Question

I have the following code which lets me execute a workflow. This could be called repeatedly. And often is. It’s also living in a webservice, so there could be multiple calls to it at the same time. This currently works. But it’s slow, since instantiating a WorkflowRuntime each time is very slow.

How can I improve this?

public class ApprovalWorkflowRunner : IApprovalWorkflowRunner
{
    private static ILogger Logger { get; set; }
    private static IRepository Repository { get; set; }

    public ApprovalWorkflowRunner(ILogger logger, IRepository repository)
    {
        Logger = logger;
        Repository = repository;
    }

    public Request Execute(Action action)
    {
        var request = new Request();

        using (var workflowRuntime = new WorkflowRuntime())
        {
            workflowRuntime.StartRuntime();
            var waitHandle = new AutoResetEvent(false);
            workflowRuntime.WorkflowCompleted += ((sender, e) =>
                                                    {
                                                        waitHandle.Set();
                                                        request = e.OutputParameters["gRequest"] as Request;
                                                    });
            workflowRuntime.WorkflowTerminated += ((sender, e) =>
                                                    {
                                                        waitHandle.Set();
                                                        Logger.LogError(e.Exception, true, action.Serialize());
                                                    });

            var parameters = new Dictionary<string, object>
                                {
                                    {"RepositoryInstance", Repository},
                                    {"RequestID", action.RequestID.ToString()},
                                    {"ActionCode", action.ToString()}
                                };

            var instance = workflowRuntime.CreateWorkflow(typeof (ApprovalFlow), parameters);
            instance.Start();
            waitHandle.WaitOne();
        }

        return request;
    }
}

Ideally, I’d like to keep one copy of the WorkflowRuntime around. But since I’m passing other objects around in the CreateWorkflow function and WorkflowCompleted event, I don’t see how it would work.

…am I missing something simple here, there’s a good chance my brain didn’t tell my body it wasn’t showing up to work today.

Answer 1

One runtime can run many workflows at the same time. As per the answer here:

That page shows some code for a WorkflowRuntime factory that I will include below, that I believe was originally taken from the Windows Workflow Foundation Step by Step Book

public static class WorkflowFactory
{
    // Singleton instance of the workflow runtime
    private static WorkflowRuntime _workflowRuntime = null;

    // Lock (sync) object
    private static object _syncRoot = new object();

    /// <summary>
    /// Factory method
    /// </summary>
    /// <returns></returns>
    public static WorkflowRuntime GetWorkflowRuntime()
    {
        // Lock execution thread in case of multi-threaded
        // (concurrent) access.
        lock (_syncRoot)
        {
            // Check for startup condition
            if (null == _workflowRuntime)
            {
                // Provide for shutdown
                AppDomain.CurrentDomain.ProcessExit += new EventHandler(StopWorkflowRuntime);
                AppDomain.CurrentDomain.DomainUnload += new EventHandler(StopWorkflowRuntime);

                // Not started, so create instance
                _workflowRuntime = new WorkflowRuntime();

                // Start the runtime
                _workflowRuntime.StartRuntime();
            } // if

            // Return singleton instance
            return _workflowRuntime;
        } // lock
    }

    // Shutdown method
    static void StopWorkflowRuntime(object sender, EventArgs e)
    {
        if (_workflowRuntime != null)
        {
            if (_workflowRuntime.IsStarted)
            {
                try
                {
                    // Stop the runtime
                    _workflowRuntime.StopRuntime();
                }
                catch (ObjectDisposedException)
                {
                    // Already disposed of, so ignore...
                } // catch
            } // if
        } // if
    }
}

You would simply call

WorkflowFactory.GetWorkflowRuntime();

EDIT:
OK sorry. You can try checking the instance is the one you expect, and returning if it’s not. Please note this code is untested, just trying to get the idea across.

public class ApprovalWorkflowRunner : IApprovalWorkflowRunner
{
    private static ILogger Logger { get; set; }
    private static IRepository Repository { get; set; }

    public ApprovalWorkflowRunner(ILogger logger, IRepository repository)
    {
        Logger = logger;
        Repository = repository;
    }

    public Request Execute(Action action)
    {
        var request = new Request();

        var workflowRuntime = WorkflowFactory.GetWorkflowRuntime();

        workflowRuntime.StartRuntime();
        var waitHandle = new AutoResetEvent(false);
        WorkflowInstance instance = null;
        workflowRuntime.WorkflowCompleted += ((sender, e) =>
                                                {
                                                    if (e.WorkflowInstance != instance) return;
                                                    waitHandle.Set();
                                                    request = e.OutputParameters["gRequest"] as Request;
                                                });
        workflowRuntime.WorkflowTerminated += ((sender, e) =>
                                                {
                                                    if (e.WorkflowInstance != instance) return;
                                                    waitHandle.Set();
                                                    Logger.LogError(e.Exception, true, action.Serialize());
                                                });

        var parameters = new Dictionary<string, object>
                            {
                                {"RepositoryInstance", Repository},
                                {"RequestID", action.RequestID.ToString()},
                                {"ActionCode", action.ToString()}
                            };

        instance = workflowRuntime.CreateWorkflow(typeof (ApprovalFlow), parameters);
        instance.Start();
        waitHandle.WaitOne();

        return request;
    }
}