From 3f7232facaebc69fccdbc773c2cccb4a668089cd Mon Sep 17 00:00:00 2001
From: Tommy PAGEARD <tpageard@mailgun.com>
Date: Wed, 8 Jul 2020 14:21:49 +0200
Subject: [PATCH] feat(peer): add GetURL to be able to retrieve peer url

---
 groupcache.go      |  2 +-
 groupcache_test.go |  4 ++++
 http.go            | 14 ++++++++++++++
 peers.go           |  6 ++++++
 4 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/groupcache.go b/groupcache.go
index e841ef9..c583d80 100644
--- a/groupcache.go
+++ b/groupcache.go
@@ -353,7 +353,7 @@ func (g *Group) load(ctx context.Context, key string, dest Sink) (value ByteView
 					"err":      err,
 					"key":      key,
 					"category": "groupcache",
-				}).Error("error retrieving key from peers")
+				}).Errorf("error retrieving key from peer '%s'", g.peers.GetURL(key))
 			}
 
 			g.Stats.PeerErrors.Add(1)
diff --git a/groupcache_test.go b/groupcache_test.go
index a3d8369..58f8c81 100644
--- a/groupcache_test.go
+++ b/groupcache_test.go
@@ -285,6 +285,10 @@ func (p fakePeers) GetAll() []ProtoGetter {
 	return p
 }
 
+func (p fakePeers) GetURL(key string) string {
+	return "fakePeer"
+}
+
 // tests that peers (virtual, in-process) are hit, and how much.
 func TestPeers(t *testing.T) {
 	once.Do(testSetup)
diff --git a/http.go b/http.go
index a792357..badc84c 100644
--- a/http.go
+++ b/http.go
@@ -157,6 +157,20 @@ func (p *HTTPPool) PickPeer(key string) (ProtoGetter, bool) {
 	return nil, false
 }
 
+// GetURL
+func (p *HTTPPool) GetURL(key string) string {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	if p.peers.IsEmpty() {
+		return ""
+	}
+	if peer := p.peers.Get(key); peer != p.self {
+		return peer
+	}
+	return p.self
+}
+
 func (p *HTTPPool) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	// Parse request.
 	if !strings.HasPrefix(r.URL.Path, p.opts.BasePath) {
diff --git a/peers.go b/peers.go
index dbb8ae1..9f36e6b 100644
--- a/peers.go
+++ b/peers.go
@@ -20,6 +20,7 @@ package groupcache
 
 import (
 	"context"
+
 	pb "github.com/mailgun/groupcache/v2/groupcachepb"
 )
 
@@ -36,7 +37,11 @@ type PeerPicker interface {
 	// and true to indicate that a remote peer was nominated.
 	// It returns nil, false if the key owner is the current peer.
 	PickPeer(key string) (peer ProtoGetter, ok bool)
+	// GetAll returns all the peers in the group
 	GetAll() []ProtoGetter
+	// GetURL returns the peer URL that own the specific key
+	// It returns empty string if there is no peers
+	GetURL(key string) string
 }
 
 // NoPeers is an implementation of PeerPicker that never finds a peer.
@@ -44,6 +49,7 @@ type NoPeers struct{}
 
 func (NoPeers) PickPeer(key string) (peer ProtoGetter, ok bool) { return }
 func (NoPeers) GetAll() []ProtoGetter                           { return []ProtoGetter{} }
+func (NoPeers) GetURL(key string) string                        { return "" }
 
 var (
 	portPicker func(groupName string) PeerPicker