ASP.NET Core中的对象池化技术详解_Asp.net

写在前面

microsoft.extensions.objectpool 是 asp.net core 基础结构的一部分，当对象的初始化成本较高，并且可能被频繁使用时，才适合采用对象池技术；被objectpool管理的对象不会进入垃圾回收，使用时通过由实例对象实现的get()方法，从对象池中借出对象，用完之后调用return(t obj)方法，将对象还回去。也可以在return(t obj)方法中设置判断条件，仅允许特定的对象进入对象池。

通过nuget 获取 microsoft.extensions.objectpool 类库

代码实现

using microsoft.extensions.dependencyinjection.extensions;
using microsoft.extensions.objectpool;
using system.security.cryptography;
using system.text;
 
var builder = webapplication.createbuilder(args);
 
// defaultpooledobjectpolicy: 默认的策略，继承抽象类pooledobjectpolicy
builder.services.tryaddsingleton<objectpoolprovider, defaultobjectpoolprovider>();
 
builder.services.tryaddsingleton<objectpool<reusablebuffer>>(serviceprovider =>
{
    var provider = serviceprovider.getrequiredservice<objectpoolprovider>();
    var policy = new defaultpooledobjectpolicy<reusablebuffer>();
    return provider.create(policy);
});
 
builder.services.tryaddsingleton<objectpool<person>>(serviceprovider => {
    var provider = serviceprovider.getrequiredservice<objectpoolprovider>();
    var policy = new personpoolpolicy();
    return provider.create(policy);
});
 
builder.services.tryaddsingleton<objectpool<stringbuilder>>(serviceprovider =>
{
    var provider = serviceprovider.getrequiredservice<objectpoolprovider>();
    var policy = new stringbuilderpooledobjectpolicy();
    return provider.create(policy);
});
 
var app = builder.build();
 
// config middleware
app.usemiddleware<birthdaymiddleware>();
 
app.mapget("/", () => "hello rjcql!");
 
// return the sha256 hash of a word 
http://localhost:5128/hash/xxxx
app.mapget("/hash/{word}", (string word, objectpool<reusablebuffer> bufferpool) =>
{
 
    var buffer = bufferpool.get();
    try
    {
        // set the buffer data to the ascii values of a word
        for (var i = 0; i < word.length; i++)
        {
            buffer.data[i] = (byte)word[i];
        }
 
        span<byte> hash = stackalloc byte[32];
        sha256.hashdata(buffer.data.asspan(0, word.length), hash);
        return "hash: " + convert.tohexstring(hash);
    }
    finally
    {
        // data is automatically reset because this type implemented iresettable
        bufferpool.return(buffer);
    }
});
 
app.mapget("/create/{name}", (string name, objectpool<person> personpool) =>
{
    var person = personpool.get();
    try
    {
        person.id = guid.newguid().tostring("n");
        var lastname = person.name; // 这个是上一个对象的值
        person.name = name;
        return $"{person.id}:{person.name}, {lastname}";
    }
    finally
    {
        // 根据条件回收
        personpool.return(person);
    }
});
 
app.run();
 
public class reusablebuffer : iresettable
{
    public byte[] data { get; } = new byte[1024 * 1024]; // 1 mb
 
    public bool tryreset()
    {
        array.clear(data);
        return true;
    }
}
 
public class person
{
    public string id { get; set; }
 
    public string name { get; set; }
}
 
public class personpoolpolicy : pooledobjectpolicy<person>
{
    public override person create()
    {
        return new person { id = "", name = "rjcql" };
    }
 
    public override bool return(person p)
    {
        if (p.name != "rjcql")
        {
            // 不允许其他名称的对象放入对象池
            return false;
        }
        return true;
    }
}
 
/// <summary>
/// 创建中间件
/// </summary>
public class birthdaymiddleware
{
    private readonly requestdelegate _next;
 
    public birthdaymiddleware(requestdelegate next)
    {
        _next = next;
    }
 
    public async task invokeasync(httpcontext context, objectpool<stringbuilder> builderpool)
    {
        var stringbuilder = builderpool.get();
        try
        {
            stringbuilder.append("hi");
            // 在中间干点啥别的
            // await context.response.writeasync(stringbuilder.tostring());
            await _next.invoke(context);
        }
        finally // 即使出错也要保证归还对象
        {
            builderpool.return(stringbuilder);
        }
    }
}