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C# 针对特定的条件进行锁操作，不用lock，而是mutex - pig-tong
source link: https://www.cnblogs.com/bookobe/p/11229021.html
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C# 针对特定的条件进行锁操作，不用lock，而是mutex
背景：用户领取优惠券，同一个用户需要加锁验证是否已经领取，不同用户则可以同时领取。
上代码示例：
1、创建Person类
/// <summary>
/// Person类
/// </summary>
public class Person
{
/// <summary>
/// id
/// </summary>
public int Id { get; set; }
/// <summary>
/// 姓名
/// </summary>
public string Name { get; set; }
/// <summary>
/// 是否获得优惠券
/// </summary>
public bool IsGetCoupon { get; set; }
}
2.1、不加锁的方法(可能会出现重复领取的情况)
/// <summary>
/// 获取优惠券
/// </summary>
public static void GetCoupon(Person person)
{
Console.WriteLine("date:{0:yyyy-MM-dd HH:mm:ss},name:{1},前来领取优惠券", DateTime.Now, person.Name);
if (person.IsGetCoupon)
{
//假装业务处理
Thread.Sleep(1000);
Console.WriteLine("date:{0:yyyy-MM-dd HH:mm:ss},name:{1},已经领取，不可重复领取", DateTime.Now, person.Name);
}
else
{
//假装业务处理
Thread.Sleep(1000);
//领取
person.IsGetCoupon = true;
Console.WriteLine("date:{0:yyyy-MM-dd HH:mm:ss},name:{1},领取成功", DateTime.Now, person.Name);
}
}
2.2、加lock锁的方法，所有来领优惠券的人，都得排对领（也不好）
/// <summary>
/// Lock获取优惠券
/// </summary>
public static void LockGetCoupon(Person person)
{
Console.WriteLine("date:{0:yyyy-MM-dd HH:mm:ss},name:{1},前来领取优惠券", DateTime.Now, person.Name);
lock (LockObj)
{
//判断是否已经领取
if (person.IsGetCoupon)
{
//假装业务处理
Thread.Sleep(1000);
Console.WriteLine("date:{0:yyyy-MM-dd HH:mm:ss},name:{1},已经领取，不可重复领取", DateTime.Now, person.Name);
}
else
{
//假装业务处理
Thread.Sleep(1000);
//领取
person.IsGetCoupon = true;
Console.WriteLine("date:{0:yyyy-MM-dd HH:mm:ss},name:{1},领取成功", DateTime.Now, person.Name);
}
}
}
2.3、mutex锁，互斥锁，只有相同id的人，才会排对领取，不同id的人就可以同时领取
/// <summary>
/// Mutex，领取
/// </summary>
/// <param name="person"></param>
public static void MutexGetCoupon(Person person)
{
Console.WriteLine("date:{0:yyyy-MM-dd HH:mm:ss},name:{1},前来领取优惠券", DateTime.Now, person.Name);
using (var mutex = new Mutex(false, person.Id.ToString()))
{
try
{
if (mutex.WaitOne(-1, false))
{
//判断是否已经领取
if (person.IsGetCoupon)
{
//假装业务处理
Thread.Sleep(1000);
Console.WriteLine("date:{0:yyyy-MM-dd HH:mm:ss},name:{1},已经领取，不可重复领取", DateTime.Now, person.Name);
}
else
{
//假装业务处理
Thread.Sleep(1000);
//领取
person.IsGetCoupon = true;
Console.WriteLine("date:{0:yyyy-MM-dd HH:mm:ss},name:{1},领取成功", DateTime.Now, person.Name);
}
}
}
catch (Exception ex)
{
//TxtLogHelper.WriteLog(ex);
}
finally
{
mutex.ReleaseMutex();
}
}
}
}
3.1、开始测试(不加锁)
static void Main(string[] args)
{
//实例化三个人
Person p1 = new Person { Id = 24, Name = "Kobe" };
Person p2 = new Person { Id = 25, Name = "Rose" };
Person p3 = new Person { Id = 23, Name = "Lebl" };
//开启多线程、模拟三个人同时发起多次领取请求
for (int i = 0; i < 4; i++)
{
new Thread(() =>
{
GetCoupon(p1);
}).Start();
new Thread(() =>
{
GetCoupon(p2);
}).Start();
new Thread(() =>
{
GetCoupon(p3);
}).Start();
}
Console.ReadLine();
}
测试结果：每个人都重复领取
3.2、测试lock锁方法，
private static readonly object LockObj = new object();
static void Main(string[] args)
{
//实例化三个人
Person p1 = new Person { Id = 24, Name = "Kobe" };
Person p2 = new Person { Id = 25, Name = "Rose" };
Person p3 = new Person { Id = 23, Name = "Lebl" };
//开启多线程、模拟三个人同时发起多次领取请求
for (int i = 0; i < 4; i++)
{
new Thread(() =>
{
LockGetCoupon(p1);
}).Start();
new Thread(() =>
{
LockGetCoupon(p2);
}).Start();
new Thread(() =>
{
LockGetCoupon(p3);
}).Start();
}
Console.ReadLine();
}
测试结果：虽然避免了重复领取，但是每个人都的每个请求都要排对。如果用户量大的话，这种方式效率就太低了，所以不推荐。
3.3、测试mutex锁，互斥锁
static void Main(string[] args)
{
//实例化三个人
Person p1 = new Person { Id = 24, Name = "Kobe" };
Person p2 = new Person { Id = 25, Name = "Rose" };
Person p3 = new Person { Id = 23, Name = "Lebl" };
//开启多线程、模拟三个人同时发起多次领取请求
for (int i = 0; i < 4; i++)
{
new Thread(() =>
{
MutexGetCoupon(p1);
}).Start();
new Thread(() =>
{
MutexGetCoupon(p2);
}).Start();
new Thread(() =>
{
MutexGetCoupon(p3);
}).Start();
}
Console.ReadLine();
}
测试结果：既避免了重复领取，也避免了堵塞用户请求的情况。见下面截图，Kobe、Rose、Lebl是同时领取的优惠券，但是每个人的重复请求都在排对
总结：mutex锁，完美的解决了此类问题。
--------------------------------------------华丽的分割线 --------------------------------------------
感谢各位大佬提出的问题和建议，我确实没有考虑到这些问题。
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