A client of ours is experiencing some instability on one of their Umbraco sites. It's running 7.4.3, with Simple 301 redirect module.

There is an error that occurs quite regularly (logged in Umbraco log), in which it appears the Simple301 module is calling Umbraco.Core.Persistence.Migrations.MigrationRunner.Execute(), and throwing the following exception:

2016-10-13 11:17:43,121 [P17024/D3/T90] ERROR Umbraco.Core.Persistence.Migrations.MigrationRunner - Error running Redirects migration
System.Data.SqlClient.SqlException (0x80131904): Column names in each table must be unique. Column name 'IsRegex' in table 'Redirects' is specified more than once.
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at Umbraco.Core.Persistence.PetaPocoCommandExtensions.<>c__DisplayClass1.<ExecuteNonQueryWithRetry>b__0()
   at Umbraco.Core.Persistence.FaultHandling.RetryPolicy.ExecuteAction[TResult](Func`1 func)
   at Umbraco.Core.Persistence.Database.Execute(String sql, Object[] args)
   at Umbraco.Core.Persistence.Migrations.MigrationRunner.ExecuteMigrations(IMigrationContext context, Database database)
   at Umbraco.Core.Persistence.Migrations.MigrationRunner.Execute(Database database, DatabaseProviders databaseProvider, Boolean isUpgrade)
   at Simple301.Core.MyApplication.HandleMigrations()
ClientConnectionId:6164411c-be82-49b8-9caa-cd55bfdd9afb
Error Number:2705,State:4,Class:16

and...

2016-10-13 11:17:43,121 [P17024/D3/T90] ERROR Umbraco.Core.Persistence.UmbracoDatabase - Database exception occurred
System.Data.SqlClient.SqlException (0x80131904): Column names in each table must be unique. Column name 'IsRegex' in table 'Redirects' is specified more than once.
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at Umbraco.Core.Persistence.PetaPocoCommandExtensions.<>c__DisplayClass1.<ExecuteNonQueryWithRetry>b__0()
   at Umbraco.Core.Persistence.FaultHandling.RetryPolicy.ExecuteAction[TResult](Func`1 func)
   at Umbraco.Core.Persistence.Database.Execute(String sql, Object[] args)
ClientConnectionId:6164411c-be82-49b8-9caa-cd55bfdd9afb Error Number:2705,State:4,Class:16

After this happens a few times, the app pool crashes and recycles. I'm not sure if this is a cause of the instability, but it definitely shouldn't be happening. I haven't dug into the code yet to figure out why this is happening, and will do that if I get more time to work on this, but thought maybe somebody out there has seen this before and can advise?

Cheers Greg