always write index data for VDR, never check on duplicate

vdr/didstore/event.go

@@ -61,6 +61,11 @@ func (e event) before(other event) bool {
 	return e.Ref.Compare(other.Ref) < 0
 }
 
+// equal returns true when event.Ref are equal.
+func (e event) equal(other event) bool {
+	return e.Ref.Equals(other.Ref)
+}
+
 // eventList is an in-memory representation of an Events shelf entry
 type eventList struct {
 	Events []event `json:"events"`
@@ -92,3 +97,12 @@ func (el *eventList) insert(newEvent event) int {
 	el.Events = newList
 	return index
 }
+
+func (el *eventList) contains(newEvent event) bool {
+	for _, e := range el.Events {
+		if e.equal(newEvent) {
+			return true
+		}
+	}
+	return false
+}

vdr/didstore/event_test.go

@@ -113,3 +113,18 @@ func TestEventList_insert(t *testing.T) {
 		assert.Equal(t, sha2s, el.Events[2].Ref)
 	})
 }
+
+func TestEventList_contains(t *testing.T) {
+	t.Run("false", func(t *testing.T) {
+		el := eventList{}
+
+		assert.False(t, el.contains(event{Ref: sha0s}))
+	})
+
+	t.Run("true", func(t *testing.T) {
+		el := eventList{}
+		el.insert(event{Ref: sha0s})
+
+		assert.True(t, el.contains(event{Ref: sha0s}))
+	})
+}

vdr/didstore/reader.go

@@ -88,12 +88,3 @@ func readEventList(tx stoabs.ReadTx, id did.DID) (eventList, error) {
 	}
 	return el, nil
 }
-
-func transactionExists(tx stoabs.ReadTx, ref hash.SHA256Hash) (bool, error) {
-	txReader := tx.GetShelfReader(transactionIndexShelf)
-	bytes, err := txReader.Get(stoabs.HashKey(ref))
-	if err != nil && !errors.Is(err, stoabs.ErrKeyNotFound) {
-		return false, err
-	}
-	return len(bytes) > 0, nil
-}

vdr/didstore/reader_test.go

@@ -96,38 +96,3 @@ func Test_readEventList(t *testing.T) {
 		require.NoError(t, err)
 	})
 }
-
-func Test_transactionExists(t *testing.T) {
-	store := NewTestStore(t)
-
-	t.Run("false", func(t *testing.T) {
-		err := store.db.Read(context.Background(), func(tx stoabs.ReadTx) error {
-			dup, _ := transactionExists(tx, hash.RandomHash())
-
-			assert.False(t, dup)
-
-			return nil
-		})
-		require.NoError(t, err)
-	})
-
-	t.Run("true", func(t *testing.T) {
-		transaction := newTestTransaction(did.Document{})
-
-		err := store.db.Write(context.Background(), func(tx stoabs.WriteTx) error {
-			txShelf := tx.GetShelfWriter(transactionIndexShelf)
-			_ = txShelf.Put(stoabs.HashKey(transaction.Ref), []byte{0})
-			return nil
-		})
-		require.NoError(t, err)
-
-		err = store.db.Read(context.Background(), func(tx stoabs.ReadTx) error {
-			dup, _ := transactionExists(tx, transaction.Ref)
-
-			assert.True(t, dup)
-
-			return nil
-		})
-		require.NoError(t, err)
-	})
-}

vdr/didstore/store.go

@@ -75,33 +75,40 @@ func (tl *store) Configure(_ core.ServerConfig) (err error) {
 // Add inserts the document version at the correct place and updates all later versions if needed
 // The integrity of the document has already been checked by the DAG.
 func (tl *store) Add(didDocument did.Document, transaction Transaction) error {
-	// prevents parallel execution
+	// First write the document and transaction to the transactionIndexShelf and documentShelf.
+	// This operation is duplicate save, since it uses hash values as key.
+	// This operation must succeed because otherwise the second transaction will be broken forever.
+	// Due to the way Redis works, there's no guarantee all the data is written transactionally when
+	// executed in a single write operation.
 	err := tl.db.Write(context.Background(), func(tx stoabs.WriteTx) error {
-		if exists, err := transactionExists(tx, transaction.Ref); err != nil {
-			return err
-		} else if exists {
-			return nil
+		// write document to documentShelf
+		err := writeDocument(tx, didDocument, transaction)
+		if err != nil {
+			return fmt.Errorf("writeDocument failed: %w", err)
 		}
+		return nil
+	}, stoabs.WithWriteLock())
+	if err != nil {
+		return fmt.Errorf("database error on commit: %w", err)
+	}
 
+	err = tl.db.Write(context.Background(), func(tx stoabs.WriteTx) error {
 		currentEventList, err := readEventList(tx, didDocument.ID)
 		if err != nil {
 			return fmt.Errorf("read eventList failed: %w", err)
 		}
 
-		// write document to documentShelf
-		err = writeDocument(tx, didDocument, transaction)
-		if err != nil {
-			return fmt.Errorf("writeDocument failed: %w", err)
+		transaction.document = &didDocument
+		if currentEventList.contains(event(transaction)) {
+			return nil
 		}
 
-		transaction.document = &didDocument
 		index := currentEventList.insert(event(transaction))
 		var base *event
 		applyList := currentEventList.Events[index:]
 		if index > 0 {
 			base = &currentEventList.Events[index-1]
 		}
-
 		if err = applyFrom(tx, base, applyList); err != nil {
 			return fmt.Errorf("applying event list failed: %w", err)
 		}

vdr/didstore/store_test.go

@@ -109,6 +109,37 @@ func TestStore_Add(t *testing.T) {
 		})
 	})
 
+	t.Run("duplicate ok", func(t *testing.T) {
+		store := NewTestStore(t)
+
+		require.NoError(t, store.Add(create, txCreate))
+		require.NoError(t, store.Add(create, txCreate))
+
+		err := store.db.ReadShelf(context.Background(), metadataShelf, func(reader stoabs.Reader) error {
+			metaBytes, err := reader.Get(stoabs.BytesKey(fmt.Sprintf("%s0", testDID.String())))
+			if err != nil {
+				return err
+			}
+			metadata := documentMetadata{}
+			err = json.Unmarshal(metaBytes, &metadata)
+			if err != nil {
+				return err
+			}
+
+			assert.Equal(t, txCreate.SigningTime.Unix(), metadata.Created.Unix())
+			assert.Equal(t, txCreate.SigningTime.Unix(), metadata.Updated.Unix())
+			assert.Nil(t, metadata.PreviousHash)
+			assert.Equal(t, txCreate.PayloadHash, metadata.Hash)
+			assert.Nil(t, metadata.PreviousTransaction)
+			assert.Equal(t, []hash.SHA256Hash{txCreate.Ref}, metadata.SourceTransactions)
+			assert.Equal(t, 0, metadata.Version)
+			assert.Equal(t, false, metadata.Deactivated)
+
+			return nil
+		})
+		require.NoError(t, err)
+	})
+
 	t.Run("update ok", func(t *testing.T) {
 		store := NewTestStore(t)