.net 为Amazon Aurora的DNS数据设置TTL

我们正在使用Amazon Aurora（PostgreSQL），在尝试连接到数据库时会出现一些间歇性错误：

System.Net.Sockets.SocketException（0x80004005）：这通常是主机名解析过程中的临时错误，意味着本地服务器没有收到来自权威服务器的响应。

而且：

System.Exception:更新条目时出错。有关详细信息，请参见内部异常。-->System.Exception:检索InformationSchemaTable信息时出错。有关详细信息，请参见内部异常。-->System.Net.Sockets.SocketException：这通常是主机名解析期间出现的临时错误，意味着本地服务器没有收到来自权威服务器的响应

我们使用的是

npgsql3.2.5

。我们间歇性地从运行Windows server 2016的专用服务器和Azure应用程序服务上托管的代码接收此类错误。数百个连接成功，但有些（每小时几个）失败，并显示如下错误消息。发生连接时，数据库上没有明显的负载，连接数量也没有异常（远远超出限制）

我发现这一点：

如果客户端应用程序正在缓存数据库实例的域名服务（DNS）数据，请将生存时间（TTL）值设置为小于30秒。由于DB实例的基础IP地址在故障转移后可能会更改，因此如果应用程序尝试连接到不再使用的IP地址，则长时间缓存DNS数据可能会导致连接失败

所以我的问题是：如何知道我的客户端应用程序是否正在缓存DNS数据？有没有办法为Npgsql发出的请求设置TTL，或者必须在.NET或服务器上的某个常规位置设置TTL

编辑

所以在谢伊回答后，我又看了一眼。根据托管环境的不同，我们似乎会遇到两种不同类型的错误

托管在专用服务器上的代码会出现以下（DNS）错误：

System.Data.Entity.Core.ProviderIncompatibleException:从数据库获取提供程序信息时出错。这可能是由于实体框架使用了不正确的连接字符串造成的。有关详细信息，请检查内部异常，并确保连接字符串正确。-->System.Data.Entity.Core.ProviderIncompatibleException:提供程序未返回ProviderManifestToken字符串。-->System.Net.Sockets.SocketException：这通常是主机名解析期间出现的临时错误，意味着本地服务器没有收到来自权威服务器的响应
位于System.Net.Dns.GetAddrInfo（字符串名称）
位于System.Net.Dns.InternalGetHostByName（字符串主机名，布尔值includeIPv6）
位于System.Net.Dns.GetHostAddresses（字符串hostNameOrAddress）
在Npgsql.NpgsqlConnector.Connect上（NpgsqlTimeout超时）
在Npgsql.NpgsqlConnector.d__139.MoveNext（）中
---来自引发异常的上一个位置的堆栈结束跟踪---
在System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw（）中
在System.Runtime.CompilerServices.TaskWaiter.HandleNonSuccessAndDebuggerNotification（任务任务）中
在Npgsql.NpgsqlConnector.d__136.MoveNext（）中
---来自引发异常的上一个位置的堆栈结束跟踪---
在System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw（）中
在System.Runtime.CompilerServices.TaskWaiter.HandleNonSuccessAndDebuggerNotification（任务任务）中
在Npgsql.NpgsqlConnection.d_uu28.MoveNext（）中
---来自引发异常的上一个位置的堆栈结束跟踪---
在System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw（）中
在System.Runtime.CompilerServices.TaskWaiter.HandleNonSuccessAndDebuggerNotification（任务任务）中
在Npgsql.NpgsqlConnection.Open（）处
在Npgsql.NpgsqlServices.UsingPostgresDBConnection（NpgsqlConnection connection，Action`1 Action）
位于Npgsql.NpgsqlServices.GetDbProviderManifestToken（数据库连接）
位于System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken（DbConnection连接）
---内部异常堆栈跟踪的结束---
位于System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken（DbConnection连接）
位于System.Data.Entity.Utilities.DbProviderServicesExtensions.GetProviderManifestTokenChecked（DbProviderServices providerServices，DbConnection连接）
...

托管在Azure App Services中的同一代码出现以下（连接）错误：

System.InvalidOperationException:引发的异常可能是由于暂时性故障。-->Npgsql.NpgsqlException:从流读取时发生异常---->System.IO.IOException:无法从传输连接读取数据：连接尝试失败，因为连接方在一段时间后没有正确响应，或者由于连接主机未能响应而建立的连接失败。-->System.Net.Sockets.SocketException:连接尝试失败，因为连接方在一段时间后没有正确响应，或者建立的连接失败，因为连接的主机没有响应
位于System.Net.Sockets.Socket.EndReceive（IAsyncResult asyncResult）
位于System.Net.Sockets.NetworkStream.EndRead（IAsyncResult asyncResult）
---内部异常堆栈跟踪的结束---
位于System.Net.Sockets.NetworkStream.EndRead（IAsyncResult asyncResult）
在System.Threading.Tasks.TaskFactory`1.FromAsyncTrimPromission`1.Complete（t支持thisRef、Func`3 endMethod、IAsyncResult asyncResult、Boolean requiresSynchronization）
---来自引发异常的上一个位置的堆栈结束跟踪---
在System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw（）中
在Npgsql.ReadBuffer.d_u27.MoveNext（）中
---内部异常堆栈跟踪的结束---
在Npgsql.ReadBuffer.d_u27.MoveNext（）中
System.Data.Entity.Core.ProviderIncompatibleException: An error occurred while getting provider information from the database. This can be caused by Entity Framework using an incorrect connection string. Check the inner exceptions for details and ensure that the connection string is correct. ---> System.Data.Entity.Core.ProviderIncompatibleException: The provider did not return a ProviderManifestToken string. ---> System.Net.Sockets.SocketException: This is usually a temporary error during hostname resolution and means that the local server did not receive a response from an authoritative server
   at System.Net.Dns.GetAddrInfo(String name)
   at System.Net.Dns.InternalGetHostByName(String hostName, Boolean includeIPv6)
   at System.Net.Dns.GetHostAddresses(String hostNameOrAddress)
   at Npgsql.NpgsqlConnector.Connect(NpgsqlTimeout timeout)
   at Npgsql.NpgsqlConnector.<RawOpen>d__139.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlConnector.<Open>d__136.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlConnection.<Open>d__28.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlConnection.Open()
   at Npgsql.NpgsqlServices.UsingPostgresDBConnection(NpgsqlConnection connection, Action`1 action)
   at Npgsql.NpgsqlServices.GetDbProviderManifestToken(DbConnection connection)
   at System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken(DbConnection connection)
   --- End of inner exception stack trace ---
   at System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken(DbConnection connection)
   at System.Data.Entity.Utilities.DbProviderServicesExtensions.GetProviderManifestTokenChecked(DbProviderServices providerServices, DbConnection connection)
...

System.InvalidOperationException: An exception has been raised that is likely due to a transient failure. ---> Npgsql.NpgsqlException: Exception while reading from stream ---> System.IO.IOException: Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. ---> System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond
   at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)
   at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)
   --- End of inner exception stack trace ---
   at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)
   at System.Threading.Tasks.TaskFactory`1.FromAsyncTrimPromise`1.Complete(TInstance thisRef, Func`3 endMethod, IAsyncResult asyncResult, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Npgsql.ReadBuffer.<Ensure>d__27.MoveNext()
   --- End of inner exception stack trace ---
   at Npgsql.ReadBuffer.<Ensure>d__27.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Npgsql.NpgsqlConnector.<DoReadMessage>d__148.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Npgsql.NpgsqlConnector.<ReadPrependedMessages>d__150.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlConnector.<ReadMessage>d__147.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlConnector.<ReadExpecting>d__154`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Npgsql.NpgsqlDataReader.<NextResult>d__32.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlDataReader.<<NextResultAsync>b__31_0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlCommand.<Execute>d__71.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlCommand.<ExecuteDbDataReader>d__92.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlCommand.<>c__DisplayClass90_0.<<ExecuteDbDataReaderAsync>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.<ExecuteAsync>d__17.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncQueryingEnumerable`1.AsyncEnumerator.<BufferlessMoveNext>d__12.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Storage.Internal.NpgsqlExecutionStrategy.<ExecuteAsync>d__7`2.MoveNext()
   --- End of inner exception stack trace ---
   at Microsoft.EntityFrameworkCore.Storage.Internal.NpgsqlExecutionStrategy.<ExecuteAsync>d__7`2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncQueryingEnumerable`1.AsyncEnumerator.<MoveNext>d__11.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Linq.AsyncEnumerable.<FirstOrDefault_>d__165`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.TaskResultAsyncEnumerable`1.Enumerator.<MoveNext>d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Linq.AsyncEnumerable.SelectEnumerableAsyncIterator`2.<MoveNextCore>d__7.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Linq.AsyncEnumerable.AsyncIterator`1.<MoveNext>d__10.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.<MoveNext>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<ExecuteSingletonAsyncQuery>d__21`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at OpenIddict.OpenIddictProvider`4.<HandleTokenRequest>d__25.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at AspNet.Security.OpenIdConnect.Server.OpenIdConnectServerHandler.<InvokeTokenEndpointAsync>d__20.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at AspNet.Security.OpenIdConnect.Server.OpenIdConnectServerHandler.<HandleRequestAsync>d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.<Invoke>d__6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Cors.Infrastructure.CorsMiddleware.<Invoke>d__8.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Localization.RequestLocalizationMiddleware.<Invoke>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Server.IISIntegration.IISMiddleware.<Invoke>d__13.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.<ProcessRequests>d__188`1.MoveNext()