Executing work from a "VeroServe Workflow"

While the interaction of an enterprise user application with its back-end services is orchestrated in a “VeroServe Workflow”, execution of intensive or performance sensitive “VeroServe Workflow” work can in turn be delegated to one or more instances of ExecuteServe for load balancing across servers. “VeroServe Workflow” hides the details of delegating work to ExecuteServe through its ExecuteActivity.

To use ExecuteActivity, first add it to VS by hovering over the toolbar when displaying a work flow, right clicking, selecting the “System.Activities.Components” tab, then browsing for ExecutionActivity.dll (built from svn://[repositoryAddress]/[company]/WorkflowServices/WorkflowServices.sln). Then, drag it to the appropriate location in your work flow. 

ExecuteActivity requires configuration of the following in and out parameters:

ExecuteActivity.DLL Activity Control:

In Parameters:
   callbackAddress          String
   workflowInstanceId       String
   executeActivityNumber    String
   worker                   Worker
   executionServiceAddress  String


Out Parameters:
   executeReturnParameter   ExecuteReturnParameter


    public class ExecuteReturnParameter
    {
        public string Status { ... }
        public string Message { ... }
        public string AssemblyName { ... }
        public string ClassName { get; set; }
        public string SerializedWorker { ... }
        public ExecuteParameter ExecutionParameter { ... }
    }

Work flows containing the ExecuteActivity must also have a client endpoint element in its web.config named "IExecutionServiceEndpointConfigurationName". The following web.config entry can be directly cut/pasted into a "VeroServe Workflow" web.config without any modification to satisfy this requirement:

Web.config Settings:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.serviceModel>
    <bindings>
      <basicHttpBinding>
        <binding name="BasicHttpBinding_IExecutionService" .... >
        </binding>
      </basicHttpBinding>
    </bindings>
    <client>
      <endpoint binding="basicHttpBinding" 
        bindingConfiguration="BasicHttpBinding_IExecutionService" contract="IExecutionService" address="http://localhost/ExecutionService.svc"
        name="IExecutionServiceEndpointConfigurationName" />
    </client>
  </system.serviceModel>
</configuration>

The following figure is an example of settings for ExecuteActivity parameters:

ExecuteActivity's in parameters include:

• callbackAddress, the execution URL of the “VeroServe Workflow” containing the ExecuteActivity. In this figure, this "VeroServe Workflow" is configured to execute at "http://localhost:1392/PayoutWorkflowService.xamlx".
• workflowInstanceId, a unique number that identifies the instance of the "VeroServe Workflow" executing. In this example, the variable workflowId was set in "VeroServe Workflow" prior to this ExecuteActivity with a unique Guid generated for the executing instance.
• executeActivityNumber, a unique constant that identifies the ExecuteActivity within the "VeroServe Workflow". In this example, the variable invocationNumber was set to a constant that uniquely identifies this ExecuteActivity within the "VeroServe Workflow".
• worker, an instance of a derivative of Worker, with its DataMember-decorated properties set to their values in preparation for execution within ExecutionServe.
• executionServiceAddress, the URL of an ExecutionServe service.

ExecuteActivity also requres an ExecuteReturnParameter out parameter defined in Entities.dll (built from svn://[repositoryAddress]/[company]/WorkflowServices/WorkflowServices.sln), which will include a Worker-defined status and an ExecutionParameter that can be used by Worker's desearalize() static method to re-instantiate the Worker within the work flow after ExecuteActivity completes. Modifications made to any Worker property decorated with the [DataMember] attribute during execution directed by ExecuteActivity will be subsequently reflected in these deserialized values.

    public abstract class Worker
    {
        public static Worker deserialize(ExecuteParameter executeParameter)
        { ... }
        }

        public ExecuteParameter serialize()
        { ... }

    }