Merge pull request #43152 from ncdc/watch-cache-retry-live-object-on-conflict

Automatic merge from submit-queue (batch tested with PRs 52176, 43152). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>..

etcd3 store: retry with live object on conflict if there was a suggestion

Retry with a live object instead of the cached version if the watch
cache receives a conflict trying to do the update.

Fixes #41892

staging/src/k8s.io/apiserver/pkg/storage/etcd3/BUILD

@@ -19,6 +19,7 @@ go_test(
         "//vendor/github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes:go_default_library",
         "//vendor/github.com/coreos/etcd/integration:go_default_library",
         "//vendor/golang.org/x/net/context:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/api/errors:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/api/testing:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/fields:go_default_library",

staging/src/k8s.io/apiserver/pkg/storage/etcd3/store.go

@@ -32,6 +32,7 @@ import (
 	"github.com/golang/glog"
 	"golang.org/x/net/context"
 
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/api/meta"
 	"k8s.io/apimachinery/pkg/conversion"
 	"k8s.io/apimachinery/pkg/runtime"
@@ -271,6 +272,14 @@ func (s *store) GuaranteedUpdate(
 	}
 	key = path.Join(s.pathPrefix, key)
 
+	getCurrentState := func() (*objState, error) {
+		getResp, err := s.client.KV.Get(ctx, key, s.getOps...)
+		if err != nil {
+			return nil, err
+		}
+		return s.getState(getResp, key, v, ignoreNotFound)
+	}
+
 	var origState *objState
 	var mustCheckData bool
 	if len(suggestion) == 1 && suggestion[0] != nil {
@@ -280,11 +289,7 @@ func (s *store) GuaranteedUpdate(
 		}
 		mustCheckData = true
 	} else {
-		getResp, err := s.client.KV.Get(ctx, key, s.getOps...)
-		if err != nil {
-			return err
-		}
-		origState, err = s.getState(getResp, key, v, ignoreNotFound)
+		origState, err = getCurrentState()
 		if err != nil {
 			return err
 		}
@@ -299,6 +304,18 @@ func (s *store) GuaranteedUpdate(
 
 		ret, ttl, err := s.updateState(origState, tryUpdate)
 		if err != nil {
+			// It's possible we were working with stale data
+			if mustCheckData && apierrors.IsConflict(err) {
+				// Actually fetch
+				origState, err = getCurrentState()
+				if err != nil {
+					return err
+				}
+				mustCheckData = false
+				// Retry
+				continue
+			}
+
 			return err
 		}
 
@@ -311,11 +328,7 @@ func (s *store) GuaranteedUpdate(
 			// etcd in order to be sure the data in the store is equivalent to
 			// our desired serialization
 			if mustCheckData {
-				getResp, err := s.client.KV.Get(ctx, key, s.getOps...)
-				if err != nil {
-					return err
-				}
-				origState, err = s.getState(getResp, key, v, ignoreNotFound)
+				origState, err = getCurrentState()
 				if err != nil {
 					return err
 				}

staging/src/k8s.io/apiserver/pkg/storage/etcd3/store_test.go

@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"encoding/base64"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"reflect"
 	"strconv"
@@ -29,6 +30,7 @@ import (
 	"github.com/coreos/etcd/clientv3"
 	"github.com/coreos/etcd/integration"
 	"golang.org/x/net/context"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	apitesting "k8s.io/apimachinery/pkg/api/testing"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/fields"
@@ -584,6 +586,53 @@ func TestGuaranteedUpdateWithConflict(t *testing.T) {
 	}
 }
 
+func TestGuaranteedUpdateWithSuggestionAndConflict(t *testing.T) {
+	ctx, store, cluster := testSetup(t)
+	defer cluster.Terminate(t)
+	key, originalPod := testPropogateStore(ctx, t, store, &example.Pod{ObjectMeta: metav1.ObjectMeta{Name: "foo"}})
+
+	// First, update without a suggestion so originalPod is outdated
+	updatedPod := &example.Pod{}
+	err := store.GuaranteedUpdate(ctx, key, updatedPod, false, nil,
+		storage.SimpleUpdate(func(obj runtime.Object) (runtime.Object, error) {
+			pod := obj.(*example.Pod)
+			pod.Name = "foo-2"
+			return pod, nil
+		}),
+	)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	// Second, update using the outdated originalPod as the suggestion. Return a conflict error when
+	// passed originalPod, and make sure that SimpleUpdate is called a second time after a live lookup
+	// with the value of updatedPod.
+	sawConflict := false
+	updatedPod2 := &example.Pod{}
+	err = store.GuaranteedUpdate(ctx, key, updatedPod2, false, nil,
+		storage.SimpleUpdate(func(obj runtime.Object) (runtime.Object, error) {
+			pod := obj.(*example.Pod)
+			if pod.Name != "foo-2" {
+				if sawConflict {
+					t.Fatalf("unexpected second conflict")
+				}
+				sawConflict = true
+				// simulated stale object - return a conflict
+				return nil, apierrors.NewConflict(example.SchemeGroupVersion.WithResource("pods").GroupResource(), "name", errors.New("foo"))
+			}
+			pod.Name = "foo-3"
+			return pod, nil
+		}),
+		originalPod,
+	)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if updatedPod2.Name != "foo-3" {
+		t.Errorf("unexpected pod name: %q", updatedPod2.Name)
+	}
+}
+
 func TestTransformationFailure(t *testing.T) {
 	codec := apitesting.TestCodec(codecs, examplev1.SchemeGroupVersion)
 	cluster := integration.NewClusterV3(t, &integration.ClusterConfig{Size: 1})