From 7f896dc907e4b871fff0853e3b6f7f145c7ef8cb Mon Sep 17 00:00:00 2001
From: Max Kotliar <mkotlyar@victoriametrics.com>
Date: Wed, 13 May 2026 14:34:12 +0300
Subject: [PATCH] address review comment

---
 lib/persistentqueue/fastqueue.go | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/lib/persistentqueue/fastqueue.go b/lib/persistentqueue/fastqueue.go
index e829bb6a4e..bc534be716 100644
--- a/lib/persistentqueue/fastqueue.go
+++ b/lib/persistentqueue/fastqueue.go
@@ -238,7 +238,7 @@ func (fq *FastQueue) MustReadBlock(dst []byte) ([]byte, bool) {
 			return dst, false
 		}
 		if len(fq.ch) > 0 {
-			return fq.mustReadInMemoryBlockLocked(dst)
+			return fq.mustReadInMemoryBlockLocked(dst), true
 		}
 		if n := fq.pq.GetPendingBytes(); n > 0 {
 			data, ok := fq.pq.MustReadBlockNonblocking(dst)
@@ -261,22 +261,26 @@ func (fq *FastQueue) MustReadInMemoryBlock(dst []byte) ([]byte, bool) {
 	fq.mu.Lock()
 	defer fq.mu.Unlock()
 
-	return fq.mustReadInMemoryBlockLocked(dst)
+	if len(fq.ch) > 0 {
+		return fq.mustReadInMemoryBlockLocked(dst), true
+	}
+
+	return nil, false
 }
 
-func (fq *FastQueue) mustReadInMemoryBlockLocked(dst []byte) ([]byte, bool) {
+func (fq *FastQueue) mustReadInMemoryBlockLocked(dst []byte) []byte {
 	if len(fq.ch) == 0 {
-		return dst, false
+		logger.Panicf("BUG: the function must not be called when in-memory queue is empty. Caller should verify the queue len upfront")
 	}
 	if n := fq.pq.GetPendingBytes(); n > 0 {
-		logger.Panicf("BUG: the file-based queue must be empty when the inmemory queue is non-empty; it contains %d pending bytes", n)
+		logger.Panicf("BUG: the file-based queue must be empty when the in-memory queue is non-empty; it contains %d pending bytes", n)
 	}
 	bb := <-fq.ch
 	fq.pendingInmemoryBytes -= uint64(len(bb.B))
 	fq.lastInmemoryBlockReadTime = fasttime.UnixTimestamp()
 	dst = append(dst, bb.B...)
 	blockBufPool.Put(bb)
-	return dst, true
+	return dst
 }
 
 // Dirname returns the directory name for persistent queue.