From ec0b8b42f240525a315aa55671877ce77e3a9d70 Mon Sep 17 00:00:00 2001
From: Arul Ajmani <arulajmani@gmail.com>
Date: Thu, 26 Sep 2024 17:25:30 +0000
Subject: [PATCH] kvnemesis: ignore SysBytes:{,-}10 MVCC stats discrepancy

We started ignoring these in 398dfc7. However, that commit was
effectively reverted when we addressed #93896 in 2d855d3. However, like
2d855d3 notes in its description, this was best effort. As such, this
can still cause test flakes (e.g. #131187).

This patch effectively resurrects 398dfc7, but also additionally
quietens `SysBytes:-10` failure mdoes.

Epic: none

Release note: None
---
 pkg/kv/kvnemesis/env.go | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/pkg/kv/kvnemesis/env.go b/pkg/kv/kvnemesis/env.go
index 9aa39d77f935..1a2afa5da786 100644
--- a/pkg/kv/kvnemesis/env.go
+++ b/pkg/kv/kvnemesis/env.go
@@ -14,6 +14,7 @@ import (
 	"context"
 	gosql "database/sql"
 	"fmt"
+	"regexp"
 	"time"
 
 	"github.com/cockroachdb/cockroach-go/v2/crdb"
@@ -68,6 +69,23 @@ func (e *Env) CheckConsistency(ctx context.Context, span roachpb.Span) []error {
 		if err := rows.Scan(&rangeID, &key, &status, &detail); err != nil {
 			return []error{err}
 		}
+		// NB: There's a known issue that can result in a 10-byte discrepancy in
+		// SysBytes. See:
+		// https://github.com/cockroachdb/cockroach/issues/93896
+		//
+		// This isn't critical, so we ignore such discrepancies.
+		if status == kvpb.CheckConsistencyResponse_RANGE_CONSISTENT_STATS_INCORRECT.String() {
+			m := regexp.MustCompile(`.*\ndelta \(stats-computed\): \{(.*)\}`).FindStringSubmatch(detail)
+			if len(m) > 1 {
+				delta := m[1]
+				// Strip out LastUpdateNanos and all zero-valued fields.
+				delta = regexp.MustCompile(`LastUpdateNanos:\d+`).ReplaceAllString(delta, "")
+				delta = regexp.MustCompile(`\S+:0\b`).ReplaceAllString(delta, "")
+				if regexp.MustCompile(`^\s*SysBytes:-?10\s*$`).MatchString(delta) {
+					continue
+				}
+			}
+		}
 		switch status {
 		case kvpb.CheckConsistencyResponse_RANGE_INDETERMINATE.String():
 			// Can't do anything, so let it slide.