diff --git a/internal/caches/list.go b/internal/caches/list.go
index 57b1877..4b625e1 100644
--- a/internal/caches/list.go
+++ b/internal/caches/list.go
@@ -4,8 +4,10 @@ import "sync"
 
 // 缓存列表管理
 type List struct {
-	m      map[string]*Item // hash => item
-	locker sync.RWMutex
+	m        map[string]*Item // hash => item
+	locker   sync.RWMutex
+	onAdd    func(item *Item)
+	onRemove func(item *Item)
 }
 
 func NewList() *List {
@@ -22,6 +24,9 @@ func (this *List) Reset() {
 
 func (this *List) Add(hash string, item *Item) {
 	this.locker.Lock()
+	if this.onAdd != nil {
+		this.onAdd(item)
+	}
 	this.m[hash] = item
 	this.locker.Unlock()
 }
@@ -40,7 +45,15 @@ func (this *List) Exist(hash string) bool {
 
 func (this *List) Remove(hash string) {
 	this.locker.Lock()
-	delete(this.m, hash)
+
+	item, ok := this.m[hash]
+	if ok {
+		if this.onRemove != nil {
+			this.onRemove(item)
+		}
+		delete(this.m, hash)
+	}
+
 	this.locker.Unlock()
 }
 
@@ -56,6 +69,9 @@ func (this *List) Purge(count int, callback func(hash string)) {
 		}
 
 		if item.IsExpired() {
+			if this.onRemove != nil {
+				this.onRemove(item)
+			}
 			delete(this.m, hash)
 			deletedHashList = append(deletedHashList, hash)
 		}
@@ -100,3 +116,13 @@ func (this *List) Count() int64 {
 	this.locker.RUnlock()
 	return count
 }
+
+// 添加事件
+func (this *List) OnAdd(f func(item *Item)) {
+	this.onAdd = f
+}
+
+// 删除事件
+func (this *List) OnRemove(f func(item *Item)) {
+	this.onRemove = f
+}
diff --git a/internal/caches/storage_file.go b/internal/caches/storage_file.go
index a5750b6..0947769 100644
--- a/internal/caches/storage_file.go
+++ b/internal/caches/storage_file.go
@@ -18,6 +18,7 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 )
 
@@ -35,6 +36,7 @@ var (
 type FileStorage struct {
 	policy      *serverconfigs.HTTPCachePolicy
 	cacheConfig *serverconfigs.HTTPFileCacheStorage
+	totalSize   int64
 
 	list   *List
 	locker sync.RWMutex
@@ -55,6 +57,13 @@ func (this *FileStorage) Policy() *serverconfigs.HTTPCachePolicy {
 
 // 初始化
 func (this *FileStorage) Init() error {
+	this.list.OnAdd(func(item *Item) {
+		atomic.AddInt64(&this.totalSize, item.Size)
+	})
+	this.list.OnRemove(func(item *Item) {
+		atomic.AddInt64(&this.totalSize, -item.Size)
+	})
+
 	this.locker.Lock()
 	defer this.locker.Unlock()
 
@@ -222,7 +231,10 @@ func (this *FileStorage) Read(key string, readerBuf []byte, callback func(data [
 func (this *FileStorage) Open(key string, expiredAt int64) (Writer, error) {
 	// 检查是否超出最大值
 	if this.policy.MaxKeys > 0 && this.list.Count() > this.policy.MaxKeys {
-		return nil, errors.New("too many keys in cache storage")
+		return nil, errors.New("write file cache failed: too many keys in cache storage")
+	}
+	if this.policy.CapacityBytes() > 0 && this.policy.CapacityBytes() <= this.totalSize {
+		return nil, errors.New("write file cache failed: over disk size, real size: " + strconv.FormatInt(this.totalSize, 10) + " bytes")
 	}
 
 	hash := stringutil.Md5(key)
@@ -240,6 +252,9 @@ func (this *FileStorage) Open(key string, expiredAt int64) (Writer, error) {
 
 	this.locker.Lock()
 
+	// 先删除
+	this.list.Remove(hash)
+
 	path := dir + "/" + hash + ".cache"
 	writer, err := os.OpenFile(path, os.O_CREATE|os.O_TRUNC|os.O_SYNC|os.O_WRONLY, 0777)
 	if err != nil {
diff --git a/internal/caches/storage_memory.go b/internal/caches/storage_memory.go
index 99bc5b1..5db81b6 100644
--- a/internal/caches/storage_memory.go
+++ b/internal/caches/storage_memory.go
@@ -8,6 +8,7 @@ import (
 	"github.com/dchest/siphash"
 	"strconv"
 	"sync"
+	"sync/atomic"
 	"time"
 )
 
@@ -19,11 +20,11 @@ type MemoryItem struct {
 type MemoryStorage struct {
 	policy        *serverconfigs.HTTPCachePolicy
 	list          *List
-	totalSize     int64 // 需要实现
 	locker        *sync.RWMutex
 	valuesMap     map[uint64]*MemoryItem
 	ticker        *utils.Ticker
 	purgeDuration time.Duration
+	totalSize     int64
 }
 
 func NewMemoryStorage(policy *serverconfigs.HTTPCachePolicy) *MemoryStorage {
@@ -37,6 +38,13 @@ func NewMemoryStorage(policy *serverconfigs.HTTPCachePolicy) *MemoryStorage {
 
 // 初始化
 func (this *MemoryStorage) Init() error {
+	this.list.OnAdd(func(item *Item) {
+		atomic.AddInt64(&this.totalSize, item.Size)
+	})
+	this.list.OnRemove(func(item *Item) {
+		atomic.AddInt64(&this.totalSize, -item.Size)
+	})
+
 	if this.purgeDuration <= 0 {
 		this.purgeDuration = 30 * time.Second
 	}
@@ -64,6 +72,7 @@ func (this *MemoryStorage) Read(key string, readerBuf []byte, callback func(data
 	}
 
 	if item.ExpiredAt > utils.UnixTime() {
+		// 这时如果callback处理比较慢的话，可能会影响性能，但目前没有更好的解决方案
 		callback(item.Value, int64(len(item.Value)), item.ExpiredAt, true)
 		this.locker.RUnlock()
 		return nil
@@ -79,7 +88,16 @@ func (this *MemoryStorage) Read(key string, readerBuf []byte, callback func(data
 func (this *MemoryStorage) Open(key string, expiredAt int64) (Writer, error) {
 	// 检查是否超出最大值
 	if this.policy.MaxKeys > 0 && this.list.Count() > this.policy.MaxKeys {
-		return nil, errors.New("too many keys in cache storage")
+		return nil, errors.New("write memory cache failed: too many keys in cache storage")
+	}
+	if this.policy.CapacityBytes() > 0 && this.policy.CapacityBytes() <= this.totalSize {
+		return nil, errors.New("write memory cache failed: over memory size, real size: " + strconv.FormatInt(this.totalSize, 10) + " bytes")
+	}
+
+	// 先删除
+	err := this.Delete(key)
+	if err != nil {
+		return nil, err
 	}
 
 	return NewMemoryWriter(this.valuesMap, key, expiredAt, this.locker), nil
@@ -110,6 +128,7 @@ func (this *MemoryStorage) CleanAll() error {
 	this.locker.Lock()
 	this.valuesMap = map[uint64]*MemoryItem{}
 	this.list.Reset()
+	atomic.StoreInt64(&this.totalSize, 0)
 	this.locker.Unlock()
 	return nil
 }
@@ -144,7 +163,7 @@ func (this *MemoryStorage) Policy() *serverconfigs.HTTPCachePolicy {
 
 // 将缓存添加到列表
 func (this *MemoryStorage) AddToList(item *Item) {
-	item.Size = item.ValueSize + int64(len(item.Key))
+	item.Size = item.ValueSize + int64(len(item.Key)) + 32 /** 32是我们评估的数据结构的长度 **/
 	hash := fmt.Sprintf("%d", this.hash(item.Key))
 	this.list.Add(hash, item)
 }
diff --git a/internal/caches/writer_memory.go b/internal/caches/writer_memory.go
index 8781d33..e15bb6c 100644
--- a/internal/caches/writer_memory.go
+++ b/internal/caches/writer_memory.go
@@ -43,6 +43,7 @@ func (this *MemoryWriter) Write(data []byte) (n int, err error) {
 		item.Value = append([]byte{}, data...)
 		item.ExpiredAt = this.expiredAt
 		this.m[hash] = item
+		this.isFirstWriting = false
 	}
 	this.locker.Unlock()
 	return len(data), nil
diff --git a/internal/nodes/http_request_cache.go b/internal/nodes/http_request_cache.go
index fb90dcf..a507ed9 100644
--- a/internal/nodes/http_request_cache.go
+++ b/internal/nodes/http_request_cache.go
@@ -147,5 +147,6 @@ func (this *HTTPRequest) doCacheRead() (shouldStop bool) {
 		return
 	}
 
+	this.cacheRef = nil // 终止读取不再往下传递
 	return true
 }
diff --git a/internal/nodes/http_writer.go b/internal/nodes/http_writer.go
index 37aa2c0..e558f3b 100644
--- a/internal/nodes/http_writer.go
+++ b/internal/nodes/http_writer.go
@@ -114,6 +114,7 @@ func (this *HTTPWriter) Write(data []byte) (n int, err error) {
 			_, err = this.cacheWriter.Write(data)
 			if err != nil {
 				_ = this.cacheWriter.Discard()
+				this.cacheWriter = nil
 				logs.Println("write cache failed: " + err.Error())
 			}
 		}