From 7b6554fd3030a21631bb23e1827f4af1d9b93a4f Mon Sep 17 00:00:00 2001
From: Chao Chen <chaochn@amazon.com>
Date: Fri, 22 Oct 2021 16:36:37 -0700
Subject: [PATCH 1/2] non mutating requests pass through quotaKVServer when
 NOSPACE

---
 server/storage/quota.go            |  7 ++++++-
 tests/integration/v3_alarm_test.go | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/server/storage/quota.go b/server/storage/quota.go
index e15079d45..46b350653 100644
--- a/server/storage/quota.go
+++ b/server/storage/quota.go
@@ -127,8 +127,13 @@ func NewBackendQuota(cfg config.ServerConfig, be backend.Backend, name string) Q
 }
 
 func (b *BackendQuota) Available(v interface{}) bool {
+	cost := b.Cost(v)
+	// if there are no mutating requests, it's safe to pass through
+	if cost == 0 {
+		return true
+	}
 	// TODO: maybe optimize Backend.Size()
-	return b.be.Size()+int64(b.Cost(v)) < b.maxBackendBytes
+	return b.be.Size()+int64(cost) < b.maxBackendBytes
 }
 
 func (b *BackendQuota) Cost(v interface{}) int {
diff --git a/tests/integration/v3_alarm_test.go b/tests/integration/v3_alarm_test.go
index 929d9b926..2fce27bf8 100644
--- a/tests/integration/v3_alarm_test.go
+++ b/tests/integration/v3_alarm_test.go
@@ -88,6 +88,30 @@ func TestV3StorageQuotaApply(t *testing.T) {
 		}
 	}
 
+	// txn with non-mutating Ops should go through when NOSPACE alarm is raised
+	_, err = kvc0.Txn(context.TODO(), &pb.TxnRequest{
+		Compare: []*pb.Compare{
+			{
+				Key:         key,
+				Result:      pb.Compare_EQUAL,
+				Target:      pb.Compare_CREATE,
+				TargetUnion: &pb.Compare_CreateRevision{CreateRevision: 0},
+			},
+		},
+		Success: []*pb.RequestOp{
+			{
+				Request: &pb.RequestOp_RequestDeleteRange{
+					RequestDeleteRange: &pb.DeleteRangeRequest{
+						Key: key,
+					},
+				},
+			},
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
 	ctx, cancel := context.WithTimeout(context.TODO(), integration.RequestWaitTimeout)
 	defer cancel()
 

From 9c6d57918dab6b8cda8824d0eb5ee8f8c75ad958 Mon Sep 17 00:00:00 2001
From: Chao Chen <chaochn@amazon.com>
Date: Fri, 22 Oct 2021 16:36:59 -0700
Subject: [PATCH 2/2] update CHANGELOG

---
 CHANGELOG-3.5.md | 4 ----
 CHANGELOG-3.6.md | 5 +++++
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG-3.5.md b/CHANGELOG-3.5.md
index eac0888c7..78015a501 100644
--- a/CHANGELOG-3.5.md
+++ b/CHANGELOG-3.5.md
@@ -25,10 +25,6 @@ See [code changes](https://github.com/etcd-io/etcd/compare/v3.5.0...v3.5.1) and
 
 - Endpoints self identify now as `etcd-endpoints://{id}/{authority}` where authority is based on first endpoint passed, for example `etcd-endpoints://0xc0009d8540/localhost:2079`
 
-### tools/benchmark
-
-- [Add etcd client autoSync flag](https://github.com/etcd-io/etcd/pull/13416)
-
 ### Other
 
 - Updated [base image](https://github.com/etcd-io/etcd/pull/13386) from `debian:buster-v1.4.0` to `debian:bullseye-20210927` to fix the following critical CVEs:
diff --git a/CHANGELOG-3.6.md b/CHANGELOG-3.6.md
index 73fdd8584..f792d3a13 100644
--- a/CHANGELOG-3.6.md
+++ b/CHANGELOG-3.6.md
@@ -32,6 +32,11 @@ See [code changes](https://github.com/etcd-io/etcd/compare/v3.5.0...v3.6.0).
 ### etcd server
 
 - Add [`etcd --log-format`](https://github.com/etcd-io/etcd/pull/13339) flag to support log format.
+- Fix [non mutating requests pass through quotaKVServer when NOSPACE](https://github.com/etcd-io/etcd/pull/13435)
+
+### tools/benchmark
+
+- [Add etcd client autoSync flag](https://github.com/etcd-io/etcd/pull/13416)
 
 ### Metrics, Monitoring