Controlling Service Instances
A Windows Communication Foundation (WCF) service is an autonomous unit of execution with a published interface contract. Its functionality is exposed to the outside world through Windows Workflow Foundation (WF) endpoints. Instances of services are created when requests for its functionality are received by its endpoints when the services are hosted in the IIS/WAS environment. After instantiation, subsequent calls to invoke service operations, or to control the operation of the service, occur through the WF endpoints of a service. AppFabric transparently provides the capability to control persisted Workflow service instances through the use of an internal endpoint. This functionality is inherently provided by AppFabric for Workflow services that are configured to use its persistence features.
Within AppFabric, you can enumerate both persisted and tracked workflow service instances. However, you cannot execute any service control operations from with the AppFabric user interface on tracked workflow instances. Tracked workflow instances provide a historical record on a workflow instance (that may or may not be durable), and thus cannot be controlled. You can control only persisted workflow service instances from within AppFabric. You can run queries against the persisted (durable) workflow instance data to locate specific persisted instances. For example, you can filter on a specific workflow instance ID, creation time, completion time, last aborted time, status, machine name, or instance scope. You can also filter on the exception name, whether the instance is active, the time of the last persistence, the service ID, or the service name. You can filter the number of output rows to display based upon a maximum number of items (rows) you have chosen to return. For more information, refer to Persisted WF Instances Page, Windows Server AppFabric Dashboard Page, and Tracked WF Instances Page.
|Support for persisting and tracking of WCF service instances in AppFabric is not present in this release. The current release supports only persisting and tracking of workflow (WF) service instances. That is the reason why “View Persisted WF Instances” and “View Tracked WF Instances” options are available only on WF instances.|
The paradigm for service control command processing uses an asynchronous command queue. A user will be allowed to issue instance control commands from the Persisted WF Instances page only for those instances that do not already have pending commands in the queue. For more information, refer to Persisted WF Instances Page.
Users can also control persisted workflow service instances through Windows PowerShell cmdlets. This section describes how to control workflow service instances by using IIS Manager and AppFabric cmdlets.