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fix: correctly notify auto-cleaner when an item's TTL is shortened #206

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Merged
swithek merged 2 commits into from
Jun 22, 2026
Merged

fix: correctly notify auto-cleaner when an item's TTL is shortened #206

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00b6ba4
autocleaner should respect new ttl if head is updated
PiAreSquared Apr 24, 2026
2e6c14a
refactor to table-driven test
PiAreSquared Jun 20, 2026
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30 changes: 21 additions & 9 deletions cache.go
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Original file line number Diff line number Diff line change
Expand Up @@ -88,14 +88,11 @@ func New[K comparable, V any](opts ...Option[K, V]) *Cache[K, V] {

// updateExpirations updates the expiration queue and notifies
// the cache auto cleaner if needed.
// 'oldExpiresAt' should reflect the front of the expiration queue
// before any item mutations.
// Not safe for concurrent use by multiple goroutines without additional
// locking.
func (c *Cache[K, V]) updateExpirations(fresh bool, elem *list.Element) {
var oldExpiresAt time.Time

if !c.items.expQueue.isEmpty() {
oldExpiresAt = c.items.expQueue[0].Value.(*Item[K, V]).expiresAt
}
func (c *Cache[K, V]) updateExpirations(fresh bool, elem *list.Element, oldExpiresAt time.Time) {

if fresh {
c.items.expQueue.push(elem)
Expand Down Expand Up @@ -151,9 +148,14 @@ func (c *Cache[K, V]) set(key K, value V, ttl time.Duration) *Item[K, V] {
item := elem.Value.(*Item[K, V])
oldItemCost := item.cost

var oldExpiresAt time.Time
if !c.items.expQueue.isEmpty() {
oldExpiresAt = c.items.expQueue[0].Value.(*Item[K, V]).expiresAt
}

item.update(value, ttl)

c.updateExpirations(false, elem)
c.updateExpirations(false, elem, oldExpiresAt)

if c.options.maxCost != 0 {
c.cost = c.cost - oldItemCost + item.cost
Expand Down Expand Up @@ -185,11 +187,16 @@ func (c *Cache[K, V]) set(key K, value V, ttl time.Duration) *Item[K, V] {
ttl = c.options.ttl
}

var oldExpiresAt time.Time
if !c.items.expQueue.isEmpty() {
oldExpiresAt = c.items.expQueue[0].Value.(*Item[K, V]).expiresAt
}

// create a new item
item := NewItemWithOpts(key, value, ttl, c.options.itemOpts...)
elem = c.items.lru.PushFront(item)
c.items.values[key] = elem
c.updateExpirations(true, elem)
c.updateExpirations(true, elem, oldExpiresAt)

if c.options.maxCost != 0 {
c.cost += item.cost
Expand Down Expand Up @@ -231,8 +238,13 @@ func (c *Cache[K, V]) get(key K, touch bool, includeExpired bool) *list.Element
c.items.lru.MoveToFront(elem)

if touch && item.ttl > 0 {
var oldExpiresAt time.Time
if !c.items.expQueue.isEmpty() {
oldExpiresAt = c.items.expQueue[0].Value.(*Item[K, V]).expiresAt
}

item.touch()
c.updateExpirations(false, elem)
c.updateExpirations(false, elem, oldExpiresAt)
}

return elem
Expand Down
125 changes: 95 additions & 30 deletions cache_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,7 @@ func Test_Cache_updateExpirations(t *testing.T) {
TimerChValue time.Duration
Fresh bool
EmptyQueue bool
SingleItem bool
OldExpiresAt time.Time
NewExpiresAt time.Time
Result time.Duration
Expand Down Expand Up @@ -115,6 +116,12 @@ func Test_Cache_updateExpirations(t *testing.T) {
NewExpiresAt: newExp,
Result: time.Until(newExp),
},
"Update with non fresh item, single item in queue and shortened expiresAt field": {
SingleItem: true,
OldExpiresAt: oldExp,
NewExpiresAt: newExp,
Result: time.Until(newExp),
},
}

for cn, c := range cc {
Expand All @@ -136,11 +143,13 @@ func Test_Cache_updateExpirations(t *testing.T) {
}

if !c.EmptyQueue {
cache.items.expQueue.push(&list.Element{
Value: &Item[string, string]{
expiresAt: c.OldExpiresAt,
},
})
if !c.SingleItem {
cache.items.expQueue.push(&list.Element{
Value: &Item[string, string]{
expiresAt: c.OldExpiresAt,
},
})
}

if !c.Fresh {
elem = &list.Element{
Expand All @@ -154,7 +163,11 @@ func Test_Cache_updateExpirations(t *testing.T) {
}
}

cache.updateExpirations(c.Fresh, elem)
var oldExpiresAt time.Time
if !c.EmptyQueue {
oldExpiresAt = c.OldExpiresAt
}
cache.updateExpirations(c.Fresh, elem, oldExpiresAt)

var res time.Duration

Expand All @@ -172,13 +185,14 @@ func Test_Cache_set(t *testing.T) {
const newKey, existingKey, evictedKey = "newKey123", "existingKey", "evicted"

cc := map[string]struct {
Capacity uint64
MaxCost uint64
Key string
TTL time.Duration
Metrics Metrics
InsertCalled bool
UpdateCalled bool
Capacity uint64
MaxCost uint64
Key string
TTL time.Duration
Metrics Metrics
InsertCalled bool
UpdateCalled bool
ExpectedTimerNotification time.Duration
}{
"Set with existing key and custom TTL": {
Key: existingKey,
Expand Down Expand Up @@ -294,6 +308,24 @@ func Test_Cache_set(t *testing.T) {
Evictions: 1,
},
},
"Set with existing key and shortened TTL": {
Key: existingKey,
TTL: time.Minute,
Metrics: Metrics{
Updates: 1,
},
UpdateCalled: true,
ExpectedTimerNotification: time.Minute,
},
"Set with new key and shortened TTL": {
Key: newKey,
TTL: time.Minute,
Metrics: Metrics{
Insertions: 1,
},
InsertCalled: true,
ExpectedTimerNotification: time.Minute,
},
}

for cn, c := range cc {
Expand Down Expand Up @@ -384,6 +416,16 @@ func Test_Cache_set(t *testing.T) {
assert.Zero(t, item.expiresAt)
assert.NotEqual(t, c.Key, cache.items.expQueue[0].Value.(*Item[string, string]).key)
}

if c.ExpectedTimerNotification > 0 {
var res time.Duration
select {
case res = <-cache.items.timerCh:
default:
t.Fatal("expected timer notification but channel was empty")
}
assert.InDelta(t, c.ExpectedTimerNotification, res, float64(time.Second))
}
})
}

Expand Down Expand Up @@ -422,28 +464,37 @@ func Test_Cache_get(t *testing.T) {
const existingKey, notFoundKey, expiredKey = "existing", "notfound", "expired"

cc := map[string]struct {
Key string
Touch bool
WithTTL bool
Key string
Touch bool
TTL time.Duration
AddExpiredKey bool
ExpectedTimerNotification time.Duration
}{
"Retrieval of non-existent item": {
Key: notFoundKey,
},
"Retrieval of expired item": {
Key: expiredKey,
Key: expiredKey,
AddExpiredKey: true,
},
"Retrieval of existing item without update": {
Key: existingKey,
},
"Retrieval of existing item with touch and non zero TTL": {
Key: existingKey,
Touch: true,
WithTTL: true,
Key: existingKey,
Touch: true,
TTL: time.Hour * 30,
},
"Retrieval of existing item with touch and zero TTL": {
Key: existingKey,
Touch: true,
},
"Retrieval of existing item with touch and shortened TTL": {
Key: existingKey,
Touch: true,
TTL: time.Millisecond,
ExpectedTimerNotification: time.Millisecond,
},
}

for cn, c := range cc {
Expand All @@ -453,18 +504,16 @@ func Test_Cache_get(t *testing.T) {
t.Parallel()

cache := prepCache(0, time.Hour, existingKey, "test2", "test3")
addExpiredCacheItems(cache, expiredKey)
time.Sleep(time.Millisecond) // force expiration
if c.AddExpiredKey {
addExpiredCacheItems(cache, expiredKey)
time.Sleep(time.Millisecond) // force expiration
}

oldItem := cache.items.values[existingKey].Value.(*Item[string, string])
oldQueueIndex := oldItem.queueIndex
oldExpiresAt := oldItem.expiresAt

if c.WithTTL {
oldItem.ttl = time.Hour * 30
} else {
oldItem.ttl = 0
}
oldItem.ttl = c.TTL

elem := cache.get(c.Key, c.Touch, false)

Expand All @@ -482,14 +531,30 @@ func Test_Cache_get(t *testing.T) {
require.NotNil(t, elem)
item := elem.Value.(*Item[string, string])

if c.Touch && c.WithTTL {
assert.True(t, item.expiresAt.After(oldExpiresAt))
assert.NotEqual(t, oldQueueIndex, item.queueIndex)
if c.Touch && c.TTL > 0 {
if item.expiresAt.Before(oldExpiresAt) {
assert.Equal(t, oldQueueIndex, item.queueIndex)
} else {
assert.True(t, item.expiresAt.After(oldExpiresAt))
assert.NotEqual(t, oldQueueIndex, item.queueIndex)
}
} else {
assert.True(t, item.expiresAt.Equal(oldExpiresAt))
assert.Equal(t, oldQueueIndex, item.queueIndex)
}

select {
case res := <-cache.items.timerCh:
if c.ExpectedTimerNotification == 0 {
t.Fatalf("unexpected timer notification: %v", res)
}
assert.InDelta(t, c.ExpectedTimerNotification, res, float64(time.Second))
default:
if c.ExpectedTimerNotification > 0 {
t.Fatal("expected timer notification but channel was empty")
}
}

assert.Equal(t, c.Key, cache.items.lru.Front().Value.(*Item[string, string]).key)
})
}
Expand Down
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