有花時間去研究masstransit的saga，英文水平不過關，始終無法實現上手他的程式碼編排的業務，遺憾。
本文通過rabbit和sqlserver實現下單，更新庫存，更新產品，模擬資料最終一致性。
專案結構如下,reportService可有可無，這裡就相當一個鏈條，只要兩節走通了後面可以接龍，本文有用到不省略。流程：orderservice=>eComm=>reportservice 。
下面先看看order的配置，通過控制器新增訂單同時釋出訂單資訊到order_exchange交換機，Key是"order.created,這樣就把訂單推送到了佇列，等到庫存服務獲取訂單去更新庫存。
// POST api/<OrderController>
[HttpPost]
public async Task Post([FromBody] OrderDetail orderDetail)
{
var id = await orderCreator.Create(orderDetail);
publisher.Publish(JsonConvert.SerializeObject(new OrderRequest {
OrderId = id,
ProductId = orderDetail.ProductId,
Quantity = orderDetail.Quantity
}), "order.created", null);
}
更新庫存的程式碼，然後再傳送訊息告訴order服務，這裡有哪個try包裹，如果這裡有失敗會觸發catch，傳送減庫存失敗的訊息。order服務消費到這條訊息就會執行相應的刪除訂單操作。程式碼如下：
using Ecomm.DataAccess;
using Ecomm.Models;
using Microsoft.Extensions.Hosting;
using Newtonsoft.Json;
using Plain.RabbitMQ;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
namespace Ecomm
{
public class OrderCreatedListener : IHostedService
{
private readonly IPublisher publisher;
private readonly ISubscriber subscriber;
private readonly IInventoryUpdator inventoryUpdator;
public OrderCreatedListener(IPublisher publisher, ISubscriber subscriber, IInventoryUpdator inventoryUpdator)
{
this.publisher = publisher;
this.subscriber = subscriber;
this.inventoryUpdator = inventoryUpdator;
}
public Task StartAsync(CancellationToken cancellationToken)
{
subscriber.Subscribe(Subscribe);
return Task.CompletedTask;
}
private bool Subscribe(string message, IDictionary<string, object> header)
{
var response = JsonConvert.DeserializeObject<OrderRequest>(message);
try
{
inventoryUpdator.Update(response.ProductId, response.Quantity).GetAwaiter().GetResult();
publisher.Publish(JsonConvert.SerializeObject(
new InventoryResponse { OrderId = response.OrderId, IsSuccess = true }
), "inventory.response", null);
}
catch (Exception)
{
publisher.Publish(JsonConvert.SerializeObject(
new InventoryResponse { OrderId = response.OrderId, IsSuccess = false }
), "inventory.response", null);
}
return true;
}
public Task StopAsync(CancellationToken cancellationToken)
{
return Task.CompletedTask;
}
}
}
using Ecomm.Models;
using Microsoft.Extensions.Hosting;
using Newtonsoft.Json;
using Plain.RabbitMQ;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
namespace OrderService
{
public class InventoryResponseListener : IHostedService
{
private readonly ISubscriber subscriber;
private readonly IOrderDeletor orderDeletor;
public InventoryResponseListener(ISubscriber subscriber, IOrderDeletor orderDeletor)
{
this.subscriber = subscriber;
this.orderDeletor = orderDeletor;
}
public Task StartAsync(CancellationToken cancellationToken)
{
subscriber.Subscribe(Subscribe);
return Task.CompletedTask;
}
private bool Subscribe(string message, IDictionary<string, object> header)
{
var response = JsonConvert.DeserializeObject<InventoryResponse>(message);
if (!response.IsSuccess)
{
orderDeletor.Delete(response.OrderId).GetAwaiter().GetResult();
}
return true;
}
public Task StopAsync(CancellationToken cancellationToken)
{
return Task.CompletedTask;
}
}
}
上面的程式碼是整個服務的核心業務，也很簡單就是佇列相互通訊相互確認操作是否順利，失敗就執行迴歸操作，而這裡我們都會寫好對應補償程式碼：
using Dapper; using System; using System.Collections.Generic; using System.Data.SqlClient; using System.Linq; using System.Threading.Tasks; namespace OrderService { public class OrderDeletor : IOrderDeletor { private readonly string connectionString; public OrderDeletor(string connectionString) { this.connectionString = connectionString; } public async Task Delete(int orderId) { using var connection = new SqlConnection(connectionString); connection.Open(); using var transaction = connection.BeginTransaction(); try { await connection.ExecuteAsync("DELETE FROM OrderDetail WHERE OrderId = @orderId", new { orderId }, transaction: transaction); await connection.ExecuteAsync("DELETE FROM [Order] WHERE Id = @orderId", new { orderId }, transaction: transaction); transaction.Commit(); } catch { transaction.Rollback(); } } } }
庫存服務裡有釋出產品的介面，這裡沒有做過多的處理，只是把產品新增放到佇列，供後面的ReportService服務獲取，該服務拿到後會執行產品數量扣除：
using Microsoft.Extensions.Hosting; using Newtonsoft.Json; using Plain.RabbitMQ; using System.Collections.Generic; using System.Linq; using System.Threading; using System.Threading.Tasks; namespace ReportService { public class ReportDataCollector : IHostedService { private const int DEFAULT_QUANTITY = 100; private readonly ISubscriber subscriber; private readonly IMemoryReportStorage memoryReportStorage; public ReportDataCollector(ISubscriber subscriber, IMemoryReportStorage memoryReportStorage) { this.subscriber = subscriber; this.memoryReportStorage = memoryReportStorage; } public Task StartAsync(CancellationToken cancellationToken) { subscriber.Subscribe(Subscribe); return Task.CompletedTask; } private bool Subscribe(string message, IDictionary<string, object> header) //private bool ProcessMessage(string message, IDictionary<string, object> header) { if (message.Contains("Product")) { var product = JsonConvert.DeserializeObject<Product>(message); if (memoryReportStorage.Get().Any(r => r.ProductName == product.ProductName)) { return true; } else { memoryReportStorage.Add(new Report { ProductName = product.ProductName, Count = DEFAULT_QUANTITY }); } } else { var order = JsonConvert.DeserializeObject<Order>(message); if(memoryReportStorage.Get().Any(r => r.ProductName == order.Name)) { memoryReportStorage.Get().First(r => r.ProductName == order.Name).Count -= order.Quantity; } else { memoryReportStorage.Add(new Report { ProductName = order.Name, Count = DEFAULT_QUANTITY - order.Quantity }); } } return true; } public Task StopAsync(CancellationToken cancellationToken) { return Task.CompletedTask; } } }
到這裡整個流程大概如此。只要理清楚了訂單和庫存更新這裡的業務，後面差不多一樣，可以無限遞迴。程式碼文末有連結供下載。
這裡有一個地方的程式碼如下,新增庫存的時候同時釋出訊息。假如新增完訂單後面崩掉了，這裡是個原子操作最佳。
[HttpPost]
public async Task Post([FromBody] OrderDetail orderDetail)
{
var id = await orderCreator.Create(orderDetail);
publisher.Publish(JsonConvert.SerializeObject(new OrderRequest {
OrderId = id,
ProductId = orderDetail.ProductId,
Quantity = orderDetail.Quantity
}), "order.created", null);
}
很遺憾masstransit的saga還沒有整明白，那就上cap，完成業務一致性。加了點cap程式碼因為之前是dapper，所以加了dbcontext和cap相關程式碼有點小亂。核心程式碼如下：
using DotNetCore.CAP;
using MediatR;
using OrderService.Command;
using System.Threading;
using Ecomm.Models;
using System.Collections.Generic;
namespace OrderService.Handler
{
public class InsertOrderDetailHandler : IRequestHandler<InsertOrderDetailCommand, InsertOrderDetailModel>
{
private readonly OrderDbContext context;
private readonly ICapPublisher cap;
public InsertOrderDetailHandler(OrderDbContext context, ICapPublisher cap)
{
this.context = context;
this.cap = cap;
}
public async System.Threading.Tasks.Task<InsertOrderDetailModel> Handle(InsertOrderDetailCommand request, CancellationToken cancellationToken)
{
using(var trans =context.Database.BeginTransaction(cap))
{
var order = context.Orders.Add(new Order
{
UpdatedTime = System.DateTime.Today,
UserId = request.UserId,
UserName = request.UserName
});
var orderDetail = context.OrderDetails.Add(new OrderDetail
{
OrderId = order.Entity.Id,
ProductId = request.ProductId,
Quantity = request.Quantity,
ProductName = request.ProductName,
});
context.SaveChanges();
cap.Publish<OrderRequest>("order.created", new OrderRequest
{
OrderId = order.Entity.Id,
ProductId = orderDetail.Entity.ProductId,
Quantity = orderDetail.Entity.Quantity
}, new Dictionary<string,string>()) ;
trans.Commit();
return new InsertOrderDetailModel { OrderDetailid = orderDetail.Entity.Id, OrderId = order.Entity.Id, Success = true };
}
}
}
}
到這裡差不多要結束了，這裡的程式碼都可以除錯執行的。因為加了cap，order服務有兩套rabbitmq的配置，有冗餘，而且有點坑。除錯的時候注意，Plain.RabbitMQ支援的交換機不是持久化的，而cap是持久化的，所以有點不相容。第一次執行可以先確保Plain.RabbitMQ正常，再刪掉交換機，cap跑起來了再建持久化交換機，這樣cap訊息就會被rabbitmq接收，後面就會被庫存服務消費。因為我這裡cap不會自動繫結佇列，Plain.RabbitMQ是可以的。所以需要新建交換機後再繫結佇列。而且這裡佇列以Plain.RabbitMQ生成的名字來繫結。要不然又可能會除錯踩坑無法出坑。 用cap不注意你連訊息佇列都看不到，看到了佇列也看不到消費資料，這點不知道是我不會還是cap有什麼難的配置。結束。。。
上例專案demo:
liuzhixin405/SimpleOrders_Next (github.com)
超簡單微服務demo