Add the cache component.

main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	_ "github.com/go-sql-driver/mysql"
+	_ "github.com/muesli/cache2go"
 	"log"
 	"net/http"
 	"tank/rest"
@@ -22,8 +23,8 @@ func main() {
 	info := fmt.Sprintf("App started at http://localhost%v", dotPort)
 	rest.LogInfo(info)
 
-	err := http.ListenAndServe(dotPort, nil)
+	err1 := http.ListenAndServe(dotPort, nil)
-	if err != nil {
+	if err1 != nil {
-		log.Fatal("ListenAndServe: ", err)
+		log.Fatal("ListenAndServe: ", err1)
 	}
 }

rest/cache.go

@@ -0,0 +1,435 @@
+package rest
+
+import (
+	"errors"
+	"fmt"
+	"log"
+	"sort"
+	"sync"
+	"time"
+)
+
+//缓存项
+//主要借鉴了cache2go https://github.com/muesli/cache2go
+type CacheItem struct {
+	sync.RWMutex //读写锁
+
+	//缓存键
+	key interface{}
+	//缓存值
+	data interface{}
+	// 缓存项的生命期
+	lifeSpan time.Duration
+	//创建时间
+	createdOn time.Time
+	//最后访问时间
+	accessedOn time.Time
+	//访问次数
+	accessCount int64
+	// 在删除缓存项之前调用的回调函数
+	aboutToExpire func(key interface{})
+}
+
+//新建一项缓存
+func CreateCacheItem(key interface{}, lifeSpan time.Duration, data interface{}) CacheItem {
+	t := time.Now()
+	return CacheItem{
+		key:           key,
+		lifeSpan:      lifeSpan,
+		createdOn:     t,
+		accessedOn:    t,
+		accessCount:   0,
+		aboutToExpire: nil,
+		data:          data,
+	}
+}
+
+//手动获取一下，保持该项
+func (item *CacheItem) KeepAlive() {
+	item.Lock()
+	defer item.Unlock()
+	item.accessedOn = time.Now()
+	item.accessCount++
+}
+
+//返回生命周期
+func (item *CacheItem) LifeSpan() time.Duration {
+	return item.lifeSpan
+}
+
+//返回访问时间。可能并发，加锁
+func (item *CacheItem) AccessedOn() time.Time {
+	item.RLock()
+	defer item.RUnlock()
+	return item.accessedOn
+}
+
+//返回创建时间
+func (item *CacheItem) CreatedOn() time.Time {
+	return item.createdOn
+}
+
+//返回访问时间。可能并发，加锁
+func (item *CacheItem) AccessCount() int64 {
+	item.RLock()
+	defer item.RUnlock()
+	return item.accessCount
+}
+
+//返回key值
+func (item *CacheItem) Key() interface{} {
+	return item.key
+}
+
+//返回数据
+func (item *CacheItem) Data() interface{} {
+	return item.data
+}
+
+//设置回调函数
+func (item *CacheItem) SetAboutToExpireCallback(f func(interface{})) {
+	item.Lock()
+	defer item.Unlock()
+	item.aboutToExpire = f
+}
+
+// 统一管理缓存项的表
+type CacheTable struct {
+	sync.RWMutex
+
+	//缓存表名
+	name string
+	//所有缓存项
+	items map[interface{}]*CacheItem
+	// 触发缓存清理的定时器
+	cleanupTimer *time.Timer
+	// 缓存清理周期
+	cleanupInterval time.Duration
+	// 该缓存表的日志
+	logger *log.Logger
+	// 获取一个不存在的缓存项时的回调函数
+	loadData func(key interface{}, args ...interface{}) *CacheItem
+	// 向缓存表增加缓存项时的回调函数
+	addedItem func(item *CacheItem)
+	// 从缓存表删除一个缓存项时的回调函数
+	aboutToDeleteItem func(item *CacheItem)
+}
+
+// 返回当缓存中存储有多少项
+func (table *CacheTable) Count() int {
+	table.RLock()
+	defer table.RUnlock()
+	return len(table.items)
+}
+
+// 遍历所有项
+func (table *CacheTable) Foreach(trans func(key interface{}, item *CacheItem)) {
+	table.RLock()
+	defer table.RUnlock()
+
+	for k, v := range table.items {
+		trans(k, v)
+	}
+}
+
+// SetDataLoader配置一个数据加载的回调，当尝试去请求一个不存在的key的时候调用
+func (table *CacheTable) SetDataLoader(f func(interface{}, ...interface{}) *CacheItem) {
+	table.Lock()
+	defer table.Unlock()
+	table.loadData = f
+}
+
+// 添加时的回调函数
+func (table *CacheTable) SetAddedItemCallback(f func(*CacheItem)) {
+	table.Lock()
+	defer table.Unlock()
+	table.addedItem = f
+}
+
+// 删除时的回调函数
+func (table *CacheTable) SetAboutToDeleteItemCallback(f func(*CacheItem)) {
+	table.Lock()
+	defer table.Unlock()
+	table.aboutToDeleteItem = f
+}
+
+// 设置缓存表需要使用的log
+func (table *CacheTable) SetLogger(logger *log.Logger) {
+	table.Lock()
+	defer table.Unlock()
+	table.logger = logger
+}
+
+//终结检查，被自调整的时间触发
+func (table *CacheTable) expirationCheck() {
+	table.Lock()
+	if table.cleanupTimer != nil {
+		table.cleanupTimer.Stop()
+	}
+	if table.cleanupInterval > 0 {
+		table.log("Expiration check triggered after", table.cleanupInterval, "for table", table.name)
+	} else {
+		table.log("Expiration check installed for table", table.name)
+	}
+
+	// 为了不抢占锁，采用临时的items.
+	items := table.items
+	table.Unlock()
+
+	//为了定时器更准确，我们需要在每一个循环中更新‘now’，不确定是否是有效率的。
+	now := time.Now()
+	smallestDuration := 0 * time.Second
+	for key, item := range items {
+		// 取出我们需要的东西，为了不抢占锁
+		item.RLock()
+		lifeSpan := item.lifeSpan
+		accessedOn := item.accessedOn
+		item.RUnlock()
+
+		// 0永久有效
+		if lifeSpan == 0 {
+			continue
+		}
+		if now.Sub(accessedOn) >= lifeSpan {
+			//缓存项已经过期
+			_, e := table.Delete(key)
+			if e != nil {
+				table.log("删除缓存项时出错 ", e.Error())
+			}
+		} else {
+			//查找最靠近结束生命周期的项目
+			if smallestDuration == 0 || lifeSpan-now.Sub(accessedOn) < smallestDuration {
+				smallestDuration = lifeSpan - now.Sub(accessedOn)
+			}
+		}
+	}
+
+	// 为下次清理设置间隔，自触发机制
+	table.Lock()
+	table.cleanupInterval = smallestDuration
+	if smallestDuration > 0 {
+		table.cleanupTimer = time.AfterFunc(smallestDuration, func() {
+			go table.expirationCheck()
+		})
+	}
+	table.Unlock()
+}
+
+// 添加缓存项
+func (table *CacheTable) Add(key interface{}, lifeSpan time.Duration, data interface{}) *CacheItem {
+	item := CreateCacheItem(key, lifeSpan, data)
+
+	// 将缓存项放入表中
+	table.Lock()
+	table.log("Adding item with key", key, "and lifespan of", lifeSpan, "to table", table.name)
+	table.items[key] = &item
+
+	// 取出需要的东西，释放锁
+	expDur := table.cleanupInterval
+	addedItem := table.addedItem
+	table.Unlock()
+
+	// 有回调函数便执行回调
+	if addedItem != nil {
+		addedItem(&item)
+	}
+
+	// 如果我们没有设置任何心跳检查定时器或者找一个即将迫近的项目
+	if lifeSpan > 0 && (expDur == 0 || lifeSpan < expDur) {
+		table.expirationCheck()
+	}
+
+	return &item
+}
+
+// 从缓存中删除项
+func (table *CacheTable) Delete(key interface{}) (*CacheItem, error) {
+	table.RLock()
+	r, ok := table.items[key]
+	if !ok {
+		table.RUnlock()
+		return nil, errors.New(fmt.Sprintf("没有找到%s对应的记录", key))
+	}
+
+	// 取出要用到的东西，释放锁
+	aboutToDeleteItem := table.aboutToDeleteItem
+	table.RUnlock()
+
+	// 调用删除回调函数
+	if aboutToDeleteItem != nil {
+		aboutToDeleteItem(r)
+	}
+
+	r.RLock()
+	defer r.RUnlock()
+	if r.aboutToExpire != nil {
+		r.aboutToExpire(key)
+	}
+
+	table.Lock()
+	defer table.Unlock()
+	table.log("Deleting item with key", key, "created on", r.createdOn, "and hit", r.accessCount, "times from table", table.name)
+	delete(table.items, key)
+
+	return r, nil
+}
+
+//单纯的检查某个键是否存在
+func (table *CacheTable) Exists(key interface{}) bool {
+	table.RLock()
+	defer table.RUnlock()
+	_, ok := table.items[key]
+
+	return ok
+}
+
+//如果存在，返回false. 如果不存在,就去添加一个键，并且返回true
+func (table *CacheTable) NotFoundAdd(key interface{}, lifeSpan time.Duration, data interface{}) bool {
+	table.Lock()
+
+	if _, ok := table.items[key]; ok {
+		table.Unlock()
+		return false
+	}
+
+	item := CreateCacheItem(key, lifeSpan, data)
+	table.log("Adding item with key", key, "and lifespan of", lifeSpan, "to table", table.name)
+	table.items[key] = &item
+
+	// 取出需要的内容，释放锁
+	expDur := table.cleanupInterval
+	addedItem := table.addedItem
+	table.Unlock()
+
+	// 添加回调函数
+	if addedItem != nil {
+		addedItem(&item)
+	}
+
+	// 触发过期检查
+	if lifeSpan > 0 && (expDur == 0 || lifeSpan < expDur) {
+		table.expirationCheck()
+	}
+	return true
+}
+
+// Get an item from the cache and mark it to be kept alive. You can pass
+// additional arguments to your DataLoader callback function.
+//从缓存中返回一个被标记的并保持活性的值。你可以传附件的参数到DataLoader回调函数
+func (table *CacheTable) Value(key interface{}, args ...interface{}) (*CacheItem, error) {
+	table.RLock()
+	r, ok := table.items[key]
+	loadData := table.loadData
+	table.RUnlock()
+
+	if ok {
+		// 更新访问次数和访问时间
+		r.KeepAlive()
+		return r, nil
+	}
+
+	// 有加载数据的方式，就通过loadData函数去加载进来
+	if loadData != nil {
+		item := loadData(key, args...)
+		if item != nil {
+			table.Add(key, item.lifeSpan, item.data)
+			return item, nil
+		}
+
+		return nil, errors.New("无法加载到缓存值")
+	}
+
+	return nil, errors.New(fmt.Sprintf("没有找到%s对应的记录", key))
+}
+
+// 删除缓存表中的所有项目
+func (table *CacheTable) Flush() {
+	table.Lock()
+	defer table.Unlock()
+
+	table.log("Flushing table", table.name)
+
+	table.items = make(map[interface{}]*CacheItem)
+	table.cleanupInterval = 0
+	if table.cleanupTimer != nil {
+		table.cleanupTimer.Stop()
+	}
+}
+
+//辅助table中排序，统计的
+type CacheItemPair struct {
+	Key         interface{}
+	AccessCount int64
+}
+
+type CacheItemPairList []CacheItemPair
+
+func (p CacheItemPairList) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+func (p CacheItemPairList) Len() int           { return len(p) }
+func (p CacheItemPairList) Less(i, j int) bool { return p[i].AccessCount > p[j].AccessCount }
+
+// 返回缓存表中被访问最多的项目
+func (table *CacheTable) MostAccessed(count int64) []*CacheItem {
+	table.RLock()
+	defer table.RUnlock()
+
+	p := make(CacheItemPairList, len(table.items))
+	i := 0
+	for k, v := range table.items {
+		p[i] = CacheItemPair{k, v.accessCount}
+		i++
+	}
+	sort.Sort(p)
+
+	var r []*CacheItem
+	c := int64(0)
+	for _, v := range p {
+		if c >= count {
+			break
+		}
+
+		item, ok := table.items[v.Key]
+		if ok {
+			r = append(r, item)
+		}
+		c++
+	}
+
+	return r
+}
+
+
+// 打印日志
+func (table *CacheTable) log(v ...interface{}) {
+	if table.logger == nil {
+		fmt.Println(v...)
+		return
+	}
+
+	table.logger.Println(v...)
+}
+
+var (
+	cacheTableMap   = make(map[string]*CacheTable)
+	cacheTableMutex sync.RWMutex
+)
+
+//统一管理所有的缓存表，如果没有就返回一个新的。
+func Cache(table string) *CacheTable {
+	cacheTableMutex.RLock()
+	t, ok := cacheTableMap[table]
+	cacheTableMutex.RUnlock()
+
+	if !ok {
+		t = &CacheTable{
+			name:  table,
+			items: make(map[interface{}]*CacheItem),
+		}
+
+		cacheTableMutex.Lock()
+		cacheTableMap[table] = t
+		cacheTableMutex.Unlock()
+	}
+
+	return t
+}