Add feature flag support

charts/ratify/templates/deployment.yaml

@@ -101,6 +101,10 @@ spec:
               valueFrom:
                 fieldRef:
                   fieldPath: metadata.namespace
+          {{- range $k, $v := .Values.featureFlags }}
+            - name: {{ $k }}
+              value: {{ $v | ternary 1 0 | quote }}
+          {{- end}}
           resources:
             {{- toYaml .Values.resources | nindent 12 }}
       volumes:

charts/ratify/values.yaml

@@ -103,3 +103,7 @@ crds:
     runAsGroup: 65532
     runAsNonRoot: true
     runAsUser: 65532
+
+# See https://github.com/deislabs/ratify/blob/main/docs/reference/usage.md for a list of available feature flags
+featureFlags:
+  # RATIFY_FEATURE_NAME: true

cmd/ratify/cmd/root.go

@@ -17,6 +17,7 @@ package cmd
 
 import (
 	"github.com/deislabs/ratify/pkg/common"
+	"github.com/deislabs/ratify/pkg/featureflag"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 )
@@ -30,6 +31,8 @@ var Root = New(use, shortDesc)
 
 func New(use, short string) *cobra.Command {
 	common.SetLoggingLevelFromEnv(logrus.StandardLogger())
+	featureflag.InitFeatureFlagsFromEnv()
+
 	root := &cobra.Command{
 		Use:   use,
 		Short: short,

docs/reference/usage.md

@@ -13,3 +13,8 @@ This page documents useful flags and options supported by Ratify
   - `DEBUG`
   - `TRACE`
 - `RATIFY_CONFIG`: change the default Ratify configuration directory. Defaults to `~/.ratify`
+
+## Feature flags
+
+Ratify may roll out new features behind feature flags, which are activated by setting the corresponding environment variable `RATIFY_<FEATURE_NAME>=1`.
+A value of `1` indicates the feature is active; any other value disables the flag.

pkg/featureflag/featureflag.go

@@ -0,0 +1,60 @@
+/*
+Copyright The Ratify 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 featureflag
+
+import (
+	"os"
+
+	"github.com/sirupsen/logrus"
+)
+
+// Feature flags are used to enable/disable experimental features.
+// They are activated via environment variables, starting with "RATIFY_", ex: RATIFY_DYNAMIC_PLUGINS=1
+// Remember to capture changes in the usage guide and release notes.
+var (
+	DynamicPlugins = new("DYNAMIC_PLUGINS", false)
+)
+
+var flags = make(map[string]*FeatureFlag)
+
+func InitFeatureFlagsFromEnv() {
+	for _, f := range flags {
+		value, ok := os.LookupEnv("RATIFY_" + f.Name)
+		if ok {
+			f.Enabled = value == "1"
+
+			if f.Enabled {
+				logrus.Infof("Feature flag %s is enabled", f.Name)
+			} else {
+				logrus.Infof("Feature flag %s is disabled", f.Name)
+			}
+		}
+	}
+}
+
+type FeatureFlag struct {
+	Name    string
+	Enabled bool
+}
+
+func new(name string, defaultValue bool) *FeatureFlag {
+	flag := &FeatureFlag{
+		Name: name,
+		Enabled: defaultValue,
+	}
+	flags[name] = flag
+	return flag
+}

pkg/featureflag/featureflag_test.go

@@ -0,0 +1,62 @@
+/*
+Copyright The Ratify 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 featureflag
+
+import (
+	"os"
+	"testing"
+)
+
+func TestFeatureFlag_UsesDefaultValues(t *testing.T) {
+	flag1 := new("TEST_FLAG1", false)
+	if flag1.Enabled {
+		t.Fatal("expected flag1 to be disabled")
+	}
+
+	flag2 := new("TEST_FLAG2", true)
+	if !flag2.Enabled {
+		t.Fatal("expected flag2 to be enabled")
+	}
+}
+
+func TestInitFeatureFlagsFromEnv_SetsValues(t *testing.T) {
+	flag1 := new("TEST_FLAG1", false)
+	flag2 := new("TEST_FLAG2", false)
+	flag3 := new("TEST_FLAG3", true)
+	flag4 := new("TEST_FLAG4", true)
+
+	// override flag defaults
+	os.Setenv("RATIFY_TEST_FLAG2", "1")
+	os.Setenv("RATIFY_TEST_FLAG4", "0")
+
+	InitFeatureFlagsFromEnv()
+
+	if flag1.Enabled {
+		t.Fatal("expected flag1 to be disabled")
+	}
+
+	if !flag2.Enabled {
+		t.Fatal("expected flag2 to be enabled")
+	}
+
+	if !flag3.Enabled {
+		t.Fatal("expected flag3 to be enabled")
+	}
+
+	if flag4.Enabled {
+		t.Fatal("expected flag4 to be disabled")
+	}
+}