From 260cd84d8f8bc8d8545a79cf538470627f3c1642 Mon Sep 17 00:00:00 2001
From: frbimo <fr.bimo@gmail.com>
Date: Wed, 14 Oct 2020 21:29:59 +0800
Subject: [PATCH] log on empty head compaction result (#8037)

Signed-off-by: frbimo <fr.bimo@gmail.com>
---
 tsdb/compact.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tsdb/compact.go b/tsdb/compact.go
index 74f54fdb9c..fbc5b35833 100644
--- a/tsdb/compact.go
+++ b/tsdb/compact.go
@@ -488,6 +488,12 @@ func (c *LeveledCompactor) Write(dest string, b BlockReader, mint, maxt int64, p
 	}
 
 	if meta.Stats.NumSamples == 0 {
+		level.Info(c.logger).Log(
+			"msg", "write block resulted in empty block",
+			"mint", meta.MinTime,
+			"maxt", meta.MaxTime,
+			"duration", time.Since(start),
+		)
 		return ulid.ULID{}, nil
 	}