Error, "Could not find work queue item . . . the item no longer exists"

Products

• Workflow Solution

Issue/Introduction

The error, "Could not find work queue item XXXXXXXX-XXXX-XXXX-XXXXXXXXXXXX the item no longer exists. Number of items in queue X," appears while debugging a project or in the error log.  (The x's in the error message represent a GUID and a number of items in the queue.)

Environment

Workflow 8.x

Cause

When using branching and merging in Workflow projects, there is always the potential of orphaning processes if the proper components are not used to merge the branched processes back together.  With this particular error, the problem was caused by a component that didn't wait for Dialog Workflow components inside linked models to complete before moving on in the process flow.

We have also seen some problems with certain components (most notably Dialog Workflow) that run into issues with the Wait components when they are copied to another model using copy/paste.  They seem to retain some of the properties of the original and make them indistinguishable to the Wait components.  The end result is that the Wait components will allow the process to complete even though not all of the components have finished.

Resolution

There are three main components that are used to merge process back together.  They have similar names but very different behavior.

• Wait For All Workflow Components (Merge): This component waits for all workflow components to complete in any model in this workflow. You should never use more than one of these in a single project.
• Wait For All Workflow Components In Model (Merge): This component waits for all workflow components to complete in the current model in this workflow.
• Wait For Specified Workflow Components In Model (Merge): This component waits for specific workflow components within your model to complete execution.

In the case of the "Could not find work queue item" error, the user had used "Wait For All Workflow Components In Model (Merge)" despite the fact that there were several linked models that had Dialog Workflows pending. This created an issue when single branches were completing and reaching this component. Since this component only looks at the current model, it would not see the pending Dialog Workflows inside the models. The process completed prematurely and caused the error to be generated.  In this situation, the "Wait For All Workflow Components (Merge)" should be used.

If this problem is being caused by the copy/paste problem, any components that were created with copy/paste should be deleted and a fresh copy of the component needs to be dragged over from the Toolbox.