Hangfire 事务处理（工作单元）

Question

在下面的 .Net Framework 代码中，确保将 someEntity 对象插入到 db 中，然后执行 Publish 操作。但是，在 .Net Core 中我无法做到这一点。当我尝试运行这段代码时，会发生平台异常。

using (var transaction = new TransactionScope())
{
    SomeEntity someEntity = new SomeEntity();
    someEntity.Gui = Guid.NewGuid().ToString();

    _dataContext.SomeEntities.Add(someEntity);
    _dataContext.SaveChanges();

    _backgroundJobClient.Enqueue(() => PublishSomeEntityCreatedEvent(someEntity.Id)));

    transaction.Complete();
}

对于这种情况有什么好的解决方案吗？

注意：.Net Core 2.2 Console 应用，EntityFrameworkCore 2.1 和 Hangfire 1.6.21 用于测试

---

更新：整个堆栈跟踪

Hangfire.BackgroundJobClientException: Background job creation failed. See inner exception for details. ---> System.PlatformNotSupportedException: This platform
 does not support distributed transactions.
   at System.Transactions.Distributed.DistributedTransactionManager.GetDistributedTransactionFromTransmitterPropagationToken(Byte[] propagationToken)
   at System.Transactions.TransactionInterop.GetDistributedTransactionFromTransmitterPropagationToken(Byte[] propagationToken)
   at System.Transactions.TransactionStatePSPEOperation.PSPEPromote(InternalTransaction tx)
   at System.Transactions.TransactionStateDelegatedBase.EnterState(InternalTransaction tx)
   at System.Transactions.EnlistableStates.Promote(InternalTransaction tx)
   at System.Transactions.Transaction.Promote()
   at System.Transactions.TransactionInterop.ConvertToDistributedTransaction(Transaction transaction)
   at System.Transactions.TransactionInterop.GetExportCookie(Transaction transaction, Byte[] whereabouts)
   at System.Data.SqlClient.SqlInternalConnection.GetTransactionCookie(Transaction transaction, Byte[] whereAbouts)
   at System.Data.SqlClient.SqlInternalConnection.EnlistNonNull(Transaction tx)
   at System.Data.SqlClient.SqlInternalConnection.Enlist(Transaction tx)
   at System.Data.SqlClient.SqlInternalConnectionTds.Activate(Transaction transaction)
   at System.Data.ProviderBase.DbConnectionInternal.ActivateConnection(Transaction transaction)
   at System.Data.ProviderBase.DbConnectionPool.PrepareConnection(DbConnection owningObject, DbConnectionInternal obj, Transaction transaction)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.Open()
   at Hangfire.SqlServer.SqlServerStorage.CreateAndOpenConnection()
   at Hangfire.SqlServer.SqlServerStorage.UseConnection[T](DbConnection dedicatedConnection, Func`2 func)
   at Hangfire.SqlServer.SqlServerConnection.CreateExpiredJob(Job job, IDictionary`2 parameters, DateTime createdAt, TimeSpan expireIn)
   at Hangfire.Client.CoreBackgroundJobFactory.Create(CreateContext context)
   at Hangfire.Client.BackgroundJobFactory.<>c__DisplayClass7_0.<CreateWithFilters>b__0()
   at Hangfire.Client.BackgroundJobFactory.InvokeClientFilter(IClientFilter filter, CreatingContext preContext, Func`1 continuation)
   at Hangfire.Client.BackgroundJobFactory.<>c__DisplayClass7_1.<CreateWithFilters>b__2()
   at Hangfire.Client.BackgroundJobFactory.CreateWithFilters(CreateContext context, IEnumerable`1 filters)
   at Hangfire.Client.BackgroundJobFactory.Create(CreateContext context)
   at Hangfire.BackgroundJobClient.Create(Job job, IState state)
   --- End of inner exception stack trace ---
   at Hangfire.BackgroundJobClient.Create(Job job, IState state)
   at Hangfire.BackgroundJobClientExtensions.Create(IBackgroundJobClient client, Expression`1 methodCall, IState state)
   at Hangfire.BackgroundJobClientExtensions.Enqueue(IBackgroundJobClient client, Expression`1 methodCall)
   at TopShelf_Hangfire_NetCore.BusinessService.Execute(DateTime utcNow) in C:\Projects\Practices\TopShelf_Hangfire_NetCore\BusinessService.cs:line 31
   at TopShelf_Hangfire_NetCore.StartupService._timer_Elapsed(Object sender, ElapsedEventArgs e) in C:\Projects\Practices\TopShelf_Hangfire_NetCore\StartupService.cs:line 35

Answer 1

现在在使用 EntityFramework Core 3.0 或更高版本时可以使用。 这在 EFCore 2.x 中不起作用的原因是 EFCore 2.x 在不使用时没有关闭连接。相反，在释放上下文之前，DbConnection 一直保持打开状态。

此行为在 EF Core 3.0 中已更改：https://docs.microsoft.com/en-us/ef/core/what-is-new/ef-core-3.0/breaking-changes#database-connection-is-now-closed-if-not-used-anymore-before-the-transactionscope-has-been-completed

从 3.0 开始，EF Core 会在使用完连接后立即关闭它。 这支持您的方案，您希望在同一事务中加入 EfCore 和 Hangfire，而不升级到 MSDTC。

Answer 2

似乎正在启动分布式事务，.net 核心不支持 abd。

由于您要访问多个资源管理器（您的数据库和hangfire 的数据库），因此事务范围会尝试升级要分发的事务。

您可以将 hangfire 的 _backgroundJobClient.Enqueue() 带出范围，因此不会发生升级。

您必须找到另一种方法来确保执行这两个操作（数据库更新、hangfire enqueue）

编辑： 由于您无法进行交易，因此您必须设计服务以处理可能的故障情况。例如： 帐户服务将：

1. 将创建的持久化到db

2. 然后调用hangfire Enqueue

3. 记录hangfire作业是在同一用户db中创建的事实。

4. 用户服务必须轮询数据库，以查看是否创建了用户但未记录通知。

其他微服务，应该能够处理重复通知。

这样，如果创建了用户但没有发送通知，您的服务将重新发送（4）。

如果失败发生在 (2) 和 (3) 之间，接收服务将忽略重复请求