[API] [Misc]: Support LRU cache with TTL for prefix cache indexer (#905)

* feat: add lru cache to support prefix cache indexer

Signed-off-by: vie-serendipity <[email protected]>

Author: vie-serendipity

go.mod

@@ -25,6 +25,7 @@ require (
 	github.com/stretchr/testify v1.9.0
 	google.golang.org/grpc v1.65.0
 	k8s.io/api v0.31.2
+	k8s.io/apiextensions-apiserver v0.31.2
 	k8s.io/apimachinery v0.31.2
 	k8s.io/client-go v0.31.2
 	k8s.io/code-generator v0.31.2
@@ -107,7 +108,6 @@ require (
 	gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
-	k8s.io/apiextensions-apiserver v0.31.2 // indirect
 	k8s.io/gengo/v2 v2.0.0-20240228010128-51d4e06bde70 // indirect
 	sigs.k8s.io/json v0.0.0-20221116044647-bc3834ca7abd // indirect
 	sigs.k8s.io/yaml v1.4.0 // indirect

go.sum

@@ -159,8 +159,6 @@ github.com/redis/go-redis/v9 v9.6.1 h1:HHDteefn6ZkTtY5fGUE8tj8uy85AHk6zP7CpzIAM0
 github.com/redis/go-redis/v9 v9.6.1/go.mod h1:0C0c6ycQsdpVNQpxb1njEQIqkx5UcsM8FJCQLgE9+RA=
 github.com/rogpeppe/go-internal v1.12.0 h1:exVL4IDcn6na9z1rAb56Vxr+CgyK3nn3O+epU5NdKM8=
 github.com/rogpeppe/go-internal v1.12.0/go.mod h1:E+RYuTGaKKdloAfM02xzb0FW3Paa99yedzYV+kq4uf4=
-github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72 h1:qLC7fQah7D6K1B0ujays3HV9gkFtllcxhzImRR7ArPQ=
-github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

pkg/plugins/gateway/cache/lru_store.go

@@ -0,0 +1,173 @@
+/*
+Copyright 2025 The Aibrix Team.
+
+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 cache
+
+import (
+	"sync"
+	"time"
+)
+
+type getCurrentTime func() time.Time
+
+var DefaultGetCurrentTime = func() time.Time {
+	return time.Now()
+}
+
+type LRUStore[K comparable, V any] struct {
+	sync.RWMutex
+	freeTable map[K]*entry[K, V]
+	lruList   *list[K, V]
+	cap       int
+
+	getCurrentTime
+	interval time.Duration
+	ttl      time.Duration
+}
+
+func NewLRUStore[K comparable, V any](cap int, ttl, interval time.Duration, f getCurrentTime) *LRUStore[K, V] {
+	store := &LRUStore[K, V]{
+		freeTable:      make(map[K]*entry[K, V]),
+		lruList:        &list[K, V]{head: &entry[K, V]{}, tail: &entry[K, V]{}},
+		cap:            cap,
+		ttl:            ttl,
+		interval:       interval,
+		getCurrentTime: f,
+	}
+	store.lruList.head.next = store.lruList.tail
+	store.lruList.tail.prev = store.lruList.head
+
+	go store.startEviction()
+	return store
+}
+
+func (e *LRUStore[K, V]) startEviction() {
+	ticker := time.NewTicker(e.interval)
+	defer ticker.Stop()
+	for range ticker.C {
+		e.evict(e.getCurrentTime())
+	}
+}
+
+func (e *LRUStore[K, V]) Put(key K, value V) bool {
+	e.Lock()
+	defer e.Unlock()
+
+	if entry, exists := e.freeTable[key]; exists {
+		entry.lastAccessTime = time.Now()
+		entry.Value = value
+		e.lruList.moveToHead(entry)
+		return false
+	}
+
+	entry := &entry[K, V]{Key: key, Value: value, lastAccessTime: time.Now()}
+	e.lruList.addToHead(entry)
+	e.freeTable[key] = entry
+	if len(e.freeTable) > e.cap {
+		removed := e.lruList.removeTail()
+		if removed == nil {
+			return false
+		}
+		delete(e.freeTable, removed.Key)
+		return true
+	}
+	return false
+}
+
+func (e *LRUStore[K, V]) Get(key K) (V, bool) {
+	e.Lock()
+	defer e.Unlock()
+
+	if entry, exists := e.freeTable[key]; exists {
+		entry.lastAccessTime = time.Now()
+		e.lruList.moveToHead(entry)
+		return entry.Value, true
+	}
+	var zero V
+	return zero, false
+}
+
+func (e *LRUStore[K, V]) Len() int {
+	e.RLock()
+	defer e.RUnlock()
+	return len(e.freeTable)
+}
+
+func (e *LRUStore[K, V]) evict(now time.Time) {
+	var keysToEvict []K
+
+	e.RLock()
+	for key, entry := range e.freeTable {
+		if now.Sub(entry.lastAccessTime) > e.ttl {
+			keysToEvict = append(keysToEvict, key)
+		}
+	}
+	e.RUnlock()
+
+	for _, key := range keysToEvict {
+		e.Lock()
+		if entry, exists := e.freeTable[key]; exists && now.Sub(entry.lastAccessTime) > e.ttl {
+			e.lruList.remove(entry)
+			delete(e.freeTable, key)
+		}
+		e.Unlock()
+	}
+}
+
+type entry[K comparable, V any] struct {
+	Key            K
+	Value          V
+	prev           *entry[K, V]
+	next           *entry[K, V]
+	lastAccessTime time.Time
+}
+
+type list[K comparable, V any] struct {
+	head *entry[K, V]
+	tail *entry[K, V]
+}
+
+func (l *list[K, V]) addToHead(e *entry[K, V]) {
+	e.prev = l.head
+	e.next = l.head.next
+	l.head.next.prev = e
+	l.head.next = e
+}
+
+func (l *list[K, V]) moveToHead(e *entry[K, V]) {
+	l.remove(e)
+	l.addToHead(e)
+}
+
+func (l *list[K, V]) remove(e *entry[K, V]) {
+	if e.prev != nil {
+		e.prev.next = e.next
+	}
+	if e.next != nil {
+		e.next.prev = e.prev
+	}
+	e.prev = nil
+	e.next = nil
+}
+
+func (l *list[K, V]) removeTail() *entry[K, V] {
+	if l.tail.prev == l.head {
+		return nil
+	}
+	entry := l.tail.prev
+	l.remove(entry)
+	return entry
+}

pkg/plugins/gateway/cache/lru_store_test.go

@@ -0,0 +1,105 @@
+/*
+Copyright 2025 The Aibrix Team.
+
+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 cache
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+// TODO: add performance benchmark tests
+func TestLRUStore_PutAndGet(t *testing.T) {
+	store := NewLRUStore[string, string](2, 5*time.Second, 1*time.Second, DefaultGetCurrentTime)
+
+	// Test adding and retrieving items
+	store.Put("key1", "value1")
+	store.Put("key2", "value2")
+
+	if val, ok := store.Get("key1"); !ok || val != "value1" {
+		t.Errorf("expected value1, got %v", val)
+	}
+
+	if val, ok := store.Get("key2"); !ok || val != "value2" {
+		t.Errorf("expected value2, got %v", val)
+	}
+
+	store.Put("key3", "value3")
+	if _, ok := store.Get("key1"); ok {
+		t.Errorf("expected key1 to be evicted")
+	}
+
+	if val, ok := store.Get("key3"); !ok || val != "value3" {
+		t.Errorf("expected value3, got %v", val)
+	}
+}
+
+func TestLRUStore_TTL(t *testing.T) {
+	store := NewLRUStore[string, string](2, 2*time.Second, 1*time.Second, DefaultGetCurrentTime)
+
+	// Test TTL expiration
+	store.Put("key1", "value1")
+	time.Sleep(3 * time.Second) // Wait for TTL to expire
+
+	if _, ok := store.Get("key1"); ok {
+		t.Errorf("expected key1 to be expired")
+	}
+}
+
+func TestLRUStore_UpdateExistingKey(t *testing.T) {
+	store := NewLRUStore[string, string](2, 5*time.Second, 1*time.Second, DefaultGetCurrentTime)
+
+	// Test updating an existing key
+	store.Put("key1", "value1")
+	store.Put("key1", "value2")
+
+	if val, ok := store.Get("key1"); !ok || val != "value2" {
+		t.Errorf("expected value2, got %v", val)
+	}
+}
+
+func TestLRUStore_ConcurrentEvictions(t *testing.T) {
+	store := NewLRUStore[string, string](5, 5*time.Second, 1*time.Second, DefaultGetCurrentTime) // Small capacity to force evictions
+
+	const numGoroutines = 10
+	const numOperations = 20
+	done := make(chan error, numGoroutines)
+	defer close(done)
+
+	for i := range numGoroutines {
+		go func(id int) {
+			for j := range numOperations {
+				key := fmt.Sprintf("goroutine%d_key%d", id, j)
+				value := fmt.Sprintf("value%d", j)
+
+				store.Put(key, value)
+
+				if store.Len() > store.cap {
+					done <- fmt.Errorf("store exceeded capacity: expected at most %d, got %d", store.cap, len(store.freeTable))
+					break
+				}
+			}
+			done <- nil
+		}(i)
+	}
+
+	for range numGoroutines {
+		if err := <-done; err != nil {
+			t.Error(err)
+		}
+	}
+}

pkg/plugins/gateway/cache/store.go

@@ -0,0 +1,22 @@
+/*
+Copyright 2025 The Aibrix Team.
+
+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 cache
+
+type Store[K comparable, V any] interface {
+	Put(key K, value V) bool
+	Get(key K) (V, bool)
+	Len() int
+}