chunker: partially implement no-rename transactions (#4675)

Some storage providers e.g. S3 don't have an efficient rename operation.
Before this change, when chunker finished an upload, the server-side copy
and delete operations that renamed temporary chunks to their final names
could take a significant amount of time.
This PR records transaction identifier (versioning) in the metadata of
chunker composite objects striving to remove the need for rename
operations on such backends.
This approach will be triggered be the new "transactions" configuration
option, which can be "rename" (the default) or "norename".
We implement the new approach for uploads (Put operations).
The chunker Move operation still uses the rename operation of
underlying backend. Filling this gap is left for a later PR.

Co-authored-by: Ivan Andreev <ivandeex@gmail.com>

backend/chunker/chunker_internal_test.go

@@ -468,9 +468,15 @@ func testPreventCorruption(t *testing.T, f *Fs) {
 		return obj
 	}
 	billyObj := newFile("billy")
+	billyTxn := billyObj.(*Object).xactID
+	if f.useNoRename {
+		require.True(t, billyTxn != "")
+	} else {
+		require.True(t, billyTxn == "")
+	}
 
 	billyChunkName := func(chunkNo int) string {
-		return f.makeChunkName(billyObj.Remote(), chunkNo, "", "")
+		return f.makeChunkName(billyObj.Remote(), chunkNo, "", billyTxn)
 	}
 
 	err := f.Mkdir(ctx, billyChunkName(1))
@@ -487,6 +493,8 @@ func testPreventCorruption(t *testing.T, f *Fs) {
 	// accessing chunks in strict mode is prohibited
 	f.opt.FailHard = true
 	billyChunk4Name := billyChunkName(4)
+	_, err = f.base.NewObject(ctx, billyChunk4Name)
+	require.NoError(t, err)
 	billyChunk4, err := f.NewObject(ctx, billyChunk4Name)
 	assertOverlapError(err)
 
@@ -520,7 +528,8 @@ func testPreventCorruption(t *testing.T, f *Fs) {
 
 	// recreate billy in case it was anyhow corrupted
 	willyObj := newFile("willy")
-	willyChunkName := f.makeChunkName(willyObj.Remote(), 1, "", "")
+	willyTxn := willyObj.(*Object).xactID
+	willyChunkName := f.makeChunkName(willyObj.Remote(), 1, "", willyTxn)
 	f.opt.FailHard = false
 	willyChunk, err := f.NewObject(ctx, willyChunkName)
 	f.opt.FailHard = true
@@ -561,17 +570,20 @@ func testChunkNumberOverflow(t *testing.T, f *Fs) {
 	modTime := fstest.Time("2001-02-03T04:05:06.499999999Z")
 	contents := random.String(100)
 
-	newFile := func(f fs.Fs, name string) (fs.Object, string) {
-		filename := path.Join(dir, name)
+	newFile := func(f fs.Fs, name string) (obj fs.Object, filename string, txnID string) {
+		filename = path.Join(dir, name)
 		item := fstest.Item{Path: filename, ModTime: modTime}
-		_, obj := fstests.PutTestContents(ctx, t, f, &item, contents, true)
+		_, obj = fstests.PutTestContents(ctx, t, f, &item, contents, true)
 		require.NotNil(t, obj)
-		return obj, filename
+		if chunkObj, isChunkObj := obj.(*Object); isChunkObj {
+			txnID = chunkObj.xactID
+		}
+		return
 	}
 
 	f.opt.FailHard = false
-	file, fileName := newFile(f, "wreaker")
-	wreak, _ := newFile(f.base, f.makeChunkName("wreaker", wreakNumber, "", ""))
+	file, fileName, fileTxn := newFile(f, "wreaker")
+	wreak, _, _ := newFile(f.base, f.makeChunkName("wreaker", wreakNumber, "", fileTxn))
 
 	f.opt.FailHard = false
 	fstest.CheckListingWithRoot(t, f, dir, nil, nil, f.Precision())
@@ -650,7 +662,7 @@ func testMetadataInput(t *testing.T, f *Fs) {
 		}
 	}
 
-	metaData, err := marshalSimpleJSON(ctx, 3, 1, "", "")
+	metaData, err := marshalSimpleJSON(ctx, 3, 1, "", "", "")
 	require.NoError(t, err)
 	todaysMeta := string(metaData)
 	runSubtest(todaysMeta, "today")
@@ -664,7 +676,7 @@ func testMetadataInput(t *testing.T, f *Fs) {
 	runSubtest(futureMeta, "future")
 }
 
-// test that chunker refuses to change on objects with future/unknowm metadata
+// Test that chunker refuses to change on objects with future/unknown metadata
 func testFutureProof(t *testing.T, f *Fs) {
 	if f.opt.MetaFormat == "none" {
 		t.Skip("this test requires metadata support")
@@ -738,6 +750,100 @@ func testFutureProof(t *testing.T, f *Fs) {
 	}
 }
 
+// The newer method of doing transactions without renaming should still be able to correctly process chunks that were created with renaming
+// If you attempt to do the inverse, however, the data chunks will be ignored causing commands to perform incorrectly
+func testBackwardsCompatibility(t *testing.T, f *Fs) {
+	if !f.useMeta {
+		t.Skip("Can't do norename transactions without metadata")
+	}
+	const dir = "backcomp"
+	ctx := context.Background()
+	saveOpt := f.opt
+	saveUseNoRename := f.useNoRename
+	defer func() {
+		f.opt.FailHard = false
+		_ = operations.Purge(ctx, f.base, dir)
+		f.opt = saveOpt
+		f.useNoRename = saveUseNoRename
+	}()
+	f.opt.ChunkSize = fs.SizeSuffix(10)
+
+	modTime := fstest.Time("2001-02-03T04:05:06.499999999Z")
+	contents := random.String(250)
+	newFile := func(f fs.Fs, name string) (fs.Object, string) {
+		filename := path.Join(dir, name)
+		item := fstest.Item{Path: filename, ModTime: modTime}
+		_, obj := fstests.PutTestContents(ctx, t, f, &item, contents, true)
+		require.NotNil(t, obj)
+		return obj, filename
+	}
+
+	f.opt.FailHard = false
+	f.useNoRename = false
+	file, fileName := newFile(f, "renamefile")
+
+	f.opt.FailHard = false
+	item := fstest.NewItem(fileName, contents, modTime)
+
+	var items []fstest.Item
+	items = append(items, item)
+
+	f.useNoRename = true
+	fstest.CheckListingWithRoot(t, f, dir, items, nil, f.Precision())
+	_, err := f.NewObject(ctx, fileName)
+	assert.NoError(t, err)
+
+	f.opt.FailHard = true
+	_, err = f.List(ctx, dir)
+	assert.NoError(t, err)
+
+	f.opt.FailHard = false
+	_ = file.Remove(ctx)
+}
+
+func testChunkerServerSideMove(t *testing.T, f *Fs) {
+	if !f.useMeta {
+		t.Skip("Can't test norename transactions without metadata")
+	}
+
+	ctx := context.Background()
+	const dir = "servermovetest"
+	subRemote := fmt.Sprintf("%s:%s/%s", f.Name(), f.Root(), dir)
+
+	subFs1, err := fs.NewFs(ctx, subRemote+"/subdir1")
+	assert.NoError(t, err)
+	fs1, isChunkerFs := subFs1.(*Fs)
+	assert.True(t, isChunkerFs)
+	fs1.useNoRename = false
+	fs1.opt.ChunkSize = fs.SizeSuffix(3)
+
+	subFs2, err := fs.NewFs(ctx, subRemote+"/subdir2")
+	assert.NoError(t, err)
+	fs2, isChunkerFs := subFs2.(*Fs)
+	assert.True(t, isChunkerFs)
+	fs2.useNoRename = true
+	fs2.opt.ChunkSize = fs.SizeSuffix(3)
+
+	modTime := fstest.Time("2001-02-03T04:05:06.499999999Z")
+	item := fstest.Item{Path: "movefile", ModTime: modTime}
+	contents := "abcdef"
+	_, file := fstests.PutTestContents(ctx, t, fs1, &item, contents, true)
+
+	dstOverwritten, _ := fs2.NewObject(ctx, "movefile")
+	dstFile, err := operations.Move(ctx, fs2, dstOverwritten, "movefile", file)
+	assert.NoError(t, err)
+	assert.Equal(t, int64(len(contents)), dstFile.Size())
+
+	r, err := dstFile.Open(ctx)
+	assert.NoError(t, err)
+	assert.NotNil(t, r)
+	data, err := ioutil.ReadAll(r)
+	assert.NoError(t, err)
+	assert.Equal(t, contents, string(data))
+	_ = r.Close()
+	_ = operations.Purge(ctx, f.base, dir)
+}
+
 // InternalTest dispatches all internal tests
 func (f *Fs) InternalTest(t *testing.T) {
 	t.Run("PutLarge", func(t *testing.T) {
@@ -764,6 +870,12 @@ func (f *Fs) InternalTest(t *testing.T) {
 	t.Run("FutureProof", func(t *testing.T) {
 		testFutureProof(t, f)
 	})
+	t.Run("BackwardsCompatibility", func(t *testing.T) {
+		testBackwardsCompatibility(t, f)
+	})
+	t.Run("ChunkerServerSideMove", func(t *testing.T) {
+		testChunkerServerSideMove(t, f)
+	})
 }
 
 var _ fstests.InternalTester = (*Fs)(nil)