user1638662 user1638662 - 3 months ago 44
C# Question

Implementing retry logic for deadlock exceptions

I've implemented a generic repository and was wondering if there is a smart way to implement a retry logic in case of a deadlock exception?

The approach should be the same for all repository methods. So is there anyway I can avoid writing 'try/catch - call method again with retry-count', in every single method?

Any suggetsion are welcome.

A bit of my Repository code:

public class GenericRepository : IRepository
{
private ObjectContext _context;

public List<TEntity> ExecuteStoreQuery<TEntity>(string commandText, params object[] parameters) where TEntity : class
{
List<TEntity> myList = new List<TEntity>();

var groupData = _context.ExecuteStoreQuery<TEntity>(commandText, parameters);

return myList;
}


public IQueryable<TEntity> GetQuery<TEntity>() where TEntity : class
{
var entityName = GetEntityName<TEntity>();
return _context.CreateQuery<TEntity>(entityName);
}

public IEnumerable<TEntity> GetAll<TEntity>() where TEntity : class
{
return GetQuery<TEntity>().AsEnumerable();
}


EDIT:

1.Solution:

Modified slightly from chris.house.00's solution

public static T DeadlockRetryHelper<T>(Func<T> repositoryMethod, int maxRetries)
{
var retryCount = 0;

while (retryCount < maxRetries)
{
try
{
return repositoryMethod();
}
catch (System.Data.SqlClient.SqlException ex)
{
if (ex.Number == 1205)// Deadlock
retryCount++;
else
throw;
}
}
return default(T);
}


And you call it like this:

public TEntity FirstOrDefault<TEntity>(Expression<Func<TEntity, bool>> predicate) where TEntity : class
{
return RetryUtility.DeadlockRetryHelper<TEntity>( () =>p_FirstOrDefault<TEntity>(predicate), 3);
}

protected TEntity p_FirstOrDefault<TEntity>(Expression<Func<TEntity, bool>> predicate) where TEntity : class
{
return GetQuery<TEntity>().FirstOrDefault<TEntity>(predicate);
}

Answer

How about something like this:

public T DeadlockRetryHelper<T>(Func<T> repositoryMethod, int maxRetries)
{
  int retryCount = 0;

  while (retryCount < maxRetries)
  {
    try
    {
      return repositoryMethod();
    }
    catch (SqlException e) // This example is for SQL Server, change the exception type/logic if you're using another DBMS
    {
      if (e.Number == 1205)  // SQL Server error code for deadlock
      {
        retryCount++;
      }
      else
      {
        throw;  // Not a deadlock so throw the exception
      }
      // Add some code to do whatever you want with the exception once you've exceeded the max. retries
    }
  }
}

With the above code, your retry logic is all in this method and you can just pass your repository method in as a delegate.