Connecting back up to a long running Workflow through a web service
Posted
Friday, October 06, 2006 5:11 PM
by
Maurice
When we start a workflow instance through a web service we might need to call it a second time. No big deal, all we need to do is add a second WebServiceInputActivity with a matching WebServiceOutputActivity to the workflow and we are good to go. However when we try to call the second method from our client we get the following error:
Server was unable to process request.
Current session has no workflow instance associated with it.
Well that is because the workflow engine adds a cookie named WF_WorkflowInstanceId to the response used to connect the second call to the same workflow. Alright the solution is simple; add the following to the web service before the first call:
workflows.CookieContainer = New CookieContainer()
Now everything works like a charm.
But suppose this is a long running workflow and we need to communicate with the same workflow a day later. We can hardly keep the proxy and cookie container in memory all this time. Well again the trick is simple, just save the details from the cookie, the Name, value, path and the domain and uses these to recreate the cookie next day.
Example client code:
Imports System.Net
Module Module1
Private _cookieName AsString
Private _cookieValue AsString
Private _cookiePath AsString
Private _cookieDomain AsString
Sub Main()
SubmitExpenses()
GetStatus()
Console.ReadLine()
EndSub
''' <summary>
''' Day one, submit the expenses.
''' </summary>
''' <remarks></remarks>
PrivateSub SubmitExpenses()
Dim workflows AsNew workflows.Workflow1_WebService
workflows.CookieContainer = New CookieContainer()
workflows.Submit("Holiday", 1000.0)
' Save the cookie info for next request
Dim cookie As Cookie
cookie = workflows.CookieContainer.GetCookies(New Uri(workflows.Url))(0)
_cookieName = cookie.Name
_cookiePath = cookie.Path
_cookieValue = cookie.Value
_cookieDomain = cookie.Domain
EndSub
''' <summary>
''' Day two, come back and find its aproved :-)
''' </summary>
''' <remarks></remarks>
PrivateSub GetStatus()
Dim workflows As workflows.Workflow1_WebService
workflows = New workflows.Workflow1_WebService
workflows.CookieContainer = New CookieContainer()
Dim cookie AsNew Cookie(_cookieName, _cookieValue, _cookiePath, _cookieDomain)
workflows.CookieContainer.Add(cookie)
Console.WriteLine(workflows.GetStatus())
EndSub
EndModule
Enjoy!