Expose translation mvcc (#2381)

* expose Transaction on TranslateStore for DAX Snapshotting

* try to fix ramdisk nonsense

apparently, we were running in either a shell env or docker env
randomly, so this could sometimes pass and sometimes fail since the
shell env had the ramdisk set up and docker didn't.

Now we force to run in docker always and set up ramdisk explicitly.

* debug ramdisk issue?

* fix tests... and a buncha other stuff

The executor test I modified failed when I changed DefaultPartitionN
to 8, but just because stuff was out of order so I made it more
robust.

I edited some data gen stuff to make shorter lines because it was
making grep results unusable.

the actual fix is in translate_boltdb_test.go

* clean up, fix code review feedback

(cherry picked from commit 3693b9950a)

Makefile

@@ -77,9 +77,9 @@ testvsub:
 			echo; echo "999 done testing subpkg $$pkg"; \
 		done
 
-# make a 2GB RAMDisk. Speed up tests by running them with RAMDISK=/mnt/ramfs
+# make a 2GB RAMDisk. Speed up tests by running them with RAMDISK=/mnt/ramdisk
 ramdisk-linux:
-	mount -o size=2G -t tmpfs none /mnt/ramfs
+	mount -o size=2G -t tmpfs none /mnt/ramdisk
 
 # make a 2GB RAMDisk. Speed up tests by running them with RAMDISK=/Volumes/RAMDisk
 ramdisk-osx:

api.go

@@ -967,7 +967,7 @@ func (r RedirectError) Error() string {
 }
 
 // TranslateData returns all translation data in the specified partition.
-func (api *API) TranslateData(ctx context.Context, indexName string, partition int) (io.WriterTo, error) {
+func (api *API) TranslateData(ctx context.Context, indexName string, partition int) (TranslateStore, error) {
 	span, _ := tracing.StartSpanFromContext(ctx, "API.TranslateData")
 	defer span.Finish()
 
@@ -1022,7 +1022,7 @@ func (api *API) TranslateData(ctx context.Context, indexName string, partition i
 }
 
 // FieldTranslateData returns all translation data in the specified field.
-func (api *API) FieldTranslateData(ctx context.Context, indexName, fieldName string) (io.WriterTo, error) {
+func (api *API) FieldTranslateData(ctx context.Context, indexName, fieldName string) (TranslateStore, error) {
 	span, _ := tracing.StartSpanFromContext(ctx, "API.FieldTranslateData")
 	defer span.Finish()
 	if err := api.validate(apiFieldTranslateData); err != nil {
@@ -3136,18 +3136,22 @@ func (api *API) SnapshotTableKeys(ctx context.Context, req *dax.SnapshotTableKey
 	qtid := req.TableKey.QualifiedTableID()
 
 	// Create the snapshot for the current version.
-	wrTo, err := api.TranslateData(ctx, string(req.TableKey), int(req.PartitionNum))
+	trans, err := api.TranslateData(ctx, string(req.TableKey), int(req.PartitionNum))
 	if err != nil {
-		return errors.Wrapf(err, "getting index/partition writeto: %s/%d", req.TableKey, req.PartitionNum)
+		return errors.Wrapf(err, "getting index/partition translate store: %s/%d", req.TableKey, req.PartitionNum)
 	}
+	// get a write tx to ensure no other writes while incrementing WL version.
+	wrTo, err := trans.Begin(true)
+	if err != nil {
+		return errors.Wrap(err, "beginning table translate write tx")
+	}
+	defer wrTo.Rollback()
 
-	// TODO(jaffee) need to ensure writes to translation data can't
-	// occur while this is happening.
 	resource := api.serverlessStorage.GetTableKeyResource(qtid, req.PartitionNum)
 	if err := resource.IncrementWLVersion(); err != nil {
 		return errors.Wrap(err, "incrementing write log version")
 	}
-	// TODO(jaffee) downgrade (currently non-existent) lock to read-only
+	// TODO(jaffee) downgrade write tx to read-only
 	err = resource.SnapshotTo(wrTo)
 	return errors.Wrap(err, "snapshotting table keys")
 }
@@ -3158,17 +3162,22 @@ func (api *API) SnapshotFieldKeys(ctx context.Context, req *dax.SnapshotFieldKey
 	qtid := req.TableKey.QualifiedTableID()
 
 	// Create the snapshot for the current version.
-	// TODO(jaffee) change this to get write lock
-	wrTo, err := api.FieldTranslateData(ctx, string(req.TableKey), string(req.Field))
+	trans, err := api.FieldTranslateData(ctx, string(req.TableKey), string(req.Field))
 	if err != nil {
 		return errors.Wrap(err, "getting index/field writeto")
 	}
+	// get a write tx to ensure no other writes while incrementing WL version.
+	wrTo, err := trans.Begin(true)
+	if err != nil {
+		return errors.Wrap(err, "beginning field translate write tx")
+	}
+	defer wrTo.Rollback()
 
 	resource := api.serverlessStorage.GetFieldKeyResource(qtid, req.Field)
 	if err := resource.IncrementWLVersion(); err != nil {
 		return errors.Wrap(err, "incrementing writelog version")
 	}
-	// TODO(jaffee) downgrade to read lock
+	// TODO(jaffee) downgrade to read tx
 	err = resource.SnapshotTo(wrTo)
 	return errors.Wrap(err, "snapshotTo in FieldKeys")
 }

executor_test.go

@@ -5132,47 +5132,50 @@ func TestExecutor_Execute_Extract_Keyed(t *testing.T) {
 	`)
 
 	resp := c.Query(t, c.Idx(), `Extract(All(), Rows(set))`)
-	expect := []interface{}{
-		pilosa.ExtractedTable{
-			Fields: []pilosa.ExtractedTableField{
-				{
-					Name: "set",
-					Type: "[]uint64",
+	expect := pilosa.ExtractedTable{
+		Fields: []pilosa.ExtractedTableField{
+			{
+				Name: "set",
+				Type: "[]uint64",
+			},
+		},
+		// The order of these probably shouldn't matter, but currently depends indirectly on the
+		// index.
+		Columns: []pilosa.ExtractedTableColumn{
+			{
+				Column: pilosa.KeyOrID{Keyed: true, Key: "h"},
+				Rows: []interface{}{
+					[]uint64{
+						1,
+						2,
+					},
 				},
 			},
-			// The order of these probably shouldn't matter, but currently depends indirectly on the
-			// index.
-			Columns: []pilosa.ExtractedTableColumn{
-				{
-					Column: pilosa.KeyOrID{Keyed: true, Key: "h"},
-					Rows: []interface{}{
-						[]uint64{
-							1,
-							2,
-						},
+			{
+				Column: pilosa.KeyOrID{Keyed: true, Key: "xyzzy"},
+				Rows: []interface{}{
+					[]uint64{
+						2,
 					},
 				},
-				{
-					Column: pilosa.KeyOrID{Keyed: true, Key: "xyzzy"},
-					Rows: []interface{}{
-						[]uint64{
-							2,
-						},
-					},
-				},
-				{
-					Column: pilosa.KeyOrID{Keyed: true, Key: "plugh"},
-					Rows: []interface{}{
-						[]uint64{},
-					},
+			},
+			{
+				Column: pilosa.KeyOrID{Keyed: true, Key: "plugh"},
+				Rows: []interface{}{
+					[]uint64{},
 				},
 			},
 		},
 	}
 
-	if !reflect.DeepEqual(expect, resp.Results) {
-		t.Errorf("expected %v but got %v", expect, resp.Results)
+	if len(resp.Results) != 1 {
+		t.Fail()
 	}
+	res := resp.Results[0].(pilosa.ExtractedTable)
+	if !reflect.DeepEqual(expect.Fields, res.Fields) {
+		t.Errorf("expected:\n%v\nbut got:\n%v", expect, resp.Results)
+	}
+	assert.ElementsMatch(t, expect.Columns, res.Columns)
 }
 
 func TestExecutor_Execute_MaxMemory(t *testing.T) {
@@ -7429,6 +7432,7 @@ func backupCluster(t *testing.T, c *test.Cluster, index string) (backupDir strin
 
 	buf := &bytes.Buffer{}
 	backupLog := logger.NewStandardLogger(buf)
+
 	backupCommand := ctl.NewBackupCommand(backupLog)
 	backupCommand.Host = c.Nodes[len(c.Nodes)-1].URL() // don't pick node 0 so we don't always get primary (better code coverage)
 	backupCommand.Index = index

http_handler.go

@@ -2790,8 +2790,15 @@ func (h *Handler) handleGetTranslateData(w http.ResponseWriter, r *http.Request)
 			http.Error(w, err.Error(), http.StatusNotFound)
 			return
 		}
+		tx, err := p.Begin(false)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		defer tx.Rollback()
+
 		// Stream translate data to response body.
-		if _, err := p.WriteTo(w); err != nil {
+		if _, err := tx.WriteTo(w); err != nil {
 			h.logger.Errorf("error streaming translation data: %s", err)
 		}
 		return
@@ -2816,8 +2823,14 @@ func (h *Handler) handleGetTranslateData(w http.ResponseWriter, r *http.Request)
 		http.Error(w, err.Error(), http.StatusNotFound)
 		return
 	}
+	tx, err := p.Begin(false)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	defer tx.Rollback()
 	// Stream translate partition to response body.
-	if _, err := p.WriteTo(w); err != nil {
+	if _, err := tx.WriteTo(w); err != nil {
 		h.logger.Errorf("error streaming translation data: %s", err)
 	}
 }

translate.go

@@ -76,9 +76,7 @@ type TranslateStore interface { // TODO: refactor this interface; readonly shoul
 	// Returns a reader from the given ID offset.
 	EntryReader(ctx context.Context, offset uint64) (TranslateEntryReader, error)
 
-	// WriteTo ensures that the TranslateStore implements io.WriterTo.
-	// It should write the contents of the store to the writer.
-	WriteTo(io.Writer) (int64, error)
+	Begin(write bool) (TranslatorTx, error)
 
 	// ReadFrom ensures that the TranslateStore implements io.ReaderFrom.
 	// It should read from the reader and replace the data store with
@@ -88,6 +86,16 @@ type TranslateStore interface { // TODO: refactor this interface; readonly shoul
 	Delete(records *roaring.Bitmap) (Commitor, error)
 }
 
+// TranslatorTx reproduces a subset of the methods on the BoltDB Tx
+// object. Others may be needed in the future and we should just add
+// them here. The idea is not to scatter direct references to bolt
+// stuff throughout the whole codebase.
+type TranslatorTx interface {
+	WriteTo(io.Writer) (int64, error)
+	Rollback() error
+	// e.g. Commit() error
+}
+
 // OpenTranslateStoreFunc represents a function for instantiating and opening a TranslateStore.
 type OpenTranslateStoreFunc func(path, index, field string, partitionID, partitionN int, fsyncEnabled bool) (TranslateStore, error)
 

translate_boltdb.go

@@ -396,14 +396,9 @@ func (s *BoltTranslateStore) MaxID() (max uint64, err error) {
 	return max, nil
 }
 
-// WriteTo writes the contents of the store to the writer.
-func (s *BoltTranslateStore) WriteTo(w io.Writer) (int64, error) {
-	tx, err := s.db.Begin(false)
-	if err != nil {
-		return 0, err
-	}
-	defer func() { _ = tx.Rollback() }()
-	return tx.WriteTo(w)
+// Begin starts and returns a transaction on the underlying store.
+func (s *BoltTranslateStore) Begin(write bool) (TranslatorTx, error) {
+	return s.db.Begin(write)
 }
 
 // ReadFrom reads the content and overwrites the existing store.

translate_boltdb_test.go

@@ -458,12 +458,19 @@ func TestTranslateStore_ReadWrite(t *testing.T) {
 		buf := bytes.NewBuffer(nil)
 		expN := s.Size()
 
-		// After this, the buffer should contain batch0.
-		if n, err := s.WriteTo(buf); err != nil {
-			t.Fatalf("writing to buffer: %s", err)
-		} else if n != expN {
-			t.Fatalf("expected buffer size: %d, but got: %d", expN, n)
-		}
+		// wrap in a func so we can defer rollback. Need rollback to
+		// happen before the end of the test. I'm not entirely sure
+		// why, but it hangs if you don't.
+		func() {
+			tx, err := s.Begin(false)
+			require.NoError(t, err)
+			defer tx.Rollback()
+
+			// After this, the buffer should contain batch0.
+			n, err := tx.WriteTo(buf)
+			require.NoError(t, err)
+			require.Equal(t, expN, n)
+		}()
 
 		// Populate the store with the keys in batch1.
 		batch1IDs, err := s.CreateKeys(batch1...)