ASP.NET Core中的对象池化技术详解
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); } } }
调用示例
因为设置了回收条件,所以只有名字为rjcql的对象才会被回收,所以每次调用都先把rjcql对象取出。
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