From ef790161db19e16ddf5c6514593b0d3da70c7bd9 Mon Sep 17 00:00:00 2001
From: Umputun <umputun@gmail.com>
Date: Sat, 9 Jun 2018 13:12:04 -0500
Subject: [PATCH] lock on votes, fix #77

---
 app/store/service/service.go      |  6 ++++++
 app/store/service/service_test.go | 32 +++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/app/store/service/service.go b/app/store/service/service.go
index b2b3c47d..c2ff0fe1 100644
--- a/app/store/service/service.go
+++ b/app/store/service/service.go
@@ -1,6 +1,7 @@
 package service
 
 import (
+	"sync"
 	"time"
 
 	"github.com/google/uuid"
@@ -16,6 +17,8 @@ type DataStore struct {
 	EditDuration   time.Duration
 	Secret         string
 	MaxCommentSize int
+
+	lock sync.Mutex
 }
 
 const defaultCommentMaxSize = 2000
@@ -53,6 +56,9 @@ func (s *DataStore) SetPin(locator store.Locator, commentID string, status bool)
 // Vote for comment by id and locator
 func (s *DataStore) Vote(locator store.Locator, commentID string, userID string, val bool) (comment store.Comment, err error) {
 
+	s.lock.Lock()
+	defer s.lock.Unlock()
+
 	comment, err = s.Get(locator, commentID)
 	if err != nil {
 		return comment, err
diff --git a/app/store/service/service_test.go b/app/store/service/service_test.go
index 94b18ce3..bbc66eb6 100644
--- a/app/store/service/service_test.go
+++ b/app/store/service/service_test.go
@@ -170,7 +170,39 @@ func TestService_VoteAggressive(t *testing.T) {
 	assert.Equal(t, 3, len(res))
 	t.Logf("%+v %d", res[0], res[0].Score)
 	assert.True(t, res[0].Score >= 0 && res[0].Score <= 2, "unexpected score %d", res[0].Score)
+}
 
+func TestService_VoteConcurrent(t *testing.T) {
+
+	defer os.Remove(testDb)
+	b := DataStore{Interface: prepStoreEngine(t)}
+
+	comment := store.Comment{
+		Text:    "text",
+		User:    store.User{IP: "192.168.1.1", ID: "user", Name: "name"},
+		Locator: store.Locator{URL: "https://radio-t.com", SiteID: "radio-t"},
+	}
+	_, err := b.Create(comment)
+	assert.NoError(t, err)
+	res, err := b.Last("radio-t", 0)
+	require.Nil(t, err)
+
+	// concurrent vote +1 as multiple users for the same comment
+	var wg sync.WaitGroup
+	for i := 0; i < 1000; i++ {
+		wg.Add(1)
+		i := i
+		go func() {
+			defer wg.Done()
+			b.Vote(store.Locator{URL: "https://radio-t.com", SiteID: "radio-t"}, res[0].ID, fmt.Sprintf("user1-%d", i), true)
+		}()
+	}
+	wg.Wait()
+	res, err = b.Last("radio-t", 0)
+	require.NoError(t, err)
+	t.Logf("%+v %d", res[0], res[0].Score)
+	assert.Equal(t, 1000, res[0].Score, "should have 1000 score")
+	assert.Equal(t, 1000, len(res[0].Votes), "should have 1000 votes")
 }
 
 func TestService_Pin(t *testing.T) {