缓存cache(擦车)
<p>第一次打仗到Cache的时间,是在WebForm中,第一次打仗,我就再也没能忘记,cache(擦车,的拼音)</p><p>客户端欣赏器缓存https://blog.csdn.net/y874961524/article/details/61419716</p>
<p>CDN缓存原理https://www.cnblogs.com/shijingxiang/articles/5179032.html</p>
<p>阿里云CDN开启设置https://jingyan.baidu.com/article/948f5924f1d642d80ff5f980.html</p>
<p>有句话叫做,系统性能优化的第一步,就是使用缓存,所以,缓存真的很重要</p>
<p>缓存:</p>
<p> 实际上是一种结果&目的,就是获取数据点时间,第一次获取之后找个地方存起来,反面直接用,这样一来可以提拔反面每次获取数据的效率。读取设置文件的时间把信息放在静态字段,这个就是缓存。缓存是无处不在的。</p>
<p><div align="center"></div></p>
<p> </p>
<p> </p>
<p>我们来哀求一个网站,打开开辟职员工具</p>
<p><div align="center"></div></p>
<p> </p>
<p> </p>
<p> 客户端缓存的利益:</p>
<p> 1、紧缩网络路径,加速相应速度</p>
<p> 2、减少哀求,低落服务器压力</p>
<p>欣赏器缓存毕竟是怎么做到的?</p>
<p> 打开一个网页,欣赏器-----哀求---服务器---处理哀求会发相应------欣赏器展示</p>
<p> Http协议,数据传输的格式(协议,就像是两人交换,都用什么语言)</p>
<p> 信息是否缓存,一定是服务器控制的。ResponseHeader--Cache---Control来指定下缓存计谋,欣赏器看到了这个,就去存储一下。</p>
<p>第一次哀求服务器:</p>
<p><div align="center"></div></p>
<p> </p>
<p> </p>
<p> 再一次哀求服务器</p>
<p> <div align="center"></div></p>
<p> </p>
<p> </p>
<p> DNS是互联网的第一跳,DNS缓存就是CDN,内容分发网络,CDN就是加速缓存的</p>
<p>没有效CDN的哀求:</p>
<p><div align="center"></div></p>
<p> </p>
<p> </p>
<p> 使用了CDN缓存</p>
<p><div align="center"></div></p>
<p> </p>
<p> </p>
<p> 反向署理:</p>
<p> 1、隔离网络,保护服务器(节省公共IP)</p>
<p> 2、网络加速,反向署理双网卡</p>
<p> 3、负载平衡</p>
<p> 4、缓存(跟CDN,也是辨认一下header,压缩到一个物理路径/内存)</p>
<p> 为什么叫反向署理?因为他就是一个署理,一样平常的署理,是客户端和服务器之间,有一个署理,去做处理的。但是这个署理是安装在服务器端的。</p>
<p><div align="center"></div></p>
<p> </p>
<p> </p>
<p> </p>
<p>几种缓存套路相同,但是位置不同,影响的范围也不同。</p>
<p> 客户端缓存:只影响当前用户</p>
<p> CDN缓存:针对一批用户</p>
<p> 反向署理缓存:针对全部用户。</p>
<p> 客户端缓存,存在内存或者硬盘,下次直接用。Cookie,存在内存或者硬盘,欣赏器每次哀求服务器都会带上的信息。</p>
<p>什么时间用缓存?</p>
<p> 1、重复哀求,100人访问首页,每个人其实做的都一样,不就是重复</p>
<p> 2、耗时好资源</p>
<p> 3、结果没变的</p>
<p>下面有一个第三方数据存储和获取的地方:</p>
/// <summary>
/// 第三方数据存储和获取的地方
/// </summary>
public class CustomCache
{
/// <summary>
/// private:私有一下数据容器,安全
/// static:不被GC
/// 字典:读写效率高
/// </summary>
private static Dictionary<string, object> CustomCacheDictionary = new Dictionary<string, object>();
public static void Add(string key, object oVaule)
{
CustomCacheDictionary.Add(key, oVaule);
}
/// <summary>
/// 要求在Get前做Exists检测
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="key"></param>
/// <returns></returns>
public static T Get<T>(string key)
{
return (T)CustomCacheDictionary;
}
public static bool Exists(string key)
{
return CustomCacheDictionary.ContainsKey(key);
}
public static T GetT<T>(string key, Func<T> func)
{
T t = default(T);
if (!CustomCache.Exists(key))
{
t = func.Invoke();
CustomCache.Add(key, t);
}
else
{
t = CustomCache.Get<T>(key);
}
return t;
}
}
<p>存取数据的唯一标识:1 唯一的2 能重现</p>
for (int i = 0; i < 5; i++)
{
Console.WriteLine($"获取{nameof(DBHelper)} {i}次 {DateTime.Now.ToString("yyyyMMdd HHmmss.fff")}");
//List<Program> programList = DBHelper.Query<Program>(123);
List<Program> programList = null;
string key = $"{nameof(DBHelper)}_Query_{123}";
//存取数据的唯一标识:1 唯一的2 能重现
//if (!CustomCache.Exists(key))
//{
// programList = DBHelper.Query<Program>(123);
// CustomCache.Add(key, programList);
//}
//else
//{
// programList = CustomCache.Get<List<Program>>(key);
//}
programList = CustomCache.GetT<List<Program>>(key, () => DBHelper.Query<Program>(123));
}
<p> </p>
/// <summary>
/// 数据库查询
/// </summary>
public class DBHelper
{
/// <summary>
/// 1 耗时耗资源
/// 2 参数固定时,结果稳定
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="index"></param>
/// <returns></returns>
public static List<T> Query<T>(int index)
{
Console.WriteLine("This is {0} Query", typeof(DBHelper));
long lResult = 0;
for (int i = index; i < 1000000000; i++)
{
lResult += i;
}
List<T> tList = new List<T>();
for (int i = 0; i < index % 3; i++)
{
tList.Add(default(T));
}
return tList;
}
}
<p> 缓存优化性能,焦点就是结果重用,下次哀求照旧上一次的结果。如果数据库中有变化,岂不是用了一个错误的数据?是的,缓存是难免的,缓存难免会有脏数据,固然了,我们也会分门别类的去只管减少脏数据。</p>
<p> 用户--脚色--菜单,用户权限查的多+比力耗资源+相对稳固,非常得当缓存,缓存方式应该是用户id为key,菜单列表作为value。</p>
string name = "bingle";
List<string> menu = new List<string>();
if (!CustomCache.Exists(name))
{
menu = new List<string>() { "123", "125553", "143", "123456" };
CustomCache.Add(name, menu);
}
else
{
menu = CustomCache.Get<List<string>>(name);
}
<p>如果bingle的权限变化了,缓存应该失效。数据更新影响单挑缓存,常规做法是Remove而不是更新,因为缓存只是用来提拔效率的,而不是数据生存的,因此不必要更新,只必要删除就好,如果真的下次用上了,到时间再去初始化。</p>
CustomCache类增长删除缓存的方法:<br />
public static void Remove(string key)
{
CustomCacheDictionary.Remove(key);
}
string name = "bingle";
CustomCache.Remove(name);
List<string> menu = new List<string>();
if (!CustomCache.Exists(name))
{
menu = new List<string>() { "123", "125553", "143" };
CustomCache.Add(name, menu);
}
else
{
menu = CustomCache.Get<List<string>>(name);
}
<p>删除了某个菜单,影响了一大批用户。根据菜单--昭觉寺---找用户---每一个拼装key然后去Remove(最准确)。但是这种方式不可,为了缓存增长数据库的任务,最大的问题是数据量的问题,缓存是二八原则,只有20%的热门用户才缓存,这样做的本钱太高。</p>
<p>可以选择加上一个RemoveAll的方法</p>
public static void RemoveAll()
{
CustomCacheDictionary.Clear();
}
<p>或者,菜单删除了,能不能只影响一部门的缓存数据呢?</p>
<p> 1、添加缓存时,key带上规则,比如权限包罗_menu_</p>
<p> 2、整理时,就只删除key含_menu_的</p>
/// <summary>
/// 按条件删除
/// </summary>
/// <param name="func"></param>
public static void RemoveCondition(Func<string, bool> func)
{
List<string> keyList = new List<string>();
lock (CustomCache_Lock)
foreach (var key in CustomCacheDictionary.Keys)
{
if (func.Invoke(key))
{
keyList.Add(key);
}
}
keyList.ForEach(s => Remove(s));
}
<p>第三方修改了数据,缓存并不知道,这个就没办法了</p>
<p> a 可以调用接口整理缓存,b系统修改数据,调用c西永通知下缓存更新,b就只能容忍了,容忍脏数据,但是可以加上时间限制,减少影响时间。</p>
<p>时间,逾期计谋:</p>
<p> 永世有效----现在就是</p>
<p> 绝对逾期:</p>
<p> 有个时间点,高出就逾期了</p>
<p> 滑动逾期:</p>
<p> 多久之后逾期,如果期间更新/查询/查抄存在,就再次延长多久。</p>
/// <summary>
/// 自动整理
/// </summary>
static CustomCache()
{
Task.Run(() =>
{
while (true)
{
try
{
List<string> keyList = new List<string>();
lock (CustomCache_Lock)
{
foreach (var key in CustomCacheDictionary.Keys)
{
DataModel model = (DataModel)CustomCacheDictionary;
if (model.ObsloteType != ObsloteType.Never && model.DeadLine < DateTime.Now)
{
keyList.Add(key);
}
}
keyList.ForEach(s => Remove(s));
}
Thread.Sleep(1000 * 60 * 10);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
continue;
}
}
});
}
<p>多线程问题:</p>
List<Task> taskList = new List<Task>();
for (int i = 0; i < 110000; i++)
{
int k = i;
taskList.Add(Task.Run(() => CustomCache.Add($"TestKey_{k}", $"TestValue_{k}", 10)));
}
for (int i = 0; i < 100; i++)
{
int k = i;
taskList.Add(Task.Run(() => CustomCache.Remove($"TestKey_{k}")));
}
for (int i = 0; i < 100; i++)
{
int k = i;
taskList.Add(Task.Run(() => CustomCache.Exists($"TestKey_{k}")));
}
//Thread.Sleep(10*1000);
Task.WaitAll(taskList.ToArray());
<p>多线程操作非现场安全的容器,会造成冲突</p>
<p> 1、线程安全容器ConcurrentDictionary</p>
<p> 2、用lock---Add/Remove/遍历,可以解决问题,但是性能呢?</p>
<p> 怎么低落影响,提拔性能呢?多个数据容器,多个锁,容器之间可以并发</p>
<p>为相识决多线程问题,CustomCache 类最终修改成如下:</p>
<div align="center"></div><div align="center"></div>
public class CustomCache
{
//ConcurrentDictionary
private static readonly object CustomCache_Lock = new object();
/// <summary>
/// 自动整理
/// </summary>
static CustomCache()
{
Task.Run(() =>
{
while (true)
{
try
{
List<string> keyList = new List<string>();
lock (CustomCache_Lock)
{
foreach (var key in CustomCacheDictionary.Keys)
{
DataModel model = (DataModel)CustomCacheDictionary;
if (model.ObsloteType != ObsloteType.Never && model.DeadLine < DateTime.Now)
{
keyList.Add(key);
}
}
keyList.ForEach(s => Remove(s));
}
Thread.Sleep(1000 * 60 * 10);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
continue;
}
}
});
}
/// <summary>
/// private:私有一下数据容器,安全
/// static:不被GC
/// 字典:读写效率高
/// </summary>
//private static Dictionary<string, object> CustomCacheDictionary = new Dictionary<string, object>();
private static Dictionary<string, object> CustomCacheDictionary = new Dictionary<string, object>();
public static void Add(string key, object oVaule)
{
lock (CustomCache_Lock)
CustomCacheDictionary.Add(key, new DataModel()
{
Value = oVaule,
ObsloteType = ObsloteType.Never,
});
}
/// <summary>
/// 绝对逾期
/// </summary>
/// <param name="key"></param>
/// <param name="oVaule"></param>
/// <param name="timeOutSecond"></param>
public static void Add(string key, object oVaule, int timeOutSecond)
{
lock (CustomCache_Lock)
CustomCacheDictionary.Add(key, new DataModel()
{
Value = oVaule,
ObsloteType = ObsloteType.Absolutely,
DeadLine = DateTime.Now.AddSeconds(timeOutSecond)
});
}
/// <summary>
/// 相对逾期
/// </summary>
/// <param name="key"></param>
/// <param name="oVaule"></param>
/// <param name="duration"></param>
public static void Add(string key, object oVaule, TimeSpan duration)
{
lock (CustomCache_Lock)
CustomCacheDictionary.Add(key, new DataModel()
{
Value = oVaule,
ObsloteType = ObsloteType.Relative,
DeadLine = DateTime.Now.Add(duration),
Duration = duration
});
}
/// <summary>
/// 要求在Get前做Exists检测
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="key"></param>
/// <returns></returns>
public static T Get<T>(string key)
{
return (T)(((DataModel)CustomCacheDictionary).Value);
}
/// <summary>
/// 被动整理,哀求了数据,才能整理
/// </summary>
/// <param name="key"></param>
/// <returns></returns>
public static bool Exists(string key)
{
if (CustomCacheDictionary.ContainsKey(key))
{
DataModel model = (DataModel)CustomCacheDictionary;
if (model.ObsloteType == ObsloteType.Never)
{
return true;
}
else if (model.DeadLine < DateTime.Now)//现在已经高出你的末了时间
{
lock (CustomCache_Lock)
CustomCacheDictionary.Remove(key);
return false;
}
else
{
if (model.ObsloteType == ObsloteType.Relative)//没有逾期&是滑动 所以要更新
{
model.DeadLine = DateTime.Now.Add(model.Duration);
}
return true;
}
}
else
{
return false;
}
}
/// <summary>
/// 删除key
/// </summary>
/// <param name="key"></param>
public static void Remove(string key)
{
lock (CustomCache_Lock)
CustomCacheDictionary.Remove(key);
}
public static void RemoveAll()
{
lock (CustomCache_Lock)
CustomCacheDictionary.Clear();
}
/// <summary>
/// 按条件删除
/// </summary>
/// <param name="func"></param>
public static void RemoveCondition(Func<string, bool> func)
{
List<string> keyList = new List<string>();
lock (CustomCache_Lock)
foreach (var key in CustomCacheDictionary.Keys)
{
if (func.Invoke(key))
{
keyList.Add(key);
}
}
keyList.ForEach(s => Remove(s));
}
public static T GetT<T>(string key, Func<T> func)
{
T t = default(T);
if (!CustomCache.Exists(key))
{
t = func.Invoke();
CustomCache.Add(key, t);
}
else
{
t = CustomCache.Get<T>(key);
}
return t;
}
}
/// <summary>
/// 缓存的信息
/// </summary>
internal class DataModel
{
public object Value { get; set; }
public ObsloteType ObsloteType { get; set; }
public DateTime DeadLine { get; set; }
public TimeSpan Duration { get; set; }
//数据整理后出发事件
public event Action DataClearEvent;
}
public enum ObsloteType
{
Never,
Absolutely,
Relative
}
View Code
<div align="center"></div><div align="center"></div>
public class CustomCacheNew
{
//动态初始化多个容器和多个锁
private static int CPUNumer = 0;//获取系统的CPU数
private static List<Dictionary<string, object>> DictionaryList = new List<Dictionary<string, object>>();
private static List<object> LockList = new List<object>();
static CustomCacheNew()
{
CPUNumer = 4;
for (int i = 0; i < CPUNumer; i++)
{
DictionaryList.Add(new Dictionary<string, object>());
LockList.Add(new object());
}
Task.Run(() =>
{
while (true)
{
Thread.Sleep(1000 * 60 * 10);
try
{
for (int i = 0; i < CPUNumer; i++)
{
List<string> keyList = new List<string>();
lock (LockList)//减少锁的影响范围
{
foreach (var key in DictionaryList.Keys)
{
DataModel model = (DataModel)DictionaryList;
if (model.ObsloteType != ObsloteType.Never && model.DeadLine < DateTime.Now)
{
keyList.Add(key);
}
}
keyList.ForEach(s => DictionaryList.Remove(s));
}
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
continue;
}
}
});
}
View Code
<p>缓存毕竟那里用?满足哪些特点得当用缓存?</p>
<p> 1、访问频仍</p>
<p> 2、耗时耗资源</p>
<p> 3、相对稳固</p>
<p> 4、体积不那么大的</p>
<p> 不是说严酷满足,详细的还要看情况,存一次能查三次,就值得缓存(大型想换标准)</p>
<p> 下面应该用缓存</p>
<p> 1、字典数据</p>
<p><em id="__mceDel"> </em>2、省市区<br /> 3、设置文件<br /> 4、网站公告信息<br /> 5、部门权限,菜单权限<br /> 6、热搜<br /> 7、种别列表/产物列表<br /> 8、用户,其实Session也是缓存的一种表现</p>
<p> 股票信息代价/彩票开奖信息,这些不能用缓存,即时性要求很高。图片/视频,这些也不可,太大了。商品评论,这个可以用缓存的,虽然评论汇编,但是这个不重要,我们不一定非要看到最新的,而且第一页一样平常稳定。</p>
<p> 可以测试下CustomCache的性能,十万/百万/万万插入/获取/删除的性能。</p>
<br /><br />
<p> </p><br><br/><br/><br/><br/><br/>来源:<a href="https://www.cnblogs.com/taotaozhuanyong/p/11565162.html" target="_blank">https://www.cnblogs.com/taotaozhuanyong/p/11565162.html</a>
页:
[1]