From 767c0709b18c17179ad6f77e843db3b6bbd88999 Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@soundcloud.com>
Date: Fri, 6 Jan 2017 18:43:41 +0100
Subject: [PATCH] Retrieval: Avoid copying Target

retreival.Target contains a mutex. It was copied in the Targets()
call. This potentially can wreak a lot of havoc.

It might even have caused the issues reported as #2266 and #2262 .
---
 retrieval/targetmanager.go |  6 +++---
 web/api/v1/api.go          |  2 +-
 web/api/v1/api_test.go     | 10 +++++-----
 web/web.go                 |  4 ++--
 4 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/retrieval/targetmanager.go b/retrieval/targetmanager.go
index 48d641185..28e387a96 100644
--- a/retrieval/targetmanager.go
+++ b/retrieval/targetmanager.go
@@ -132,16 +132,16 @@ func (tm *TargetManager) reload() {
 }
 
 // Targets returns the targets currently being scraped bucketed by their job name.
-func (tm *TargetManager) Targets() []Target {
+func (tm *TargetManager) Targets() []*Target {
 	tm.mtx.RLock()
 	defer tm.mtx.RUnlock()
 
-	targets := []Target{}
+	targets := []*Target{}
 	for _, ps := range tm.targetSets {
 		ps.sp.mtx.RLock()
 
 		for _, t := range ps.sp.targets {
-			targets = append(targets, *t)
+			targets = append(targets, t)
 		}
 
 		ps.sp.mtx.RUnlock()
diff --git a/web/api/v1/api.go b/web/api/v1/api.go
index 340a6c58f..152091aab 100644
--- a/web/api/v1/api.go
+++ b/web/api/v1/api.go
@@ -68,7 +68,7 @@ func (e *apiError) Error() string {
 }
 
 type targetRetriever interface {
-	Targets() []retrieval.Target
+	Targets() []*retrieval.Target
 }
 
 type response struct {
diff --git a/web/api/v1/api_test.go b/web/api/v1/api_test.go
index daf8a6819..27343edb6 100644
--- a/web/api/v1/api_test.go
+++ b/web/api/v1/api_test.go
@@ -33,9 +33,9 @@ import (
 	"github.com/prometheus/prometheus/retrieval"
 )
 
-type targetRetrieverFunc func() []retrieval.Target
+type targetRetrieverFunc func() []*retrieval.Target
 
-func (f targetRetrieverFunc) Targets() []retrieval.Target {
+func (f targetRetrieverFunc) Targets() []*retrieval.Target {
 	return f()
 }
 
@@ -57,9 +57,9 @@ func TestEndpoints(t *testing.T) {
 
 	now := model.Now()
 
-	tr := targetRetrieverFunc(func() []retrieval.Target {
-		return []retrieval.Target{
-			*retrieval.NewTarget(
+	tr := targetRetrieverFunc(func() []*retrieval.Target {
+		return []*retrieval.Target{
+			retrieval.NewTarget(
 				model.LabelSet{
 					model.SchemeLabel:      "http",
 					model.AddressLabel:     "example.com:8080",
diff --git a/web/web.go b/web/web.go
index 3d16e09d0..2469c27c7 100644
--- a/web/web.go
+++ b/web/web.go
@@ -373,14 +373,14 @@ func (h *Handler) rules(w http.ResponseWriter, r *http.Request) {
 
 func (h *Handler) targets(w http.ResponseWriter, r *http.Request) {
 	// Bucket targets by job label
-	tps := map[string][]retrieval.Target{}
+	tps := map[string][]*retrieval.Target{}
 	for _, t := range h.targetManager.Targets() {
 		job := string(t.Labels()[model.JobLabel])
 		tps[job] = append(tps[job], t)
 	}
 
 	h.executeTemplate(w, "targets.html", struct {
-		TargetPools map[string][]retrieval.Target
+		TargetPools map[string][]*retrieval.Target
 	}{
 		TargetPools: tps,
 	})