Disallow -v2-deprecation>'not-yet' combined with --enable-v2

server/config/config.go

@@ -192,6 +192,9 @@ type ServerConfig struct {
 	// ExperimentalBootstrapDefragThresholdMegabytes is the minimum number of megabytes needed to be freed for etcd server to
 	// consider running defrag during bootstrap. Needs to be set to non-zero value to take effect.
 	ExperimentalBootstrapDefragThresholdMegabytes uint `json:"experimental-bootstrap-defrag-threshold-megabytes"`
+
+	// V2Deprecation defines a phase of v2store deprecation process.
+	V2Deprecation V2DeprecationEnum `json:"v2-deprecation"`
 }
 
 // VerifyBootstrap sanity-checks the initial config for bootstrap case

server/config/v2_deprecation.go

@@ -0,0 +1,50 @@
+// Copyright 2021 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package config
+
+type V2DeprecationEnum string
+
+const (
+	// Default in v3.5.  Issues a warning if v2store have meaningful content.
+	V2_DEPR_0_NOT_YET = V2DeprecationEnum("not-yet")
+	// Default in v3.6.  Meaningful v2 state is not allowed.
+	// The V2 files are maintained for v3.5 rollback.
+	V2_DEPR_1_WRITE_ONLY = V2DeprecationEnum("write-only")
+	// V2store is WIPED if found !!!
+	V2_DEPR_1_WRITE_ONLY_DROP = V2DeprecationEnum("write-only-drop-data")
+	// V2store is neither written nor read. Usage of this configuration is blocking
+	// ability to rollback to etcd v3.5.
+	V2_DEPR_2_GONE = V2DeprecationEnum("gone")
+
+	V2_DEPR_DEFAULT = V2_DEPR_0_NOT_YET
+)
+
+func (e V2DeprecationEnum) IsAtLeast(v2d V2DeprecationEnum) bool {
+	return e.level() >= v2d.level()
+}
+
+func (e V2DeprecationEnum) level() int {
+	switch e {
+	case V2_DEPR_0_NOT_YET:
+		return 0
+	case V2_DEPR_1_WRITE_ONLY:
+		return 1
+	case V2_DEPR_1_WRITE_ONLY_DROP:
+		return 2
+	case V2_DEPR_2_GONE:
+		return 3
+	}
+	panic("Unknown V2DeprecationEnum: " + e)
+}

server/config/v2_deprecation_test.go

@@ -0,0 +1,41 @@
+// Copyright 2021 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package config
+
+import "testing"
+
+func TestV2DeprecationEnum_IsAtLeast(t *testing.T) {
+	tests := []struct {
+		e    V2DeprecationEnum
+		v2d  V2DeprecationEnum
+		want bool
+	}{
+		{V2_DEPR_0_NOT_YET, V2_DEPR_0_NOT_YET, true},
+		{V2_DEPR_0_NOT_YET, V2_DEPR_1_WRITE_ONLY_DROP, false},
+		{V2_DEPR_0_NOT_YET, V2_DEPR_2_GONE, false},
+		{V2_DEPR_2_GONE, V2_DEPR_1_WRITE_ONLY_DROP, true},
+		{V2_DEPR_2_GONE, V2_DEPR_0_NOT_YET, true},
+		{V2_DEPR_2_GONE, V2_DEPR_2_GONE, true},
+		{V2_DEPR_1_WRITE_ONLY, V2_DEPR_1_WRITE_ONLY_DROP, false},
+		{V2_DEPR_1_WRITE_ONLY_DROP, V2_DEPR_1_WRITE_ONLY, true},
+	}
+	for _, tt := range tests {
+		t.Run(string(tt.e)+" >= "+string(tt.v2d), func(t *testing.T) {
+			if got := tt.e.IsAtLeast(tt.v2d); got != tt.want {
+				t.Errorf("IsAtLeast() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}