From e205975716cd3b4dcb48baef7e01516cdf9ecdf5 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Tue, 10 Nov 2020 16:11:16 +0200
Subject: [PATCH] lib/promscrape: make a copy of ScrapeWork from discovered
 []ScrapeWork slice instead of referring to an item in this slice

This should prevent from holding previously discovered []ScrapeWork slices when a part of discovered targets changes over time.
This should reduce memory usage for the case when big number of discovered scrape targets changes over time.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/825
---
 docs/CHANGELOG.md              | 2 ++
 lib/promscrape/targetstatus.go | 6 +++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 07b827338..f85c48a97 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 # tip
 
+* FEATURE: vmagent: reduce memory usage when service discovery detects big number of scrape targets and the set of discovered targets changes over time.
+  See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/825
 * FEATURE: vmagent: add `-promscrape.dropOriginalLabels` command-line option, which can be used for reducing memory usage when scraping big number of targets.
   See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/825#issuecomment-724308361 for details.
 * FEATURE: vmalert: explicitly set extra labels to alert entities. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/870
diff --git a/lib/promscrape/targetstatus.go b/lib/promscrape/targetstatus.go
index cb4c8c0af..6479d581c 100644
--- a/lib/promscrape/targetstatus.go
+++ b/lib/promscrape/targetstatus.go
@@ -64,7 +64,7 @@ func (tsm *targetStatusMap) Reset() {
 func (tsm *targetStatusMap) Register(sw *ScrapeWork) {
 	tsm.mu.Lock()
 	tsm.m[sw.ID] = targetStatus{
-		sw: sw,
+		sw: *sw,
 	}
 	tsm.mu.Unlock()
 }
@@ -78,7 +78,7 @@ func (tsm *targetStatusMap) Unregister(sw *ScrapeWork) {
 func (tsm *targetStatusMap) Update(sw *ScrapeWork, group string, up bool, scrapeTime, scrapeDuration int64, err error) {
 	tsm.mu.Lock()
 	tsm.m[sw.ID] = targetStatus{
-		sw:             sw,
+		sw:             *sw,
 		up:             up,
 		scrapeGroup:    group,
 		scrapeTime:     scrapeTime,
@@ -221,7 +221,7 @@ type jobStatus struct {
 }
 
 type targetStatus struct {
-	sw             *ScrapeWork
+	sw             ScrapeWork
 	up             bool
 	scrapeGroup    string
 	scrapeTime     int64