if t.visitedTrees.Has(treeID) {
+func (t *treeCloner) copyTree(ctx context.Context, rootTreeID restic.ID) error {
+	wg, ctx := errgroup.WithContext(ctx)
+
+	treeStream := restic.StreamTrees(ctx, wg, t.srcRepo, restic.IDs{rootTreeID}, func(treeID restic.ID) bool {
+		visited := t.visitedTrees.Has(treeID)
+		t.visitedTrees.Insert(treeID)
+		return visited
+	})
+
+	wg.Go(func() error {
+		for tree := range treeStream {
+			if tree.Error != nil {
+				return fmt.Errorf("LoadTree(%v) returned error %v", tree.ID.Str(), tree.Error)
+			}
+
+			// Do we already have this tree blob?
+			if !t.dstRepo.Index().Has(restic.BlobHandle{ID: tree.ID, Type: restic.TreeBlob}) {
+				newTreeID, err := t.dstRepo.SaveTree(ctx, tree.Tree)
+				if err != nil {
+					return fmt.Errorf("SaveTree(%v) returned error %v", tree.ID.Str(), err)
+				}
+				// Assurance only.
+				if newTreeID != tree.ID {
+					return fmt.Errorf("SaveTree(%v) returned unexpected id %s", tree.ID.Str(), newTreeID.Str())
+				}
+			}
+
+			// TODO: parallelize blob down/upload
+
+			for _, entry := range tree.Nodes {
+				// Recursion into directories is handled by StreamTrees
+				// Copy the blobs for this file.
+				for _, blobID := range entry.Content {
+					// Do we already have this data blob?
+					if t.dstRepo.Index().Has(restic.BlobHandle{ID: blobID, Type: restic.DataBlob}) {
+						continue
+					}
+					debug.Log("Copying blob %s\n", blobID.Str())
+					var err error
+					t.buf, err = t.srcRepo.LoadBlob(ctx, restic.DataBlob, blobID, t.buf)
+					if err != nil {
+						return fmt.Errorf("LoadBlob(%v) returned error %v", blobID, err)
+					}
+
+					_, _, err = t.dstRepo.SaveBlob(ctx, restic.DataBlob, t.buf, blobID, false)
+					if err != nil {
+						return fmt.Errorf("SaveBlob(%v) returned error %v", blobID, err)
+					}
+				}
+			}
+
+		}
 		return nil
-	}
-
-	tree, err := t.srcRepo.LoadTree(ctx, treeID)
-	if err != nil {
-		return fmt.Errorf("LoadTree(%v) returned error %v", treeID.Str(), err)
-	}
-	t.visitedTrees.Insert(treeID)
-
-	// Do we already have this tree blob?
-	if !t.dstRepo.Index().Has(restic.BlobHandle{ID: treeID, Type: restic.TreeBlob}) {
-		newTreeID, err := t.dstRepo.SaveTree(ctx, tree)
-		if err != nil {
-			return fmt.Errorf("SaveTree(%v) returned error %v", treeID.Str(), err)
-		}
-		// Assurance only.
-		if newTreeID != treeID {
-			return fmt.Errorf("SaveTree(%v) returned unexpected id %s", treeID.Str(), newTreeID.Str())
-		}
-	}
-
-	// TODO: parellize this stuff, likely only needed inside a tree.
-
-	for _, entry := range tree.Nodes {
-		// If it is a directory, recurse
-		if entry.Type == "dir" && entry.Subtree != nil {
-			if err := t.copyTree(ctx, *entry.Subtree); err != nil {
-				return err
-			}
-		}
-		// Copy the blobs for this file.
-		for _, blobID := range entry.Content {
-			// Do we already have this data blob?
-			if t.dstRepo.Index().Has(restic.BlobHandle{ID: blobID, Type: restic.DataBlob}) {
-				continue
-			}
-			debug.Log("Copying blob %s\n", blobID.Str())
-			t.buf, err = t.srcRepo.LoadBlob(ctx, restic.DataBlob, blobID, t.buf)
-			if err != nil {
-				return fmt.Errorf("LoadBlob(%v) returned error %v", blobID, err)
-			}
-
-			_, _, err = t.dstRepo.SaveBlob(ctx, restic.DataBlob, t.buf, blobID, false)
-			if err != nil {
-				return fmt.Errorf("SaveBlob(%v) returned error %v", blobID, err)
-			}
-		}
-	}
-
-	return nil
+	})
+	return wg.Wait()
 }