using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using NewLife.Log;
using NewLife.Threading;
namespace XCode.Cache
{
/// <summary>实体缓存</summary>
/// <remarks>
/// 第一次读取缓存的时候，同步从数据库读取，这样子手上有一份数据。
/// 以后更新，都开异步线程去读取，而当前马上返回，让大家继续用着旧数据，这么做性能非常好。
/// </remarks>
/// <typeparam name="TEntity">实体类型</typeparam>
[DisplayName("实体缓存")]
public class EntityCache<TEntity> : CacheBase<TEntity>, IEntityCache where TEntity : Entity<TEntity>, new()
{
#region 基础属性
/// <summary>缓存过期时间</summary>
DateTime ExpiredTime { get; set; } = DateTime.Now.AddHours(-1);
/// <summary>缓存更新次数</summary>
private Int64 Times { get; set; }
/// <summary>过期时间。单位是秒，默认60秒</summary>
public Int32 Expire { get; set; }
/// <summary>填充数据的方法</summary>
public Func<IList<TEntity>> FillListMethod { get; set; } = Entity<TEntity>.FindAll;
/// <summary>是否等待第一次查询。如果不等待，第一次返回空集合。默认true</summary>
public Boolean WaitFirst { get; set; } = true;
/// <summary>是否在使用缓存，在不触发缓存动作的情况下检查是否有使用缓存</summary>
internal Boolean Using { get; private set; }
#endregion
#region 构造
/// <summary>实例化实体缓存</summary>
public EntityCache()
{
var exp = Setting.Current.EntityCacheExpire;
if (exp <= 0) exp = 60;
Expire = exp;
}
#endregion
#region 缓存核心
private IList<TEntity> _Entities = new List<TEntity>();
/// <summary>实体集合。无数据返回空集合而不是null</summary>
public IList<TEntity> Entities
{
get
{
CheckCache();
return _Entities;
}
}
void CheckCache()
{
// 更新统计信息
CheckShowStatics(ref Total, ShowStatics);
var sec = (TimerX.Now - ExpiredTime).TotalSeconds;
if (sec < 0)
{
Interlocked.Increment(ref Success);
return;
}
/*
* 来到这里，都是缓存超时的线程
* 1，第一次请求，还没有缓存数据，需要等待首次数据
* WaitFirst 加锁等待
* !WaitFirst 跳过等待
* 2，缓存过期，开个异步更新，继续走
*/
if (Times == 0)
{
if (WaitFirst)
{
lock (this)
{
if (Times == 0) UpdateCache("第一次");
}
}
else
{
if (Monitor.TryEnter(this, 5000))
{
try
{
if (Times == 0) UpdateCache("第一次");
}
finally
{
Monitor.Exit(this);
}
}
}
}
else
UpdateCacheAsync("过期{0:n0}秒".F(sec));
// 只要访问了实体缓存数据集合，就认为是使用了实体缓存，允许更新缓存数据期间向缓存集合添删数据
Using = true;
}
/// <summary>检索与指定谓词定义的条件匹配的所有元素。</summary>
/// <param name="match">条件</param>
/// <returns></returns>
public TEntity Find(Predicate<TEntity> match)
{
var list = Entities;
if (list is List<TEntity> list2) return list2.Find(match);
return list.FirstOrDefault(e => match(e));
}
/// <summary>检索与指定谓词定义的条件匹配的所有元素。</summary>
/// <param name="match">条件</param>
/// <returns></returns>
public IList<TEntity> FindAll(Predicate<TEntity> match)
{
var list = Entities;
if (list is List<TEntity> list2) return list2.FindAll(match);
return list.Where(e => match(e)).ToList();
}
#endregion
#region 缓存操作
private volatile Int32 _updating;
void UpdateCacheAsync(String reason)
{
// 控制只有一个线程能更新
if (Interlocked.CompareExchange(ref _updating, 1, 0) != 0) return;
ThreadPoolX.QueueUserWorkItem(() => UpdateCache(reason));
}
void UpdateCache(String reason)
{
Interlocked.Increment(ref _updating);
// 这里直接计算有效期，避免每次判断缓存有效期时进行的时间相加而带来的性能损耗
// 设置时间放在获取缓存之前，让其它线程不要空等
if (Times > 0) ExpiredTime = TimerX.Now.AddSeconds(Expire);
WriteLog("更新{0}（第{2}次） 原因：{1}", ToString(), reason, Times + 1);
try
{
_Entities = Invoke<Object, IList<TEntity>>(s => FillListMethod(), null);
}
catch (Exception ex)
{
XTrace.WriteLine($"[{TableName}/{ConnName}]" + ex.GetTrue());
}
finally
{
_updating = 0;
}
Times++;
ExpiredTime = TimerX.Now.AddSeconds(Expire);
WriteLog("完成{0}[{1}]（第{2}次）", ToString(), _Entities.Count, Times);
}
/// <summary>清除缓存</summary>
public void Clear(String reason)
{
if (!Using) return;
// 直接执行异步更新，明明白白，确保任何情况下数据最新，并且不影响其它任务的性能
UpdateCacheAsync(reason);
}
private IEntityOperate Operate = Entity<TEntity>.Meta.Factory;
internal void Add(TEntity entity)
{
if (!Using) return;
var es = _Entities;
lock (es)
{
es.Add(entity);
}
}
internal TEntity Remove(TEntity entity)
{
if (!Using) return null;
var es = _Entities;
var fi = Operate.Unique;
if (fi == null) return null;
var e = es.Find(x => x == entity);
if (e == null)
{
var v = entity[fi.Name];
e = es.Find(x => Equals(x[fi.Name], v));
}
if (e == null) return null;
//if (e != entity) e.CopyFrom(entity);
// 更新实体缓存时，不做拷贝，避免产生脏数据，如果恰巧又使用单对象缓存，那会导致自动保存
lock (es)
{
es.Remove(e);
}
return e;
}
internal TEntity Update(TEntity entity)
{
if (!Using) return null;
var rs = Remove(entity);
Add(entity);
return rs;
}
#endregion
#region 统计
/// <summary>总次数</summary>
public Int32 Total;
/// <summary>命中</summary>
public Int32 Success;
/// <summary>显示统计信息</summary>
public void ShowStatics()
{
if (Total > 0)
{
var sb = new StringBuilder();
var type = GetType();
var name = "{2}<{0}>({1:n0})".F(typeof(TEntity).Name, Entities.Count, type.GetDisplayName() ?? type.Name);
sb.AppendFormat("{0,-24}", name);
sb.AppendFormat("总次数{0,11:n0}", Total);
if (Success > 0) sb.AppendFormat("，命中{0,11:n0}（{1,6:P02}）", Success, (Double)Success / Total);
sb.AppendFormat("\t[{0}]", typeof(TEntity).FullName);
XTrace.WriteLine(sb.ToString());
}
}
#endregion
#region IEntityCache 成员
IList<IEntity> IEntityCache.Entities { get { return new List<IEntity>(Entities); } }
#endregion
#region 辅助
internal EntityCache<TEntity> CopySettingFrom(EntityCache<TEntity> ec)
{
Expire = ec.Expire;
FillListMethod = ec.FillListMethod;
return this;
}
/// <summary>输出名称</summary>
/// <returns></returns>
public override String ToString()
{
var type = GetType();
return "{0}<{1}>".F(type.GetDisplayName() ?? type.Name, typeof(TEntity).Name);
}
#endregion
}
}
|