CODEWITHSUNDEEP
persistenceworkflow-foundation-4
rekna
rekna

Reputation: 5333

WF4 InstancePersistenceCommand interrupted

I have a windows service, running workflows. The workflows are XAMLs loaded from database (users can define their own workflows using a rehosted designer). It is configured with one instance of the SQLWorkflowInstanceStore, to persist workflows when becoming idle. (It's basically derived from the example code in \ControllingWorkflowApplications from Microsoft's WCF/WF samples).

But sometimes I get an error like below:

System.Runtime.DurableInstancing.InstanceOwnerException: The execution of an InstancePersistenceCommand was interrupted because the instance owner registration for owner ID 'a426269a-be53-44e1-8580-4d0c396842e8' has become invalid. This error indicates that the in-memory copy of all instances locked by this owner have become stale and should be discarded, along with the InstanceHandles. Typically, this error is best handled by restarting the host.

I've been trying to find the cause, but it is hard to reproduce in development, on production servers however, I get it once in a while. One hint I found : when I look at the LockOwnersTable, I find the LockOnwersTable lockexpiration is set to 01/01/2000 0:0:0 and it's not getting updated anymore, while under normal circumstances the should be updated every x seconds according to the Host Lock Renewal period...

So , why whould SQLWorkflowInstanceStore stop renewing this LockExpiration and how can I detect the cause of it?

Upvotes: 3

Views: 6396

Answers (3)

Marco Zecca
Marco Zecca

Reputation: 57

This is an old thread but I just stumbled on the same issue.

Damir's Corner suggests to check if the instance handle is still valid before calling the instance store. I hereby quote the whole post:

Certain aspects of Workflow Foundation are still poorly documented; the persistence framework being one of them. The following snippet is typically used for setting up the instance store:

var instanceStore = new SqlWorkflowInstanceStore(connectionString);
instanceStore.HostLockRenewalPeriod = TimeSpan.FromSeconds(30);
var instanceHandle = instanceStore.CreateInstanceHandle();
var view = instanceStore.Execute(instanceHandle, 
    new CreateWorkflowOwnerCommand(), TimeSpan.FromSeconds(10));
instanceStore.DefaultInstanceOwner = view.InstanceOwner;

It's difficult to find a detailed explanation of what all of this does; and to be honest, usually it's not necessary. At least not, until you start encountering problems, such as InstanceOwnerException:

The execution of an InstancePersistenceCommand was interrupted because the instance owner registration for owner ID '9938cd6d-a9cb-49ad-a492-7c087dcc93af' has become invalid. This error indicates that the in-memory copy of all instances locked by this owner have become stale and should be discarded, along with the InstanceHandles. Typically, this error is best handled by restarting the host.

The error is closely related to the HostLockRenewalPeriod property which defines how long obtained instance handle is valid without being renewed. If you try monitoring the database while an instance store with a valid instance handle is instantiated, you will notice [System.Activities.DurableInstancing].[ExtendLock] being called periodically. This stored procedure is responsible for renewing the handle. If for some reason it fails to be called within the specified HostLockRenewalPeriod, the above mentioned exception will be thrown when attempting to persist a workflow. A typical reason for this would be temporarily inaccessible database due to maintenance or networking problems. It's not something that happens often, but it's bound to happen if you have a long living instance store, e.g. in a constantly running workflow host, such as a Windows service.

Fortunately it's not all that difficult to fix the problem, once you know the cause of it. Before using the instance store you should always check, if the handle is still valid; and renew it, if it's not:

if (!instanceHandle.IsValid)
{
    instanceHandle = instanceStore.CreateInstanceHandle();
    var view = instanceStore.Execute(instanceHandle, 
        new CreateWorkflowOwnerCommand(), TimeSpan.FromSeconds(10));
    instanceStore.DefaultInstanceOwner = view.InstanceOwner;
}

It's definitely less invasive than the restart of the host, suggested by the error message.

Upvotes: 1

Rady
Rady

Reputation: 918

This happens because there are procedures running in the background and trying to extend the lock of the instance store every 30 seconds, and it seems that once the connection fail connecting to the SQL service it will mark this instance store as invalid. you can see the same behaviour if you delete the instance store record from [LockOwnersTable] table. The proposed solution is when this exception fires, you need to free the old instance store and initialize a new one 

public class WorkflowInstanceStore : IWorkflowInstanceStore, IDisposable
{
    public WorkflowInstanceStore(string connectionString)
    {
        _instanceStore = new SqlWorkflowInstanceStore(connectionString);

        InstanceHandle handle = _instanceStore.CreateInstanceHandle();
        InstanceView view = _instanceStore.Execute(handle, 
            new CreateWorkflowOwnerCommand(), TimeSpan.FromSeconds(30));
        handle.Free();

        _instanceStore.DefaultInstanceOwner = view.InstanceOwner;
    }

    public InstanceStore Store
    {
        get { return _instanceStore; }
    }

    public void Dispose()
    {
        if (null != _instanceStore)
        {
            var deleteOwner = new DeleteWorkflowOwnerCommand();
            InstanceHandle handle = _instanceStore.CreateInstanceHandle();
            _instanceStore.Execute(handle, deleteOwner, TimeSpan.FromSeconds(10));
            handle.Free();
        }
    }

    private InstanceStore _instanceStore;
}

you can find the best practices to create instance store handle in this link Workflow Instance Store Best practices

Upvotes: 1

khaled Dehia
khaled Dehia

Reputation: 947

you have to be sure about expiration of owner user

here how I am used to handle this issue 

     public SqlWorkflowInstanceStore SetupSqlpersistenceStore()
    {
        SqlWorkflowInstanceStore sqlWFInstanceStore = new SqlWorkflowInstanceStore(ConfigurationManager.ConnectionStrings["DB_WWFConnectionString"].ConnectionString);
        sqlWFInstanceStore.InstanceCompletionAction = InstanceCompletionAction.DeleteAll;
        InstanceHandle handle = sqlWFInstanceStore.CreateInstanceHandle();
        InstanceView view = sqlWFInstanceStore.Execute(handle, new CreateWorkflowOwnerCommand(), TimeSpan.FromSeconds(30));
        handle.Free();
        sqlWFInstanceStore.DefaultInstanceOwner = view.InstanceOwner;
        return sqlWFInstanceStore;
    }

and here how you can use this method 

     wfApp.InstanceStore = SetupSqlpersistenceStore();

wish this help

Upvotes: 0

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