make patch handle conflicts gracefully

pkg/apiserver/resthandler.go

@@ -17,10 +17,12 @@ limitations under the License.
 package apiserver
 
 import (
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"net/url"
 	gpath "path"
+	"reflect"
 	"strings"
 	"time"
 
@@ -83,6 +85,9 @@ type RequestScope struct {
 // may be used to deserialize an options object to pass to the getter.
 type getterFunc func(ctx api.Context, name string, req *restful.Request) (runtime.Object, error)
 
+// MaxPatchConflicts is the maximum number of conflicts retry for during a patch operation before returning failure
+const MaxPatchConflicts = 5
+
 // getResourceHandler is an HTTP handler function for get requests. It delegates to the
 // passed-in getterFunc to perform the actual get.
 func getResourceHandler(scope RequestScope, getter getterFunc) restful.RouteFunction {
@@ -392,49 +397,26 @@ func PatchResource(r rest.Patcher, scope RequestScope, typer runtime.ObjectTyper
 			}
 		}
 
-		versionedObj, err := converter.ConvertToVersion(obj, scope.APIVersion)
+		versionedObj, err := converter.ConvertToVersion(r.New(), scope.APIVersion)
 		if err != nil {
 			errorJSON(err, scope.Codec, w)
 			return
 		}
 
-		original, err := r.Get(ctx, name)
-		if err != nil {
-			errorJSON(err, scope.Codec, w)
-			return
+		contentType := req.HeaderParameter("Content-Type")
+		// Remove "; charset=" if included in header.
+		if idx := strings.Index(contentType, ";"); idx > 0 {
+			contentType = contentType[:idx]
 		}
+		patchType := api.PatchType(contentType)
 
-		originalObjJS, err := scope.Codec.Encode(original)
-		if err != nil {
-			errorJSON(err, scope.Codec, w)
-			return
-		}
 		patchJS, err := readBody(req.Request)
 		if err != nil {
 			errorJSON(err, scope.Codec, w)
 			return
 		}
-		contentType := req.HeaderParameter("Content-Type")
-		patchedObjJS, err := getPatchedJS(contentType, originalObjJS, patchJS, versionedObj)
-		if err != nil {
-			errorJSON(err, scope.Codec, w)
-			return
-		}
 
-		if err := scope.Codec.DecodeInto(patchedObjJS, obj); err != nil {
-			errorJSON(err, scope.Codec, w)
-			return
-		}
-		if err := checkName(obj, name, namespace, scope.Namer); err != nil {
-			errorJSON(err, scope.Codec, w)
-			return
-		}
-
-		result, err := finishRequest(timeout, func() (runtime.Object, error) {
-			// update should never create as previous get would fail
-			obj, _, err := r.Update(ctx, obj)
-			return obj, err
-		})
+		result, err := patchResource(ctx, timeout, versionedObj, r, name, patchType, patchJS, scope.Namer, scope.Codec)
 		if err != nil {
 			errorJSON(err, scope.Codec, w)
 			return
@@ -447,6 +429,130 @@ func PatchResource(r rest.Patcher, scope RequestScope, typer runtime.ObjectTyper
 
 		write(http.StatusOK, scope.APIVersion, scope.Codec, result, w, req.Request)
 	}
+
+}
+
+// patchResource divides PatchResource for easier unit testing
+func patchResource(ctx api.Context, timeout time.Duration, versionedObj runtime.Object, patcher rest.Patcher, name string, patchType api.PatchType, patchJS []byte, namer ScopeNamer, codec runtime.Codec) (runtime.Object, error) {
+	namespace := api.NamespaceValue(ctx)
+
+	original, err := patcher.Get(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+
+	originalObjJS, err := codec.Encode(original)
+	if err != nil {
+		return nil, err
+	}
+	originalPatchedObjJS, err := getPatchedJS(patchType, originalObjJS, patchJS, versionedObj)
+	if err != nil {
+		return nil, err
+	}
+
+	objToUpdate := patcher.New()
+	if err := codec.DecodeInto(originalPatchedObjJS, objToUpdate); err != nil {
+		return nil, err
+	}
+	if err := checkName(objToUpdate, name, namespace, namer); err != nil {
+		return nil, err
+	}
+
+	return finishRequest(timeout, func() (runtime.Object, error) {
+		// update should never create as previous get would fail
+		updateObject, _, updateErr := patcher.Update(ctx, objToUpdate)
+		for i := 0; i < MaxPatchConflicts && (errors.IsConflict(updateErr)); i++ {
+
+			// on a conflict,
+			// 1. build a strategic merge patch from originalJS and the patchedJS.  Different patch types can
+			//    be specified, but a strategic merge patch should be expressive enough handle them.  Build the
+			//    patch with this type to handle those cases.
+			// 2. build a strategic merge patch from originalJS and the currentJS
+			// 3. ensure no conflicts between the two patches
+			// 4. apply the #1 patch to the currentJS object
+			// 5. retry the update
+			currentObject, err := patcher.Get(ctx, name)
+			if err != nil {
+				return nil, err
+			}
+			currentObjectJS, err := codec.Encode(currentObject)
+			if err != nil {
+				return nil, err
+			}
+
+			currentPatch, err := strategicpatch.CreateStrategicMergePatch(originalObjJS, currentObjectJS, patcher.New())
+			if err != nil {
+				return nil, err
+			}
+			originalPatch, err := strategicpatch.CreateStrategicMergePatch(originalObjJS, originalPatchedObjJS, patcher.New())
+			if err != nil {
+				return nil, err
+			}
+
+			diff1 := make(map[string]interface{})
+			if err := json.Unmarshal(originalPatch, &diff1); err != nil {
+				return nil, err
+			}
+			diff2 := make(map[string]interface{})
+			if err := json.Unmarshal(currentPatch, &diff2); err != nil {
+				return nil, err
+			}
+			if hasConflicts(diff1, diff2) {
+				return updateObject, updateErr
+			}
+
+			newlyPatchedObjJS, err := getPatchedJS(api.StrategicMergePatchType, currentObjectJS, originalPatch, versionedObj)
+			if err != nil {
+				return nil, err
+			}
+			if err := codec.DecodeInto(newlyPatchedObjJS, objToUpdate); err != nil {
+				return nil, err
+			}
+
+			updateObject, _, updateErr = patcher.Update(ctx, objToUpdate)
+		}
+
+		return updateObject, updateErr
+	})
+}
+
+// hasConflicts returns true if the left and right JSON interface objects overlap with
+// different values in any key.  The code will panic if an unrecognized type is passed
+// (anything not returned by a JSON decode).  All keys are required to be strings.
+func hasConflicts(left, right interface{}) bool {
+	switch typedLeft := left.(type) {
+	case map[string]interface{}:
+		switch typedRight := right.(type) {
+		case map[string]interface{}:
+			for key, leftValue := range typedLeft {
+				if rightValue, ok := typedRight[key]; ok && hasConflicts(leftValue, rightValue) {
+					return true
+				}
+			}
+			return false
+		default:
+			return true
+		}
+	case []interface{}:
+		switch typedRight := right.(type) {
+		case []interface{}:
+			if len(typedLeft) != len(typedRight) {
+				return true
+			}
+			for i := range typedLeft {
+				if hasConflicts(typedLeft[i], typedRight[i]) {
+					return true
+				}
+			}
+			return false
+		default:
+			return true
+		}
+	case string, float64, bool, int, int64, nil:
+		return !reflect.DeepEqual(left, right)
+	default:
+		panic(fmt.Sprintf("unknown type: %v", reflect.TypeOf(left)))
+	}
 }
 
 // UpdateResource returns a function that will handle a resource update
@@ -736,12 +842,7 @@ func setListSelfLink(obj runtime.Object, req *restful.Request, namer ScopeNamer)
 
 }
 
-func getPatchedJS(contentType string, originalJS, patchJS []byte, obj runtime.Object) ([]byte, error) {
-	// Remove "; charset=" if included in header.
-	if idx := strings.Index(contentType, ";"); idx > 0 {
-		contentType = contentType[:idx]
-	}
-	patchType := api.PatchType(contentType)
+func getPatchedJS(patchType api.PatchType, originalJS, patchJS []byte, obj runtime.Object) ([]byte, error) {
 	switch patchType {
 	case api.JSONPatchType:
 		patchObj, err := jsonpatch.DecodePatch(patchJS)
@@ -755,6 +856,6 @@ func getPatchedJS(contentType string, originalJS, patchJS []byte, obj runtime.Ob
 		return strategicpatch.StrategicMergePatchData(originalJS, patchJS, obj)
 	default:
 		// only here as a safety net - go-restful filters content-type
-		return nil, fmt.Errorf("unknown Content-Type header for patch: %s", contentType)
+		return nil, fmt.Errorf("unknown Content-Type header for patch: %v", patchType)
 	}
 }

pkg/apiserver/resthandler_test.go

@@ -17,10 +17,22 @@ limitations under the License.
 package apiserver
 
 import (
+	"errors"
+	"fmt"
+	"reflect"
 	"testing"
+	"time"
+
+	"github.com/emicklei/go-restful"
+	"github.com/evanphx/json-patch"
 
 	"k8s.io/kubernetes/pkg/api"
+	apierrors "k8s.io/kubernetes/pkg/api/errors"
+	"k8s.io/kubernetes/pkg/api/latest"
 	"k8s.io/kubernetes/pkg/api/unversioned"
+	"k8s.io/kubernetes/pkg/runtime"
+	"k8s.io/kubernetes/pkg/util"
+	"k8s.io/kubernetes/pkg/util/strategicpatch"
 )
 
 type testPatchType struct {
@@ -40,12 +52,280 @@ func TestPatchAnonymousField(t *testing.T) {
 	patch := `{"theField": "changed!"}`
 	expectedJS := `{"kind":"testPatchType","theField":"changed!"}`
 
-	actualBytes, err := getPatchedJS(string(api.StrategicMergePatchType), []byte(originalJS), []byte(patch), &testPatchType{})
+	actualBytes, err := getPatchedJS(api.StrategicMergePatchType, []byte(originalJS), []byte(patch), &testPatchType{})
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
 	if string(actualBytes) != expectedJS {
 		t.Errorf("expected %v, got %v", expectedJS, string(actualBytes))
 	}
+}
+
+type testPatcher struct {
+	// startingPod is used for the first Get
+	startingPod *api.Pod
+
+	// updatePod is the pod that is used for conflict comparison and returned for the SECOND Get
+	updatePod *api.Pod
+
+	numGets int
+}
+
+func (p *testPatcher) New() runtime.Object {
+	return &api.Pod{}
+}
+
+func (p *testPatcher) Update(ctx api.Context, obj runtime.Object) (runtime.Object, bool, error) {
+	inPod := obj.(*api.Pod)
+	if inPod.ResourceVersion != p.updatePod.ResourceVersion {
+		return nil, false, apierrors.NewConflict("Pod", inPod.Name, fmt.Errorf("existing %v, new %v", p.updatePod.ResourceVersion, inPod.ResourceVersion))
+	}
+
+	return inPod, false, nil
+}
+
+func (p *testPatcher) Get(ctx api.Context, name string) (runtime.Object, error) {
+	if p.numGets > 0 {
+		return p.updatePod, nil
+	}
+	p.numGets++
+
+	return p.startingPod, nil
+}
+
+type testNamer struct {
+	namespace string
+	name      string
+}
+
+func (p *testNamer) Namespace(req *restful.Request) (namespace string, err error) {
+	return p.namespace, nil
+}
+
+// Name returns the name from the request, and an optional namespace value if this is a namespace
+// scoped call. An error is returned if the name is not available.
+func (p *testNamer) Name(req *restful.Request) (namespace, name string, err error) {
+	return p.namespace, p.name, nil
+}
+
+// ObjectName returns the namespace and name from an object if they exist, or an error if the object
+// does not support names.
+func (p *testNamer) ObjectName(obj runtime.Object) (namespace, name string, err error) {
+	return p.namespace, p.name, nil
+}
+
+// SetSelfLink sets the provided URL onto the object. The method should return nil if the object
+// does not support selfLinks.
+func (p *testNamer) SetSelfLink(obj runtime.Object, url string) error {
+	return errors.New("not implemented")
+}
+
+// GenerateLink creates a path and query for a given runtime object that represents the canonical path.
+func (p *testNamer) GenerateLink(req *restful.Request, obj runtime.Object) (path, query string, err error) {
+	return "", "", errors.New("not implemented")
+}
+
+// GenerateLink creates a path and query for a list that represents the canonical path.
+func (p *testNamer) GenerateListLink(req *restful.Request) (path, query string, err error) {
+	return "", "", errors.New("not implemented")
+}
+
+type patchTestCase struct {
+	name string
+
+	// startingPod is used for the first Get
+	startingPod *api.Pod
+	// changedPod is the "destination" pod for the patch.  The test will create a patch from the startingPod to the changedPod
+	// to use when calling the patch operation
+	changedPod *api.Pod
+	// updatePod is the pod that is used for conflict comparison and returned for the SECOND Get
+	updatePod *api.Pod
+
+	// expectedPod is the pod that you expect to get back after the patch is complete
+	expectedPod   *api.Pod
+	expectedError string
+}
+
+func (tc *patchTestCase) Run(t *testing.T) {
+	t.Logf("Starting test %s", tc.name)
+
+	namespace := tc.startingPod.Namespace
+	name := tc.startingPod.Name
+
+	codec := latest.GroupOrDie("").Codec
+
+	testPatcher := &testPatcher{}
+	testPatcher.startingPod = tc.startingPod
+	testPatcher.updatePod = tc.updatePod
+
+	ctx := api.NewDefaultContext()
+	ctx = api.WithNamespace(ctx, namespace)
+
+	namer := &testNamer{namespace, name}
+
+	versionedObj, err := api.Scheme.ConvertToVersion(&api.Pod{}, "v1")
+	if err != nil {
+		t.Errorf("%s: unexpected error: %v", tc.name, err)
+		return
+	}
+
+	for _, patchType := range []api.PatchType{api.JSONPatchType, api.MergePatchType, api.StrategicMergePatchType} {
+		// TODO SUPPORT THIS!
+		if patchType == api.JSONPatchType {
+			continue
+		}
+		t.Logf("Working with patchType %v", patchType)
+
+		originalObjJS, err := codec.Encode(tc.startingPod)
+		if err != nil {
+			t.Errorf("%s: unexpected error: %v", tc.name, err)
+			return
+		}
+		changedJS, err := codec.Encode(tc.changedPod)
+		if err != nil {
+			t.Errorf("%s: unexpected error: %v", tc.name, err)
+			return
+		}
+
+		patch := []byte{}
+		switch patchType {
+		case api.JSONPatchType:
+			continue
+
+		case api.StrategicMergePatchType:
+			patch, err = strategicpatch.CreateStrategicMergePatch(originalObjJS, changedJS, &api.Pod{})
+			if err != nil {
+				t.Errorf("%s: unexpected error: %v", tc.name, err)
+				return
+			}
+
+		case api.MergePatchType:
+			patch, err = jsonpatch.CreateMergePatch(originalObjJS, changedJS)
+			if err != nil {
+				t.Errorf("%s: unexpected error: %v", tc.name, err)
+				return
+			}
+
+		}
+
+		resultObj, err := patchResource(ctx, 1*time.Second, versionedObj, testPatcher, name, patchType, patch, namer, codec)
+		if len(tc.expectedError) != 0 {
+			if err == nil || err.Error() != tc.expectedError {
+				t.Errorf("%s: expected error %v, but got %v", tc.name, tc.expectedError, err)
+				return
+			}
+		} else {
+			if err != nil {
+				t.Errorf("%s: unexpected error: %v", tc.name, err)
+				return
+			}
+		}
+
+		if tc.expectedPod == nil {
+			if resultObj != nil {
+				t.Errorf("%s: unexpected result: %v", tc.name, resultObj)
+			}
+			return
+		}
+
+		resultPod := resultObj.(*api.Pod)
+
+		// roundtrip to get defaulting
+		expectedJS, err := codec.Encode(tc.expectedPod)
+		if err != nil {
+			t.Errorf("%s: unexpected error: %v", tc.name, err)
+			return
+		}
+		expectedObj, err := codec.Decode(expectedJS)
+		if err != nil {
+			t.Errorf("%s: unexpected error: %v", tc.name, err)
+			return
+		}
+		reallyExpectedPod := expectedObj.(*api.Pod)
+
+		if !reflect.DeepEqual(*reallyExpectedPod, *resultPod) {
+			t.Errorf("%s mismatch: %v\n", tc.name, util.ObjectGoPrintDiff(reallyExpectedPod, resultPod))
+			return
+		}
+	}
 
 }
+
+func TestPatchResourceWithVersionConflict(t *testing.T) {
+	namespace := "bar"
+	name := "foo"
+	fifteen := int64(15)
+	thirty := int64(30)
+
+	tc := &patchTestCase{
+		name: "TestPatchResourceWithVersionConflict",
+
+		startingPod: &api.Pod{},
+		changedPod:  &api.Pod{},
+		updatePod:   &api.Pod{},
+
+		expectedPod: &api.Pod{},
+	}
+
+	tc.startingPod.Name = name
+	tc.startingPod.Namespace = namespace
+	tc.startingPod.ResourceVersion = "1"
+	tc.startingPod.APIVersion = "v1"
+	tc.startingPod.Spec.ActiveDeadlineSeconds = &fifteen
+
+	tc.changedPod.Name = name
+	tc.changedPod.Namespace = namespace
+	tc.changedPod.ResourceVersion = "1"
+	tc.changedPod.APIVersion = "v1"
+	tc.changedPod.Spec.ActiveDeadlineSeconds = &thirty
+
+	tc.updatePod.Name = name
+	tc.updatePod.Namespace = namespace
+	tc.updatePod.ResourceVersion = "2"
+	tc.updatePod.APIVersion = "v1"
+	tc.updatePod.Spec.ActiveDeadlineSeconds = &fifteen
+	tc.updatePod.Spec.NodeName = "anywhere"
+
+	tc.expectedPod.Name = name
+	tc.expectedPod.Namespace = namespace
+	tc.expectedPod.ResourceVersion = "2"
+	tc.expectedPod.Spec.ActiveDeadlineSeconds = &thirty
+	tc.expectedPod.Spec.NodeName = "anywhere"
+
+	tc.Run(t)
+}
+
+func TestPatchResourceWithConflict(t *testing.T) {
+	namespace := "bar"
+	name := "foo"
+
+	tc := &patchTestCase{
+		name: "TestPatchResourceWithConflict",
+
+		startingPod: &api.Pod{},
+		changedPod:  &api.Pod{},
+		updatePod:   &api.Pod{},
+
+		expectedError: `Pod "foo" cannot be updated: existing 2, new 1`,
+	}
+
+	tc.startingPod.Name = name
+	tc.startingPod.Namespace = namespace
+	tc.startingPod.ResourceVersion = "1"
+	tc.startingPod.APIVersion = "v1"
+	tc.startingPod.Spec.NodeName = "here"
+
+	tc.changedPod.Name = name
+	tc.changedPod.Namespace = namespace
+	tc.changedPod.ResourceVersion = "1"
+	tc.changedPod.APIVersion = "v1"
+	tc.changedPod.Spec.NodeName = "there"
+
+	tc.updatePod.Name = name
+	tc.updatePod.Namespace = namespace
+	tc.updatePod.ResourceVersion = "2"
+	tc.updatePod.APIVersion = "v1"
+	tc.updatePod.Spec.NodeName = "anywhere"
+
+	tc.Run(t)
+}