.Net Core Oracle Connection time out

Question

we have application .net core with oracle database published since 8 months unexpectedly returned request connection time and we didn't make any deployment and we didn't use it much time because we are waiting for phase 2

.Net Core 5 Packages version

1. Microsoft.EntityFrameworkCore >> 5.0.17
2. Oracle.ManagedDataAccess.Client >> 3.21.61
3. Oracle.EntityFrameworkCore >> 5.21.61

we tried the following:

• Restart IIS

• restart the app server

• restart the database server

• increase the time out in the connection string

• increase min & max pool size

• I tried Dapper and gave the same error

• I created the small app with one DB set (table) and deployed on
  the server it is worked successfully on the same database and same server

• telnet on the database server from server and worked

Some Notes:

• the application always now gave request connection time on the production server.
• the application works with the same database on the visual studio on my machine.
• and also I deployed the app on my machine and worked
• the Issue is only on production servers
• we access the database from local machine using VPN

the log below:

{ "time": "2022-05-13 00:28:40.8846", "level": "ERROR(Microsoft.EntityFrameworkCore.Database.Connection)", "url": "http:\/\/dedportal.uaqgov.ae\/api\/Activity\/ActivityListAll", "actionName": "ActivityListAll", "Message": "An error occurred using the connection to database '' on server host\/service name'." },


{ "time": "2022-05-13 00:28:40.9270", "level": "ERROR(Microsoft.EntityFrameworkCore.Infrastructure)", "url": "http:\/\/dedportal.uaqgov.ae\/api\/Activity\/ActivityListAll", "actionName": "ActivityListAll", "Message": "1443-10-12 00:28:40.923393 ThreadID:4   (ERROR)   OracleExecutionStrategy.ExecuteAsync() :  Oracle.ManagedDataAccess.Client.OracleException (0x80004005): Connection request timed out
  at OracleInternal.ConnectionPool.PoolManager`3.Get(ConnectionString csWithDiffOrNewPwd, Boolean bGetForApp, OracleConnection connRefForCriteria, String affinityInstanceName, Boolean bForceMatch)
  at OracleInternal.ConnectionPool.OraclePoolManager.Get(ConnectionString csWithNewPassword, Boolean bGetForApp, OracleConnection connRefForCriteria, String affinityInstanceName, Boolean bForceMatch)
  at OracleInternal.ConnectionPool.OracleConnectionDispenser`3.Get(ConnectionString cs, PM conPM, ConnectionString pmCS, SecureString securedPassword, SecureString securedProxyPassword, OracleConnection connRefForCriteria)
  at Oracle.ManagedDataAccess.Client.OracleConnection.Open()
  at System.Data.Common.DbConnection.OpenAsync(CancellationToken cancellationToken)\r\n--- End of stack trace from previous location ---
  at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenInternalAsync(Boolean errorsExpected, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenInternalAsync(Boolean errorsExpected, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenAsync(CancellationToken cancellationToken, Boolean errorsExpected)
  at Oracle.EntityFrameworkCore.Storage.Internal.OracleRelationalCommandBuilderFactory.OracleRelationalCommandBuilder.OracleRelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.AsyncEnumerator.InitializeReaderAsync(DbContext _, Boolean result, CancellationToken cancellationToken)
  at Oracle.EntityFrameworkCore.Storage.Internal.OracleExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellationToken)" },



{ "time": "2022-05-13 00:28:40.9660", "level": "ERROR(Microsoft.EntityFrameworkCore.Query)", "url": "http:\/\/dedportal.uaqgov.ae\/api\/Activity\/ActivityListAll", "actionName": "ActivityListAll", "ExceptionType": "Oracle.ManagedDataAccess.Client.OracleException", "ExceptionMessage": "Connection request timed out", "StackTrace": "   at OracleInternal.ConnectionPool.PoolManager`3.Get(ConnectionString csWithDiffOrNewPwd, Boolean bGetForApp, OracleConnection connRefForCriteria, String affinityInstanceName, Boolean bForceMatch)
  at OracleInternal.ConnectionPool.OraclePoolManager.Get(ConnectionString csWithNewPassword, Boolean bGetForApp, OracleConnection connRefForCriteria, String affinityInstanceName, Boolean bForceMatch)
  at OracleInternal.ConnectionPool.OracleConnectionDispenser`3.Get(ConnectionString cs, PM conPM, ConnectionString pmCS, SecureString securedPassword, SecureString securedProxyPassword, OracleConnection connRefForCriteria)
  at Oracle.ManagedDataAccess.Client.OracleConnection.Open()
  at System.Data.Common.DbConnection.OpenAsync(CancellationToken cancellationToken)\r\n--- End of stack trace from previous location ---
  at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenInternalAsync(Boolean errorsExpected, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenInternalAsync(Boolean errorsExpected, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenAsync(CancellationToken cancellationToken, Boolean errorsExpected)
  at Oracle.EntityFrameworkCore.Storage.Internal.OracleRelationalCommandBuilderFactory.OracleRelationalCommandBuilder.OracleRelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.AsyncEnumerator.InitializeReaderAsync(DbContext _, Boolean result, CancellationToken cancellationToken)
  at Oracle.EntityFrameworkCore.Storage.Internal.OracleExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.AsyncEnumerator.MoveNextAsync()", "Message": "An exception occurred while iterating over the results of a query for context type 'UAQDED.Infrastructure.DB.DBContext.ModelContext'.\r\nOracle.ManagedDataAccess.Client.OracleException (0x80004005): Connection request timed out
  at OracleInternal.ConnectionPool.PoolManager`3.Get(ConnectionString csWithDiffOrNewPwd, Boolean bGetForApp, OracleConnection connRefForCriteria, String affinityInstanceName, Boolean bForceMatch)
  at OracleInternal.ConnectionPool.OraclePoolManager.Get(ConnectionString csWithNewPassword, Boolean bGetForApp, OracleConnection connRefForCriteria, String affinityInstanceName, Boolean bForceMatch)
  at OracleInternal.ConnectionPool.OracleConnectionDispenser`3.Get(ConnectionString cs, PM conPM, ConnectionString pmCS, SecureString securedPassword, SecureString securedProxyPassword, OracleConnection connRefForCriteria)
  at Oracle.ManagedDataAccess.Client.OracleConnection.Open()
  at System.Data.Common.DbConnection.OpenAsync(CancellationToken cancellationToken)\r\n--- End of stack trace from previous location ---
  at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenInternalAsync(Boolean errorsExpected, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenInternalAsync(Boolean errorsExpected, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenAsync(CancellationToken cancellationToken, Boolean errorsExpected)
  at Oracle.EntityFrameworkCore.Storage.Internal.OracleRelationalCommandBuilderFactory.OracleRelationalCommandBuilder.OracleRelationalCommand.ExecuteReaderAsync(RelationalCommandParameterObject parameterObject, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.AsyncEnumerator.InitializeReaderAsync(DbContext _, Boolean result, CancellationToken cancellationToken)
  at Oracle.EntityFrameworkCore.Storage.Internal.OracleExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellationToken)
  at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.AsyncEnumerator.MoveNextAsync()" },

Answer 1

We solved this it seems that our scan listeners have an issue I used the IP of the database nodes and it is working.