chore(TSDB): add hooks for in-memory only tsdb creation

pkg/storage/stores/shipper/indexshipper/tsdb/builder.go

@@ -3,6 +3,7 @@ package tsdb
 import (
 	"context"
 	"fmt"
+	"io"
 	"math/rand"
 	"os"
 	"path/filepath"
@@ -111,12 +112,47 @@ func (b *Builder) Build(
 	name := fmt.Sprintf("%s-%x.staging", index.IndexFilename, rng)
 	tmpPath := filepath.Join(scratchDir, name)
 
-	var writer *index.Creator
+	writer, err := index.NewFileWriterWithVersion(ctx, b.version, tmpPath)
+	if err != nil {
+		return id, err
+	}
 
-	writer, err = index.NewWriterWithVersion(ctx, b.version, tmpPath)
+	if _, err := b.build(writer, false); err != nil {
+		return id, err
+	}
+
+	reader, err := index.NewFileReader(tmpPath)
 	if err != nil {
 		return id, err
 	}
+
+	from, through := reader.Bounds()
+
+	// load the newly compacted index to grab checksum, promptly close
+	dst := createFn(model.Time(from), model.Time(through), reader.Checksum())
+
+	reader.Close()
+	defer func() {
+		if err != nil {
+			os.RemoveAll(tmpPath)
+		}
+	}()
+
+	if err := chunk_util.EnsureDirectory(filepath.Dir(dst.Path())); err != nil {
+		return id, err
+	}
+	dstPath := dst.Path()
+	if err := os.Rename(tmpPath, dstPath); err != nil {
+		return id, err
+	}
+
+	return dst, nil
+}
+
+func (b *Builder) build(
+	writer *index.Creator,
+	reader bool, // whether to return the ReadCloser of the underlying DB
+) (io.ReadCloser, error) {
 	// TODO(owen-d): multithread
 
 	// Sort series
@@ -155,7 +191,7 @@ func (b *Builder) Build(
 	// Add symbols
 	for _, symbol := range symbols {
 		if err := writer.AddSymbol(symbol); err != nil {
-			return id, err
+			return nil, err
 		}
 	}
 
@@ -165,38 +201,45 @@ func (b *Builder) Build(
 			s.chunks = s.chunks.Finalize()
 		}
 		if err := writer.AddSeries(storage.SeriesRef(i), s.labels, s.fp, s.chunks...); err != nil {
-			return id, err
+			return nil, err
 		}
 	}
 
-	if _, err := writer.Close(false); err != nil {
-		return id, err
-	}
+	return writer.Close(reader)
+}
 
-	reader, err := index.NewFileReader(tmpPath)
+func (b *Builder) BuildInMemory(
+	ctx context.Context,
+	// Determines how to create the resulting Identifier and file name.
+	// This is variable as we use Builder for multiple reasons,
+	// such as building multi-tenant tsdbs on the ingester
+	// and per tenant ones during compaction
+	createFn func(from, through model.Time, checksum uint32) Identifier,
+) (id Identifier, data []byte, err error) {
+	writer, err := index.NewMemWriterWithVersion(ctx, b.version)
 	if err != nil {
-		return id, err
+		return id, nil, err
 	}
 
-	from, through := reader.Bounds()
-
-	// load the newly compacted index to grab checksum, promptly close
-	dst := createFn(model.Time(from), model.Time(through), reader.Checksum())
-
-	reader.Close()
-	defer func() {
-		if err != nil {
-			os.RemoveAll(tmpPath)
-		}
-	}()
+	readCloser, err := b.build(writer, true)
+	if err != nil {
+		return id, nil, err
+	}
+	defer readCloser.Close()
 
-	if err := chunk_util.EnsureDirectory(filepath.Dir(dst.Path())); err != nil {
-		return id, err
+	data, err = io.ReadAll(readCloser)
+	if err != nil {
+		return nil, nil, err
 	}
-	dstPath := dst.Path()
-	if err := os.Rename(tmpPath, dstPath); err != nil {
-		return id, err
+
+	reader, err := index.NewReader(index.RealByteSlice(data))
+	if err != nil {
+		return id, nil, err
 	}
+	defer reader.Close()
 
-	return dst, nil
+	from, through := reader.Bounds()
+	id = createFn(model.Time(from), model.Time(through), reader.Checksum())
+
+	return id, data, nil
 }

pkg/storage/stores/shipper/indexshipper/tsdb/index/index.go

@@ -211,7 +211,8 @@ func NewTOCFromByteSlice(bs ByteSlice) (*TOC, error) {
 	}, nil
 }
 
-func NewWriterWithVersion(ctx context.Context, version int, fn string) (*Creator, error) {
+// For writing TSDBs using temporary files
+func NewFileWriterWithVersion(ctx context.Context, version int, fn string) (*Creator, error) {
 	dir := filepath.Dir(fn)
 
 	df, err := fileutil.OpenDir(dir)
@@ -243,12 +244,39 @@ func NewWriterWithVersion(ctx context.Context, version int, fn string) (*Creator
 		return nil, errors.Wrap(err, "sync dir")
 	}
 
+	return newWriter(
+		ctx,
+		version,
+		f,
+		fP,
+		fPO,
+	)
+}
+
+// For writing TSDBs in memory
+func NewMemWriterWithVersion(ctx context.Context, version int) (*Creator, error) {
+	return newWriter(
+		ctx,
+		version,
+		NewBufferWriter(),
+		NewBufferWriter(),
+		NewBufferWriter(),
+	)
+}
+
+func newWriter(
+	ctx context.Context,
+	version int,
+	fWriter writer,
+	postingsWriter writer,
+	postingOffsetsWriter writer,
+) (*Creator, error) {
 	iw := &Creator{
 		Version: version,
 		ctx:     ctx,
-		f:       f,
-		fP:      fP,
-		fPO:     fPO,
+		f:       fWriter,
+		fP:      postingsWriter,
+		fPO:     postingOffsetsWriter,
 		stage:   idxStageNone,
 
 		// Reusable memory.
@@ -267,7 +295,7 @@ func NewWriterWithVersion(ctx context.Context, version int, fn string) (*Creator
 
 // NewWriter returns a new Writer to the given filename.
 func NewWriter(ctx context.Context, indexFormat int, fn string) (*Creator, error) {
-	return NewWriterWithVersion(ctx, indexFormat, fn)
+	return NewFileWriterWithVersion(ctx, indexFormat, fn)
 }
 
 func (w *Creator) write(bufs ...[]byte) error {

pkg/storage/stores/shipper/indexshipper/tsdb/index/index_test.go

@@ -727,7 +727,7 @@ func TestDecoder_ChunkSamples(t *testing.T) {
 		},
 	} {
 		t.Run(name, func(t *testing.T) {
-			iw, err := NewWriterWithVersion(context.Background(), FormatV2, filepath.Join(dir, name))
+			iw, err := NewFileWriterWithVersion(context.Background(), FormatV2, filepath.Join(dir, name))
 			require.NoError(t, err)
 
 			syms := []string{}