I have a web service method I am calling which is 3rd party and outside of my domain. For some reason every now and again the web service fails with a gateway timeout. Its i
You can do it in a loop.
Exception firstEx = null;
for(int i=0; i<5; i++)
{
try
{
MDO = OperationsWebService.MessageDownload(MI);
firstEx = null;
break;
}
catch(Exception ex)
{
if (firstEx == null)
{
firstEx = ex;
}
Thread.Sleep(100 * (i + 1));
}
}
if (firstEx != null)
{
throw new Exception("WebService call failed after 5 retries.", firstEx);
}
I'm using the following generic method for a retry scenario. I especially want to draw attention to the PreserveStackTrace method which helps to preserve the full call stack trace, because (as I learned the hard way) neither throw
or throw ex
yields the complete call stack trace information.
public static void RetryBeforeThrow<T>(Action action, int retries, int timeout) where T : Exception
{
int tries = 1;
do
{
try
{
action();
return;
}
catch (T ex)
{
if (retries <= 0)
{
PreserveStackTrace(ex);
throw;
}
Thread.Sleep(timeout);
}
}
while (tries++ < retries);
}
/// <summary>
/// Sets a flag on an <see cref="T:System.Exception"/> so that all the stack trace information is preserved
/// when the exception is re-thrown.
/// </summary>
/// <remarks>This is useful because "throw" removes information, such as the original stack frame.</remarks>
/// <see href="http://weblogs.asp.net/fmarguerie/archive/2008/01/02/rethrowing-exceptions-and-preserving-the-full-call-stack-trace.aspx"/>
public static void PreserveStackTrace(Exception ex)
{
MethodInfo preserveStackTrace = typeof(Exception).GetMethod("InternalPreserveStackTrace", BindingFlags.Instance | BindingFlags.NonPublic);
preserveStackTrace.Invoke(ex, null);
}
It seems you have the answers you need, but I thought I'd post this link, What is an Action Policy?, that I found to provide a much more elegant solution. Lokad has some rather labyrinthine implementations, but the guy's logic is pretty solid, and the end code you'd end up writing is pretty and simple.
As everyone else has pointed out the correct approach is to wrap your try/catch inside some loop with a MAX_RETRY of some sort.
You might also consider adding a timeout between each loop iteration. Otherwise you're likely to burn through your retry counter before the transient issue has had a chance to resolve itself.