查询在 Azure 上超时，但不是来自同一数据库上的本地主机

Question

我有一个从 Azure 应用服务运行时超时的查询（命令超时设置为 600 秒以进行测试）。当我从 Visual Studio 在本地运行网站并连接到与应用服务完全相同的数据库时，相同的查询需要 9-11 秒才能运行。

Azure 应用服务计划 - P2V2 Azure SQL Server 计划 - S4

网站是 ASP Core 3.1 使用 EF Core 3.1

我进行了一些研究，发现来自不同环境的不同查询行为的可能原因可能是由于参数嗅探。不幸的是，我不知道我能做些什么来解决这个问题。

为了提供更多上下文，我今天在尝试查询之前尝试重新计算数据库索引，并且我还运行了DBCC FREEPROCCACHE。

具有相同参数的相关查询的日志显示：

Azure 应用服务：

[41m[30mfail[39m[22m[49m: Microsoft.EntityFrameworkCore.Database.Command[20102]
Failed executing DbCommand (600,117ms) 
[Parameters=
[@__impersonateId_0='76889' (Nullable = true), 
@__impersonateId_1='76889' (Nullable = true), 
@__reportFilter_From_2='2019-01-01T00:00:00' (Nullable = true), 
@__reportFilter_To_3='2019-12-31T00:00:00' (Nullable = true), 
@__key_TransportationType_4='Rail' (Size = 450), 
@__key_CostCenter_5='' (Size = 4000)], 
CommandType='Text', CommandTimeout='600']

本地主机：

info: Microsoft.EntityFrameworkCore.Database.Command[20101]
Executed DbCommand (11,534ms) 
[Parameters=
[@__impersonateId_0='76889' (Nullable = true), 
@__impersonateId_1='76889' (Nullable = true), 
@__reportFilter_From_2='2019-01-01T00:00:00' (Nullable = true), 
@__reportFilter_To_3='2019-12-31T00:00:00' (Nullable = true), 
@__key_TransportationType_4='Rail' (Size = 450), 
@__key_CostCenter_5='' (Size = 4000)], 
CommandType='Text', CommandTimeout='600']

堆栈跟踪如下：

[41m[30mfail[39m[22m[49m: Microsoft.EntityFrameworkCore.Query[10100]
An exception occurred while iterating over the results of a query for context type '...'.
Microsoft.Data.SqlClient.SqlException (0x80131904): Execution Timeout Expired.  The timeout period elapsed prior to completion of the operation or the server is not responding.
 ---> System.ComponentModel.Win32Exception (258): Unknown error 258
   at Microsoft.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at Microsoft.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at Microsoft.Data.SqlClient.SqlDataReader.TryConsumeMetaData()
   at Microsoft.Data.SqlClient.SqlDataReader.get_MetaData()
   at Microsoft.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString, Boolean isInternal, Boolean forDescribeParameterEncryption, Boolean shouldCacheForAlwaysEncrypted)
   at Microsoft.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean isAsync, Int32 timeout, Task& task, Boolean asyncWrite, Boolean inRetry, SqlDataReader ds, Boolean describeParameterEncryptionRequest)
   at Microsoft.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry, String method)
   at Microsoft.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior)
   at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReader(RelationalCommandParameterObject parameterObject)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable`1.Enumerator.InitializeReader(DbContext _, Boolean result)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.Execute[TState,TResult](TState state, Func`3 operation, Func`3 verifySucceeded)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable`1.Enumerator.MoveNext()
ClientConnectionId:...
Error Number:-2,State:0,Class:11
ClientConnectionId before routing:...
Routing Destination:...-a.worker.database.windows.net,11016

我可以做些什么来进一步研究从 Azure 应用服务中运行查询超时的原因？

Answer 1

由于您提到并且从跟踪中可以看出，相同的操作在 localhost 上完美运行，但限制了 App 服务，可能应该升级当前的应用程序服务计划。

如果您使用基于消费的计划，则超时值可以是 10 分钟，或者如果您使用高级版，则超时值是无限制的。如果触发器是 HTTP，那么无论如何超时都是 230 秒，这是由于 Azure 负载均衡器的默认空闲 timeout。

您可以尝试使用article 进行故障排除或参考：here 类似问题。

缓解这种情况的一些常用方法：

1. Scale the web app
2. Use AutoHeal
3. Restart the web app