【发布时间】：2020-06-26 15:14:34
【问题描述】：
我的服务器使用 MySqlConnector 并与 AWS 上的 MySQL 数据库通信。我在 MySQL 中存储了 5 分钟的 API 计数器块。这些 API 计数器随着每次 API 调用而递增，并由 ConcurrentDictionary 代码处理（这似乎不是问题）。这行代码最近引发了一个异常，它是通过 MySqlConnector 访问 MySQL 数据库表的 linq 查询的一部分：
await _context.ApiCounts.Where(c => c.ApiName == apiName && c.StartTime >= startTime).ToListAsync();
我以前从未见过这条线失败，但突然我的一台服务器开始在上面的线中抛出以下异常：
InvalidOperationException: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct.
at System.ThrowHelper.ThrowInvalidOperationException_ConcurrentOperationsNotSupported
at System.Collections.Generic.Dictionary`2.FindEntry
at System.Collections.Generic.Dictionary`2.TryGetValue
at Remotion.Linq.Parsing.Structure.NodeTypeProviders.MethodInfoBasedNodeTypeRegistry.GetNodeType
at Remotion.Linq.Parsing.Structure.NodeTypeProviders.MethodInfoBasedNodeTypeRegistry.IsRegistered
at System.Linq.Enumerable.Any
at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.GetQueryOperatorExpression
at Remotion.Linq.Parsing.ExpressionVisitors.SubQueryFindingExpressionVisitor.Visit
at System.Linq.Expressions.ExpressionVisitor.VisitBinary
at System.Linq.Expressions.BinaryExpression.Accept
at System.Linq.Expressions.ExpressionVisitor.VisitBinary
at System.Linq.Expressions.BinaryExpression.Accept
at System.Linq.Expressions.ExpressionVisitor.VisitLambda
at System.Linq.Expressions.Expression`1.Accept
at System.Linq.Enumerable+SelectListPartitionIterator`2.ToArray
at System.Linq.Enumerable.ToArray
at Remotion.Linq.Parsing.Structure.MethodCallExpressionParser.Parse
at Remotion.Linq.Parsing.Structure.ExpressionTreeParser.ParseMethodCallExpression
at Remotion.Linq.Parsing.Structure.QueryParser.GetParsedQuery
at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileAsyncQueryCore
at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler+<>c__DisplayClass24_0`1.<CompileAsyncQuery>b__0
at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore
at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteAsync
at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.System.Collections.Generic.IAsyncEnumerable<TResult>.GetEnumerator
at System.Linq.AsyncEnumerable+<Aggregate_>d__6`3.MoveNext
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification
at BlayFap.Controllers.ServerController+<GetCachedApiCount>d__13.MoveNext (E:\Projects\BlayFap\BlayFap\Controllers\ServerController.cs:342)
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification
at BlayFap.Controllers.ServerController+<GetApiCount>d__14.MoveNext (E:\Projects\BlayFap\BlayFap\Controllers\ServerController.cs:378)
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification
at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker+<InvokeActionMethodAsync>d__12.MoveNext
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw
at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker+<InvokeNextActionFilterAsync>d__10.MoveNext
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw
at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow
at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next
at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker+<InvokeInnerFilterAsync>d__14.MoveNext
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw
at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker+<InvokeNextResourceFilter>d__22.MoveNext
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw
at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow
at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next
at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker+<InvokeFilterPipelineAsync>d__17.MoveNext
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification
at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker+<InvokeAsync>d__15.MoveNext
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw
所有其他表都可以正常访问，但是从这里开始尝试使用 ApiCounts 表会导致上述异常。我实际上必须重新启动受影响的服务器才能清除错误。看起来此异常与 Dictionary 上的并发编辑有关，并且 Dictionary 似乎在 linq 代码中。我猜服务器可能陷入这样一种情况，即 EF 在执行 linq 语句时同时更新和写入某种数据，然后让 Dictionary 陷入奇怪的状态，但我不知道如何防止这种情况以及真正的问题在哪里。这是 .NET 的错误，还是我自己的？
更多信息：我不会在此函数中修改 ApiCounts 的结果，也不会调用 SaveChanges。但是，与此异步运行的代码（在另一个 REST 查询中）可以更新 ApiCounts 并调用 SaveChanges。
【问题讨论】：
标签： c# entity-framework asp.net-core mysql-connector