查询的时候每隔一次出现Unknown command错误

[Codespilot]

环境：
EntityFramework Core 3.1 + Pomelo.EntityFrameworkCore.MySql

问题描述：
使用MyCat查询的时候出现Unknown command异常，跨库或者单库都会。并且是一次正常一次出错交替出现的。
PS：之前使用ShardingSphere也有相同的情况，错误信息是：Unsupported command: COM_RESET_CONNECTION。

错误详细：

[ERR] Unknown command
MySql.Data.MySqlClient.MySqlException (0x80004005): Unknown command
   at MySqlConnector.Core.ServerSession.ReceiveReplyAsyncAwaited(ValueTask`1 task) in C:\projects\mysqlconnector\src\MySqlConnector\Core\ServerSession.cs:line 775
   at MySqlConnector.Core.ServerSession.TryResetConnectionAsync(ConnectionSettings cs, IOBehavior ioBehavior, CancellationToken cancellationToken) in C:\projects\mysqlconnector\src\MySqlConnector\Core\ServerSession.cs:line 520
   at MySqlConnector.Core.ConnectionPool.GetSessionAsync(MySqlConnection connection, IOBehavior ioBehavior, CancellationToken cancellationToken) in C:\projects\mysqlconnector\src\MySqlConnector\Core\ConnectionPool.cs:line 143
   at MySqlConnector.Core.ConnectionPool.GetSessionAsync(MySqlConnection connection, IOBehavior ioBehavior, CancellationToken cancellationToken) in C:\projects\mysqlconnector\src\MySqlConnector\Core\ConnectionPool.cs:line 143
   at MySql.Data.MySqlClient.MySqlConnection.CreateSessionAsync(ConnectionPool pool, Nullable`1 ioBehavior, CancellationToken cancellationToken) in C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlConnection.cs:line 670
   at MySql.Data.MySqlClient.MySqlConnection.OpenAsync(Nullable`1 ioBehavior, CancellationToken cancellationToken) in C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlConnection.cs:line 332
   at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenDbConnectionAsync(Boolean errorsExpected, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenDbConnectionAsync(Boolean errorsExpected, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenAsync(CancellationToken cancellationToken, Boolean errorsExpected)
   at Pomelo.EntityFrameworkCore.MySql.Storage.Internal.MySqlRelationalConnection.OpenAsync(CancellationToken cancellationToken, Boolean errorsExpected)
   at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable`1.AsyncEnumerator.InitializeReaderAsync(DbContext _, Boolean result, CancellationToken cancellationToken)
   at Pomelo.EntityFrameworkCore.MySql.Storage.Internal.MySqlExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable`1.AsyncEnumerator.MoveNextAsync()
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToListAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToListAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
   at KdsA1.System.Domain.Lovs.LovTypes.EfCore.LovTypeRepository.GetPageListAsync(LovTypeQueryDto condition) in /home/kdsa1-user/azure-devops-agent/_work/3/s/src/services/SystemService/KdsA1.System.Domain/Lovs/LovTypes/EfCore/LovTypeRepository.cs:line 52
   at KdsA1.System.Application.Services.Lovs.LovTypeAppService.GetPageListAsync(LovTypeQueryDto input) in /home/kdsa1-user/azure-devops-agent/_work/3/s/src/services/SystemService/KdsA1.System.Application/Services/Lovs/LovTypeAppService.cs:line 52
   at Castle.DynamicProxy.AsyncInterceptorBase.ProceedAsynchronous[TResult](IInvocation invocation, IInvocationProceedInfo proceedInfo)
   at Volo.Abp.Castle.DynamicProxy.CastleAbpMethodInvocationAdapterWithReturnValue`1.ProceedAsync()
   at Volo.Abp.Validation.ValidationInterceptor.InterceptAsync(IAbpMethodInvocation invocation)
   at Volo.Abp.Castle.DynamicProxy.CastleAsyncAbpInterceptorAdapter`1.InterceptAsync[TResult](IInvocation invocation, IInvocationProceedInfo proceedInfo, Func`3 proceed)
   at Castle.DynamicProxy.AsyncInterceptorBase.ProceedAsynchronous[TResult](IInvocation invocation, IInvocationProceedInfo proceedInfo)
   at Volo.Abp.Castle.DynamicProxy.CastleAbpMethodInvocationAdapterWithReturnValue`1.ProceedAsync()
   at Volo.Abp.Auditing.AuditingInterceptor.InterceptAsync(IAbpMethodInvocation invocation)
   at Volo.Abp.Castle.DynamicProxy.CastleAsyncAbpInterceptorAdapter`1.InterceptAsync[TResult](IInvocation invocation, IInvocationProceedInfo proceedInfo, Func`3 proceed)
   at Castle.DynamicProxy.AsyncInterceptorBase.ProceedAsynchronous[TResult](IInvocation invocation, IInvocationProceedInfo proceedInfo)
   at Volo.Abp.Castle.DynamicProxy.CastleAbpMethodInvocationAdapterWithReturnValue`1.ProceedAsync()
   at Volo.Abp.Uow.UnitOfWorkInterceptor.InterceptAsync(IAbpMethodInvocation invocation)
   at Volo.Abp.Castle.DynamicProxy.CastleAsyncAbpInterceptorAdapter`1.InterceptAsync[TResult](IInvocation invocation, IInvocationProceedInfo proceedInfo, Func`3 proceed)

[junwen12221]

最新的mycat版本设置ignoreUnknownCommand属性

[funnyAnt]

参考 https://dev.mysql.com/doc/dev/mysql-server/8.0.11/page_protocol_com_reset_connection.html
https://dev.mysql.com/doc/refman/5.7/en/mysql-reset-connection.html， 已经提交PR.

几点说明：

• 和原始mysql差异地方：

  • mysql协议是自动commit掉未提交的事务，但是mycat如果自动commit，会多一个回包给客户端。 为了简单处理，统一关闭后端连接。

• 调试过程中，发现Mycat的潜在bug， session.closeAndClearResources（）函数，会触发一次connectionClosed()函数回调，多一个回包给客户端，没有另外提单，顺手优化。