Add support for multiple subscribers to CRI container events

Signed-off-by: Derek McGowan <derek@mcg.dev>

internal/eventq/eventq_test.go

@@ -0,0 +1,152 @@
+/*
+   Copyright The containerd 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 eventq
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSingleSubscriber(t *testing.T) {
+	eq := New[int](time.Second, func(int) {})
+	c := newCollector(eq)
+	expected := []int{1, 2, 3, 4, 5}
+	for _, i := range expected {
+		eq.Send(i)
+	}
+	eq.Shutdown()
+	assert.Equal(t, expected, c.Collected())
+}
+
+func TestMultiSubscriber(t *testing.T) {
+	eq := New[int](time.Second, func(int) {})
+	cs := make([]*collector, 10)
+	for i := range cs {
+		cs[i] = newCollector(eq)
+	}
+	expected := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
+	for _, i := range expected {
+		eq.Send(i)
+	}
+	eq.Shutdown()
+	for i := range cs {
+		assert.Equal(t, expected, cs[i].Collected())
+	}
+}
+
+func TestMissedEvents(t *testing.T) {
+	eq := New[int](3600*time.Second, func(int) {})
+	expected := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
+	for _, i := range expected[:2] {
+		eq.Send(i)
+	}
+	c := newCollector(eq)
+	for _, i := range expected[2:] {
+		eq.Send(i)
+	}
+
+	eq.Shutdown()
+	assert.Equal(t, expected, c.Collected())
+}
+
+func TestSubscribersDifferentTime(t *testing.T) {
+	eq := New[int](time.Second, func(int) {})
+	expected := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
+	c1 := newCollector(eq)
+	for _, i := range expected[:2] {
+		eq.Send(i)
+	}
+	c2 := newCollector(eq)
+	for _, i := range expected[2:] {
+		eq.Send(i)
+	}
+
+	eq.Shutdown()
+	assert.Equal(t, expected, c1.Collected())
+	assert.Equal(t, expected[2:], c2.Collected())
+}
+
+func TestDiscardedAfterTime(t *testing.T) {
+	discarded := []int{}
+	eq := New[int](time.Microsecond, func(i int) {
+		discarded = append(discarded, i)
+	})
+	expected := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
+	for _, i := range expected[:2] {
+		eq.Send(i)
+	}
+	time.Sleep(50 * time.Millisecond)
+	c := newCollector(eq)
+	for _, i := range expected[2:] {
+		eq.Send(i)
+	}
+
+	eq.Shutdown()
+	assert.Equal(t, expected[:2], discarded)
+	assert.Equal(t, expected[2:], c.Collected())
+}
+
+func TestDiscardedAtShutdown(t *testing.T) {
+	discarded := []int{}
+	expected := []int{1, 2, 3, 4, 5, 6, 7, 8, 9}
+	done := make(chan struct{})
+	eq := New[int](3600*time.Second, func(i int) {
+		discarded = append(discarded, i)
+		if len(discarded) == len(expected) {
+			close(done)
+		}
+	})
+	for _, i := range expected {
+		eq.Send(i)
+	}
+	eq.Shutdown()
+	select {
+	case <-done:
+	case <-time.After(time.Second):
+	}
+	assert.Equal(t, expected, discarded)
+}
+
+type collector struct {
+	collected []int
+	c         <-chan int
+	done      chan struct{}
+}
+
+func newCollector(eq EventQueue[int]) *collector {
+	eventC, closer := eq.Subscribe()
+	c := &collector{
+		c:    eventC,
+		done: make(chan struct{}),
+	}
+	go func() {
+		defer close(c.done)
+		defer closer.Close()
+		for i := range c.c {
+			c.collected = append(c.collected, i)
+		}
+	}()
+
+	return c
+}
+
+func (c *collector) Collected() []int {
+	<-c.done
+	return c.collected
+}