add unreliable bus test utility (#69)

testutils/unreliablebus.go

@@ -0,0 +1,61 @@
+// Copyright 2023 LiveKit, Inc.
+//
+// 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 testutils
+
+import (
+	"context"
+	"math/rand"
+
+	"go.uber.org/atomic"
+)
+
+type AtomicFailureRate struct {
+	v *atomic.Float64
+}
+
+func NewAtomicFailureRate(v float64) AtomicFailureRate {
+	return AtomicFailureRate{v: atomic.NewFloat64(v)}
+}
+
+func (g *AtomicFailureRate) Rate() float64 {
+	return g.v.Load()
+}
+
+func (g *AtomicFailureRate) SetRate(v float64) {
+	g.v.Store(v)
+}
+
+func WithUnreliableBus(rate AtomicFailureRate) TestBusOption {
+	return WithUnreliableBusChannel(rate, "")
+}
+
+func WithUnreliableBusChannel(rate AtomicFailureRate, channelFilter string) TestBusOption {
+	return WithSubscribeInterceptor(func(_ context.Context, channel string, next ReadHandler) ReadHandler {
+		if channelFilter != "" && channelFilter != channel {
+			return next
+		}
+
+		rng := rand.New(rand.NewSource(0))
+		return func() ([]byte, bool) {
+			for {
+				b, ok := next()
+				if ok && rate.Rate() > rng.Float64() {
+					continue
+				}
+				return b, ok
+			}
+		}
+	})
+}