Up Client tier

Configure auto retry

Last modified on August 05, 2014 12:19

An n-tier DevForce client application may experience sometimes transient communication-related failures.  For some of these failures DevForce will automatically retry based on default settings, but you can also configure auto retry options.


Default behavior

For EntityManager actions other than SaveChanges, such as Connect and query, and for Authenticator.Login, the CommunicationSettings.Default.DefaultRetryPolicy is used.  This in turn defaults to a FixedRetry policy which will attempt 3 retries with a half-second delay between each attempt.

For EntityManager save operations, including ForceIdFixup, the CommunicationSettings.Default.DefaultRetryPolicyForSave is used, which defaults to a NoRetry policy.  

To set your own application-wide defaults you can change either the DefaultRetryPolicy or DefaultRetryPolicyForSave as needed.

For example, to set the DefaultRetryPolicy to perform 2 retries with a 1 second delay between tries:

C#
using IdeaBlade.Core;
using IdeaBlade.Core.Wcf.Extensions;

CommunicationSettings.Default.DefaultRetryPolicy = new FixedRetry { MaxTries = 2, Delay = TimeSpan.FromSeconds(1) };

A retry for a save operation is not advised, unless you can inspect the exception to ensure that the request never reached the server.  You can implement a custom IRetryPolicy to inspect the exception to determine if a retry can be done.

For example:

C#
using IdeaBlade.Core;

public class MyRetryPolicy : IRetryPolicy  {

 // Allow 2 retries for EndpointNotFound errors.
 public bool ShouldRetry(int currentRetryCount, Exception exception, out TimeSpan delay) {
    delay = TimeSpan.FromSeconds(1);
   if (exception is System.ServiceModel.EndpointNotFoundException) {
     return currentRetryCount < 2;
    } else {
     return false;
    }
  }
}

Per request overrides

Several EntityManager actions can also use a custom retry policy for the request.

For queries, the QueryStrategy.CommunicationRetryPolicy can be set.

For example:

C#
var qs = QueryStrategy.Normal.With(new FixedRetry { MaxTries = 5, Delay = TimeSpan.FromMilliseconds(100) });
var customers = await entityManager.Customers.With(qs).ExecuteAsync();

Individual save operations can also use a custom policy, using SaveOptions.CommunicationRetryPolicy.  As noted above, use caution if you implement a retry for save operations.

Calls to remote server methods may use a custom retry policy when using the InvokeServerMethod (or InvokeServerMethodAsync) override which accepts an InvokeServerMethodArgs parameter.

For example:

C#
// Call an RPC method with NoRetry
var args = new InvokeServerMethodArgs {
  FullTypeName = "DomainModel.ServerMethods, DomainModel",
  MethodName = "GetNumberOfOrders",
  ClientArgs = new object[] { 10, new DateTime(1995, 1,1), new DateTime(1999, 1,
  CommunicationRetryPolicy = new NoRetry()
};

var num = (int)entityManager.InvokeServerMethod(args);
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Created by DevForce on August 05, 2014 11:07

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