From 17d08c1fe09d0fc312b53468da3e723b02418099 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Fri, 22 Nov 2019 16:10:33 +0200
Subject: [PATCH] app/vmselect: adjust `end` arg instead of adjusting `start`
 arg if start > end

`start` arg has higher chances to be set properly comparing to `end` arg,
so it is expected that the `end` arg could be adjusted if it was set incorrectly.
---
 app/vmselect/prometheus/prometheus.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/app/vmselect/prometheus/prometheus.go b/app/vmselect/prometheus/prometheus.go
index 46bf576c94..dd7ee8b713 100644
--- a/app/vmselect/prometheus/prometheus.go
+++ b/app/vmselect/prometheus/prometheus.go
@@ -140,7 +140,7 @@ func ExportHandler(at *auth.Token, w http.ResponseWriter, r *http.Request) error
 	format := r.FormValue("format")
 	deadline := getDeadline(r)
 	if start >= end {
-		start = end - defaultStep
+		end = start + defaultStep
 	}
 	if err := exportHandler(at, w, matches, start, end, format, deadline); err != nil {
 		return err
@@ -343,7 +343,7 @@ func labelValuesWithMatches(at *auth.Token, labelName string, matches []string,
 		return nil, false, err
 	}
 	if start >= end {
-		start = end - defaultStep
+		end = start + defaultStep
 	}
 	sq := &storage.SearchQuery{
 		AccountID:    at.AccountID,
@@ -478,7 +478,7 @@ func SeriesHandler(at *auth.Token, w http.ResponseWriter, r *http.Request) error
 		return err
 	}
 	if start >= end {
-		start = end - defaultStep
+		end = start + defaultStep
 	}
 	sq := &storage.SearchQuery{
 		AccountID:    at.AccountID,
@@ -642,7 +642,7 @@ func QueryRangeHandler(at *auth.Token, w http.ResponseWriter, r *http.Request) e
 		return fmt.Errorf(`too long query; got %d bytes; mustn't exceed %d bytes`, len(query), *maxQueryLen)
 	}
 	if start > end {
-		start = end
+		end = start + defaultStep
 	}
 	if err := promql.ValidateMaxPointsPerTimeseries(start, end, step); err != nil {
 		return err