Add cloud_pubsub input plugin (#5136)

plugins/inputs/cloud_pubsub/subscription_stub.go

@@ -0,0 +1,104 @@
+package cloud_pubsub
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+type stubSub struct {
+	id       string
+	messages chan *testMsg
+}
+
+func (s *stubSub) ID() string {
+	return s.id
+}
+
+func (s *stubSub) Receive(ctx context.Context, f func(context.Context, message)) error {
+	for {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case m := <-s.messages:
+			f(ctx, m)
+		}
+	}
+}
+
+type testMsg struct {
+	id          string
+	value       string
+	attributes  map[string]string
+	publishTime time.Time
+
+	tracker *testTracker
+}
+
+func (tm *testMsg) Ack() {
+	tm.tracker.Ack()
+}
+
+func (tm *testMsg) Nack() {
+	tm.tracker.Nack()
+}
+
+func (tm *testMsg) ID() string {
+	return tm.id
+}
+
+func (tm *testMsg) Data() []byte {
+	return []byte(tm.value)
+}
+
+func (tm *testMsg) Attributes() map[string]string {
+	return tm.attributes
+}
+
+func (tm *testMsg) PublishTime() time.Time {
+	return tm.publishTime
+}
+
+type testTracker struct {
+	sync.Mutex
+	*sync.Cond
+
+	numAcks  int
+	numNacks int
+}
+
+func (t *testTracker) WaitForAck(num int) {
+	t.Lock()
+	if t.Cond == nil {
+		t.Cond = sync.NewCond(&t.Mutex)
+	}
+	for t.numAcks < num {
+		t.Wait()
+	}
+	t.Unlock()
+}
+
+func (t *testTracker) WaitForNack(num int) {
+	t.Lock()
+	if t.Cond == nil {
+		t.Cond = sync.NewCond(&t.Mutex)
+	}
+	for t.numNacks < num {
+		t.Wait()
+	}
+	t.Unlock()
+}
+
+func (t *testTracker) Ack() {
+	t.Lock()
+	defer t.Unlock()
+
+	t.numAcks++
+}
+
+func (t *testTracker) Nack() {
+	t.Lock()
+	defer t.Unlock()
+
+	t.numNacks++
+}