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events/queue: Don't return queue error when closed (#106)
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`Enqueue` and `Dequeue` returned an error which was cumbersome for
consumers to need to check and deal with. The only time this error would
occur would be when the queue was closed, so instead of returning an
error we simply ignore the queue event.

Signed-off-by: joshvanl <[email protected]>
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@JoshVanL
JoshVanL authored Oct 7, 2024
1 parent 2d6ff15 commit bc3a4f0
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Showing 2 changed files with 21 additions and 46 deletions.
16 changes: 4 additions & 12 deletions events/queue/processor.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,17 +14,13 @@ limitations under the License.
package queue

import (
"errors"
"sync"
"sync/atomic"
"time"

kclock "k8s.io/utils/clock"
)

// ErrProcessorStopped is returned when the processor is not running.
var ErrProcessorStopped = errors.New("processor is stopped")

// Processor manages the queue of items and processes them at the correct time.
type Processor[K comparable, T queueable[K]] struct {
executeFn func(r T)
Expand Down Expand Up @@ -59,9 +55,9 @@ func (p *Processor[K, T]) WithClock(clock kclock.Clock) *Processor[K, T] {

// Enqueue adds a new item to the queue.
// If a item with the same ID already exists, it'll be replaced.
func (p *Processor[K, T]) Enqueue(r T) error {
func (p *Processor[K, T]) Enqueue(r T) {
if p.stopped.Load() {
return ErrProcessorStopped
return
}

// Insert or replace the item in the queue
Expand All @@ -74,14 +70,12 @@ func (p *Processor[K, T]) Enqueue(r T) error {
isFirst = isFirst || (peek == r) // This is also going to be true if the item just added landed at the front of the queue
p.process(isFirst)
p.lock.Unlock()

return nil
}

// Dequeue removes a item from the queue.
func (p *Processor[K, T]) Dequeue(key K) error {
func (p *Processor[K, T]) Dequeue(key K) {
if p.stopped.Load() {
return ErrProcessorStopped
return
}

// We need to check if this is the next item in the queue, as that requires stopping the processor
Expand All @@ -93,8 +87,6 @@ func (p *Processor[K, T]) Dequeue(key K) error {
p.process(true)
}
p.lock.Unlock()

return nil
}

// Close stops the processor.
Expand Down
51 changes: 17 additions & 34 deletions events/queue/processor_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -63,10 +63,9 @@ func TestProcessor(t *testing.T) {

t.Run("enqueue items", func(t *testing.T) {
for i := 1; i <= 5; i++ {
err := processor.Enqueue(
processor.Enqueue(
newTestItem(i, clock.Now().Add(time.Second*time.Duration(i))),
)
require.NoError(t, err)
}

// Advance tickers by 500ms to start
Expand All @@ -83,8 +82,7 @@ func TestProcessor(t *testing.T) {

t.Run("enqueue item to be executed right away", func(t *testing.T) {
r := newTestItem(1, clock.Now())
err := processor.Enqueue(r)
require.NoError(t, err)
processor.Enqueue(r)

clock.Step(500 * time.Millisecond)

Expand All @@ -95,10 +93,9 @@ func TestProcessor(t *testing.T) {
t.Run("enqueue item at the front of the queue", func(t *testing.T) {
// Enqueue 4 items
for i := 1; i <= 4; i++ {
err := processor.Enqueue(
processor.Enqueue(
newTestItem(i, clock.Now().Add(time.Second*time.Duration(i))),
)
require.NoError(t, err)
}

assert.Eventually(t, clock.HasWaiters, time.Second, 100*time.Millisecond)
Expand All @@ -111,10 +108,9 @@ func TestProcessor(t *testing.T) {
assert.Equal(t, "1", received.Name)

// Add a new item at the front of the queue
err := processor.Enqueue(
processor.Enqueue(
newTestItem(99, clock.Now()),
)
require.NoError(t, err)

// Advance tickers and assert messages are coming in order
for i := 1; i <= 4; i++ {
Expand All @@ -136,19 +132,16 @@ func TestProcessor(t *testing.T) {

// Enqueue 5 items
for i := 1; i <= 5; i++ {
err := processor.Enqueue(
processor.Enqueue(
newTestItem(i, clock.Now().Add(time.Second*time.Duration(i))),
)
require.NoError(t, err)
}
assert.Equal(t, 5, processor.queue.Len())

// Dequeue items 2 and 4
// Note that this is a string because it's the key
err := processor.Dequeue("2")
require.NoError(t, err)
err = processor.Dequeue("4")
require.NoError(t, err)
processor.Dequeue("2")
processor.Dequeue("4")

assert.Equal(t, 3, processor.queue.Len())

Expand All @@ -173,10 +166,9 @@ func TestProcessor(t *testing.T) {
t.Run("dequeue item from the front of the queue", func(t *testing.T) {
// Enqueue 6 items
for i := 1; i <= 6; i++ {
err := processor.Enqueue(
processor.Enqueue(
newTestItem(i, clock.Now().Add(time.Second*time.Duration(i))),
)
require.NoError(t, err)
}

// Advance tickers and assert messages are coming in order
Expand All @@ -187,8 +179,7 @@ func TestProcessor(t *testing.T) {
if i == 2 || i == 5 {
// Dequeue the item at the front of the queue
// Note that this is a string because it's the key
err := processor.Dequeue(strconv.Itoa(i))
require.NoError(t, err)
processor.Dequeue(strconv.Itoa(i))

// Skip items that have been removed
t.Logf("Should not receive signal %d", i)
Expand All @@ -206,15 +197,13 @@ func TestProcessor(t *testing.T) {
t.Run("replace item", func(t *testing.T) {
// Enqueue 5 items
for i := 1; i <= 5; i++ {
err := processor.Enqueue(
processor.Enqueue(
newTestItem(i, clock.Now().Add(time.Second*time.Duration(i))),
)
require.NoError(t, err)
}

// Replace item 4, bumping its priority down
err := processor.Enqueue(newTestItem(4, clock.Now().Add(6*time.Second)))
require.NoError(t, err)
processor.Enqueue(newTestItem(4, clock.Now().Add(6*time.Second)))

// Advance tickers and assert messages are coming in order
for i := 1; i <= 6; i++ {
Expand All @@ -241,10 +230,9 @@ func TestProcessor(t *testing.T) {
t.Run("replace item at the front of the queue", func(t *testing.T) {
// Enqueue 5 items
for i := 1; i <= 5; i++ {
err := processor.Enqueue(
processor.Enqueue(
newTestItem(i, clock.Now().Add(time.Second*time.Duration(i))),
)
require.NoError(t, err)
}

// Advance tickers and assert messages are coming in order
Expand All @@ -253,8 +241,7 @@ func TestProcessor(t *testing.T) {

if i == 2 {
// Replace item 2, bumping its priority down, while it's at the front of the queue
err := processor.Enqueue(newTestItem(2, clock.Now().Add(5*time.Second)))
require.NoError(t, err)
processor.Enqueue(newTestItem(2, clock.Now().Add(5*time.Second)))

// This item has been pushed down
t.Logf("Should not receive signal %d now", i)
Expand Down Expand Up @@ -287,8 +274,7 @@ func TestProcessor(t *testing.T) {
go func(i int) {
defer wg.Done()
execTime := now.Add(time.Second * time.Duration(rand.Intn(maxDelay))) //nolint:gosec
err := processor.Enqueue(newTestItem(i, execTime))
require.NoError(t, err)
processor.Enqueue(newTestItem(i, execTime))
}(i)
}
wg.Wait()
Expand Down Expand Up @@ -332,10 +318,9 @@ func TestProcessor(t *testing.T) {
t.Run("stop processor", func(t *testing.T) {
// Enqueue 5 items
for i := 1; i <= 5; i++ {
err := processor.Enqueue(
processor.Enqueue(
newTestItem(i, clock.Now().Add(time.Second*time.Duration(i))),
)
require.NoError(t, err)
}

assert.Eventually(t, clock.HasWaiters, time.Second, 100*time.Millisecond)
Expand All @@ -348,10 +333,8 @@ func TestProcessor(t *testing.T) {
assertNoExecutedItem(t)

// Enqueuing and dequeueing should fail
err := processor.Enqueue(newTestItem(99, clock.Now()))
require.ErrorIs(t, err, ErrProcessorStopped)
err = processor.Dequeue("99")
require.ErrorIs(t, err, ErrProcessorStopped)
processor.Enqueue(newTestItem(99, clock.Now()))
processor.Dequeue("99")

// Stopping again is a nop (should not crash)
require.NoError(t, processor.Close())
Expand Down

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