From 876e5da4f818b490537a73e97bf078c2b44cf4f7 Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@soundcloud.com>
Date: Tue, 25 Oct 2016 14:59:33 +0200
Subject: [PATCH] Add guard against non-monotonic samples in series

This can only happen due to data corruption.
---
 storage/local/series.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/storage/local/series.go b/storage/local/series.go
index 05f0633d5..4acc40884 100644
--- a/storage/local/series.go
+++ b/storage/local/series.go
@@ -14,6 +14,7 @@
 package local
 
 import (
+	"fmt"
 	"sort"
 	"sync"
 	"time"
@@ -496,6 +497,10 @@ func (s *memorySeries) preloadChunksForRange(
 	if throughIdx == len(s.chunkDescs) {
 		throughIdx--
 	}
+	if fromIdx > throughIdx {
+		// Guard against nonsensical result. The caller will quarantine the series with a meaningful log entry.
+		return nopIter, fmt.Errorf("fromIdx=%d is greater than throughIdx=%d, likely caused by data corruption", fromIdx, throughIdx)
+	}
 
 	pinIndexes := make([]int, 0, throughIdx-fromIdx+1)
 	for i := fromIdx; i <= throughIdx; i++ {