From 1d0523c46b7cfa844bfa3a3ca0b988107cdb4554 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Giedrius=20Statkevi=C4=8Dius?=
 <giedrius.statkevicius@vinted.com>
Date: Fri, 4 Aug 2023 13:38:27 +0300
Subject: [PATCH] store/bucket: wait until chunk loading ends in Close()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Chunk reader needs to wait until the chunk loading ends in Close()
because otherwise there will be a race between appending to r.chunkBytes
and reading from it.

Signed-off-by: Giedrius Statkevičius <giedrius.statkevicius@vinted.com>
---
 pkg/store/bucket.go | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/pkg/store/bucket.go b/pkg/store/bucket.go
index 09bfba32068..a4a214dc5ae 100644
--- a/pkg/store/bucket.go
+++ b/pkg/store/bucket.go
@@ -3160,6 +3160,9 @@ type bucketChunkReader struct {
 	mtx        sync.Mutex
 	stats      *queryStats
 	chunkBytes []*[]byte // Byte slice to return to the chunk pool on close.
+
+	loadingChunks     bool
+	finishLoadingChks chan struct{}
 }
 
 func newBucketChunkReader(block *bucketBlock) *bucketChunkReader {
@@ -3174,9 +3177,16 @@ func (r *bucketChunkReader) reset() {
 	for i := range r.toLoad {
 		r.toLoad[i] = r.toLoad[i][:0]
 	}
+	if r.finishLoadingChks != nil {
+		<-r.finishLoadingChks
+	}
+	r.finishLoadingChks = make(chan struct{})
 }
 
 func (r *bucketChunkReader) Close() error {
+	if r.loadingChunks {
+		<-r.finishLoadingChks
+	}
 	r.block.pendingReaders.Done()
 
 	for _, b := range r.chunkBytes {
@@ -3201,6 +3211,12 @@ func (r *bucketChunkReader) addLoad(id chunks.ChunkRef, seriesEntry, chunk int)
 
 // load loads all added chunks and saves resulting aggrs to refs.
 func (r *bucketChunkReader) load(ctx context.Context, res []seriesEntry, aggrs []storepb.Aggr, calculateChunkChecksum bool, bytesLimiter BytesLimiter) error {
+	r.loadingChunks = true
+	defer func() {
+		r.loadingChunks = false
+		close(r.finishLoadingChks)
+	}()
+
 	g, ctx := errgroup.WithContext(ctx)
 
 	for seq, pIdxs := range r.toLoad {