Throw a specific exception for deadlocks #11

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1. madelson commented on Nov 15, 2017

   

   madelson

   on Nov 15, 2017

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   Hi @oliverhanappi thank you for your interest in the library.

   I'm curious whether you've ever seen the deadlock exit code returned. I remember trying to force this a while back and not seeing it.

   Provided we can create a test case where this is actually returned, this suggestion makes sense and would be an easy enhancement. For backwards compat, the new exception should extend InvalidOperationException.
2. oliverhanappi commented on Nov 15, 2017

   

   oliverhanappi

   on Nov 15, 2017

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   It is actually pretty easy. You just need to acquire multiple locks within the same connection or transaction such that two connections/transactions are waiting on each other. Here is a simple repro:

   using System;
   using System.Data.SqlClient;
   using System.Threading;
   using System.Threading.Tasks;
   using Medallion.Threading.Sql;
   
   namespace SqlDistributedLockDeadlock
   {
     public static class Program
     {
       public static void Main ()
       {
         using (var barrier = new Barrier (2))
         {
           var task1 = Task.Run (() => WithTransaction((connection, transaction) =>
           {
             new SqlDistributedLock ("test1", transaction).Acquire();
             barrier.SignalAndWait();
             new SqlDistributedLock ("test2", transaction).Acquire();
           }));
           
           var task2 = Task.Run (() => WithTransaction((connection, transaction) =>
           {
             new SqlDistributedLock ("test2", transaction).Acquire();
             barrier.SignalAndWait();
             new SqlDistributedLock ("test1", transaction).Acquire();
           }));
   
           Task.WaitAll (task1, task2);
         }
       }
   
       private static void WithTransaction (Action<SqlConnection, SqlTransaction> action)
       {
         const string connectionString = "Server=localhost;Database=Playground;Integrated Security=True";
   
         using (var connection = new SqlConnection (connectionString))
         {
           connection.Open();
   
           using (var transaction = connection.BeginTransaction())
             action.Invoke (connection, transaction);
   
           connection.Close();
         }
       }
     }
   }
   
3. madelson

   added

   enhancement

   on Jan 12, 2018
4. madelson

   added 2 commits that reference this issue on Feb 7, 2018

   Address #11 by throwing a specific exception type (DeadlockException)…

   ...

   da6fe80

   Merge pull request #17 from madelson/deadlock-exception

   ...

   ea0a900
5. madelson commented on Feb 8, 2018

   

   madelson

   on Feb 8, 2018

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   This is addressed as of version 1.4

   👍React with 👍1Reacted by Peter Morris
6. madelson

   closed this as completedon Feb 8, 2018