Built-in Configuration

  • Article

This topic applies to Windows Workflow Foundation 4 (WF4).

This sample demonstrates the use and configuration of the SQL workflow instance store. The SQL workflow instance store is a SQL-based implementation of an instance store. It allows an instance to save and load its state to and from a SQL Server or SQL Server Express database.

Ee622978.Important(en-us,VS.100).gif Note:
The samples may already be installed on your computer. Check for the following (default) directory before continuing.

<InstallDrive>:\WF_WCF_Samples

If this directory does not exist, go to (download page) to download all Windows Communication Foundation (WCF) and WF samples. This sample is located in the following directory.

<InstallDrive>:\WF_WCF_Samples\WF\Basic\Persistence\BuiltInConfiguration

Sample Details

This sample consists of a workflow that implements a counting service. Once the service's start method is invoked, the service counts from 0 to 59. The counter is incremented once every 2 seconds. After each count, the workflow persists.

The counting workflow is self-hosted by a workflow service host. The program's Main method creates an instance of the workflow service host that hosts the counting workflow. It defines the endpoints under which the counting workflow can be reached. After that, it defines a SQL workflow instance store behavior, which is used to configure the SQL workflow instance store. Next, the program creates a client that calls the start method of the counting workflow.

Once the program is started, the counter automatically starts counting. Note that it might take a few seconds to load the instance and configure the SQL workflow instance store. For more information about the workflow instance store, see SQL Workflow Instance Store.

The sample consists of two parts:

  1. InstanceStore1 shows how SqlWorkflowInstanceStore is configured using C# code (see Program.cs).

  2. InstanceStore2 shows how SqlWorkflowInstanceStore is configured using XML (see App.config).

The following settings are available to configure the SQL Workflow Instance Store behavior:

  • Set the HostLockRenewalPeriod. This time defines the interval with which the host renews the ownership lock of the instances it runs. The lock information is stored in the Instance Store. If the ownership is not renewed for two of the intervals defined in HostLockRenewalPeriod, the instance is considered abandoned. If another WorkflowServiceHost is running the same workflow and connected to the same instance store (either on the same computer or a different computer), it recovers that instance. (Instance Recovery is out of scope for this sample.)

  • Set the RunnableInstancesDetectionPeriod. This period defines the interval in which the host polls for instances that have become runnable. Instances may become runnable if any of the following events occur:

    • A Durable Timer (Delay) expires.

    • Another host misses its HostLockRenewal heartbeat (for example, due to a computer crash) and the instance is recovered.

  • Set the InstanceCompletionAction. This property, if set to DeleteNothing, keeps completed instances in the Instance Store; if set to DeleteAll, instances are deleted from the store upon completion. Note that

    Note

    Terminating the host by pressing ENTER before the counting has completed does not complete the workflow instance.

  • Set the InstanceLockedExceptionAction. This setting defines what a host should do if it wants to load an instance that is locked by another host. The following options exist:

    • If set to NoRetry: Do not retry the load and return an InstanceLockedException to the host.

    • If set to BasicRetry: Keep retrying to load the instance. The retries are scheduled according to a simple linear algorithm (for example, retry every 5 seconds).

    • If set to AggressiveRetry: Keep retrying to load the instance. The retries are scheduled according to an aggressive exponential back-off algorithm.

  • Set the Encoding option. This setting defines how the instance state is stored in the SQL Workflow Instance Store. The following options exist:

    • The instance state is compressed using the GZip compression algorithm.

    • The instance state is not compressed.

To use this sample

  1. Open a Visual Studio 2010 command prompt as an Administrator if permissions are available.

  2. Navigate to the sample directory (\WF\Basic\Persistence\BuiltInConfiguration\CS) and run CreateInstanceStore.cmd.

  3. If Administrator privileges are not available, Create SQL Server login. Go to Security, Logins. Right-click Logins and create a new login.

  4. Add your ACL user to SQL role. Open Databases, InstanceStore, Security. Right-click Users and select New users. Set the Login name to the user created in the previous step. Add the user to the Database role membership System.Activities.DurableInstancing.InstanceStoreUsers (and others). Note that the user might exist already (for example, user dbo).

  5. Open the InstanceStore.sln file in Visual Studio 2010 and build the solution by pressing CTRL+SHIFT+B.

  6. In Windows Explorer, navigate to the sample’s appropriate bin\debug directory (\WF\Basic\Persistence\BuiltInConfiguration\cs\InstanceStore(1 or 2)\bin\debug), right click InstanceStore.exe and select Run as administrator. This sample must be run with administrative privileges because it opens a channel listener.

  7. If you created the instance store in a database other than a local installation of SQL Server Express you must update the database connection string (const string ConnectionString in Program.cs of the InstanceStore1 project, and the connectionString attribute in App.config of the InstanceStore2 project) in the sample and recompile the sample.

To verify the sample is running correctly

  1. While the sample is running, start SQL Server Management Studio.

  2. In the Object Explorer, select Databases, InstanceStore, Tables, and then System.Activities.DurableInstancing.InstanceTable.

  3. Right click InstanceTable and select Select Top 1000 Rows.

  4. Observe that there is a new entry and that the Lock Expiration changes every 5 seconds, (click the taskbar’s Execute button to refresh the query). This is a consequence of setting the Host Lock Renewal Period to 5.

  5. Observe after the counting completes, that the entry in the instance table is removed. This is a consequence of setting Instance Completion Action to DeleteAll.

  6. Press ENTER to terminate the workflow host application and observe that the LockOwnersTable is deleted.

To uninstall the sample

  1. Run RemoveInstanceStore.cmd in the sample directory (\WF\Basic\Persistence\BuiltInConfiguration).
Ee622978.Important(en-us,VS.100).gif Note:
The samples may already be installed on your computer. Check for the following (default) directory before continuing.

<InstallDrive>:\WF_WCF_Samples

If this directory does not exist, go to Windows Communication Foundation (WCF) and Windows Workflow Foundation (WF) Samples for .NET Framework 4 to download all Windows Communication Foundation (WCF) and WF samples. This sample is located in the following directory.

<InstallDrive>:\WF_WCF_Samples\WF\Basic\Persistence\BuiltInConfiguration

See Also

Other Resources

AppFabric Hosting and Persistence Samples