From acec15ebc6f57541d7abdd9fa6aa98dda0801e04 Mon Sep 17 00:00:00 2001
From: Derek Chiang <derekchiang93@gmail.com>
Date: Wed, 18 Jan 2017 08:21:07 -0800
Subject: [PATCH 1/2] clientv3/concurrency: fix rev comparison on concurrent
 key deletion

---
 clientv3/concurrency/stm.go | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/clientv3/concurrency/stm.go b/clientv3/concurrency/stm.go
index 056ebfb75..83333b932 100644
--- a/clientv3/concurrency/stm.go
+++ b/clientv3/concurrency/stm.go
@@ -249,11 +249,10 @@ func (s *stmReadCommitted) commit() *v3.TxnResponse {
 }
 
 func isKeyCurrent(k string, r *v3.GetResponse) v3.Cmp {
-	rev := r.Header.Revision + 1
 	if len(r.Kvs) != 0 {
-		rev = r.Kvs[0].ModRevision + 1
+		return v3.Compare(v3.ModRevision(k), "=", r.Kvs[0].ModRevision)
 	}
-	return v3.Compare(v3.ModRevision(k), "<", rev)
+	return v3.Compare(v3.ModRevision(k), "=", 0)
 }
 
 func respToValue(resp *v3.GetResponse) string {

From a94d20d1e46fe4f4c3c5d447c6c86c6b8f17572c Mon Sep 17 00:00:00 2001
From: Gyu-Ho Lee <gyuhox@gmail.com>
Date: Thu, 19 Jan 2017 21:04:58 -0800
Subject: [PATCH 2/2] integration: test STM apply on concurrent deletion

---
 integration/v3_stm_test.go | 47 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/integration/v3_stm_test.go b/integration/v3_stm_test.go
index 914a9dec8..e0c751b5d 100644
--- a/integration/v3_stm_test.go
+++ b/integration/v3_stm_test.go
@@ -197,3 +197,50 @@ func TestSTMSerialize(t *testing.T) {
 		}
 	}
 }
+
+// TestSTMApplyOnConcurrentDeletion ensures that concurrent key deletion
+// fails the first GET revision comparison within STM; trigger retry.
+func TestSTMApplyOnConcurrentDeletion(t *testing.T) {
+	clus := NewClusterV3(t, &ClusterConfig{Size: 1})
+	defer clus.Terminate(t)
+
+	etcdc := clus.RandClient()
+	if _, err := etcdc.Put(context.TODO(), "foo", "bar"); err != nil {
+		t.Fatal(err)
+	}
+	donec, readyc := make(chan struct{}), make(chan struct{})
+	go func() {
+		<-readyc
+		if _, err := etcdc.Delete(context.TODO(), "foo"); err != nil {
+			t.Fatal(err)
+		}
+		close(donec)
+	}()
+
+	try := 0
+	applyf := func(stm concurrency.STM) error {
+		try++
+		stm.Get("foo")
+		if try == 1 {
+			// trigger delete to make GET rev comparison outdated
+			close(readyc)
+			<-donec
+		}
+		stm.Put("foo2", "bar2")
+		return nil
+	}
+	if _, err := concurrency.NewSTMRepeatable(context.TODO(), etcdc, applyf); err != nil {
+		t.Fatalf("error on stm txn (%v)", err)
+	}
+	if try != 2 {
+		t.Fatalf("STM apply expected to run twice, got %d", try)
+	}
+
+	resp, err := etcdc.Get(context.TODO(), "foo2")
+	if err != nil {
+		t.Fatalf("error fetching key (%v)", err)
+	}
+	if string(resp.Kvs[0].Value) != "bar2" {
+		t.Fatalf("bad value. got %+v, expected 'bar2' value", resp)
+	}
+}