failed on unregistered featuregate (open-telemetry#5660)

* failed on unregistered featuregate
* add test for existing/noexisting gates
* change command to use Apply for now

Signed-off-by: Ziqi Zhao <[email protected]>

CHANGELOG.md

@@ -32,6 +32,7 @@
   - `component.WithTracesProcessor` -> `component.WithTracesProcessorAndStabilityLevel`
   - `component.WithMetricsProcessor` -> `component.WithMetricsProcessorAndStabilityLevel`
   - `component.WithLogsProcessor` -> `component.WithLogsProcessorAndStabilityLevel`
+- Deprecate `Registry.Apply` in `service.featuregate` (#5660)
 
 ### 💡 Enhancements 💡
 

service/featuregate/gates.go

@@ -46,6 +46,7 @@ type Registry struct {
 
 // Apply a configuration in the form of a map of Gate identifiers to boolean values.
 // Sets only those values provided in the map, other gate values are not changed.
+// Deprecated: [v0.56.0] Use MustApply instead.
 func (r *Registry) Apply(cfg map[string]bool) {
 	r.mu.Lock()
 	defer r.mu.Unlock()
@@ -57,6 +58,21 @@ func (r *Registry) Apply(cfg map[string]bool) {
 	}
 }
 
+// MustApply a configuration in the form of a map of Gate identifiers to boolean values.
+// Sets only those values provided in the map, other gate values are not changed.
+func (r *Registry) MustApply(cfg map[string]bool) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	for id, val := range cfg {
+		if g, ok := r.gates[id]; ok {
+			g.Enabled = val
+			r.gates[g.ID] = g
+		} else {
+			panic(fmt.Sprintf("feature gate %s is unregistered", id))
+		}
+	}
+}
+
 // IsEnabled returns true if a registered feature gate is enabled and false otherwise.
 func (r *Registry) IsEnabled(id string) bool {
 	r.mu.RLock()

service/featuregate/gates_test.go

@@ -44,3 +44,47 @@ func TestRegistry(t *testing.T) {
 		r.MustRegister(gate)
 	})
 }
+
+func TestRegistryWithMustApply(t *testing.T) {
+	r := Registry{gates: map[string]Gate{}}
+	gate := Gate{
+		ID:          "foo",
+		Description: "Test Gate",
+		Enabled:     true,
+	}
+	assert.NoError(t, r.Register(gate))
+
+	tests := []struct {
+		name        string
+		gate        string
+		enabled     bool
+		shouldError bool
+	}{
+		{
+			name:        "existing_gate",
+			gate:        "foo",
+			enabled:     false,
+			shouldError: false,
+		},
+		{
+			name:        "none_existing_gate",
+			gate:        "bar",
+			enabled:     false,
+			shouldError: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.shouldError {
+				assert.Panics(t, func() {
+					r.MustApply(map[string]bool{tt.gate: tt.enabled})
+				})
+			} else {
+				r.MustApply(map[string]bool{tt.gate: tt.enabled})
+				assert.Equal(t, tt.enabled, r.IsEnabled(tt.gate))
+			}
+
+		})
+	}
+}