How to clear an incorrect "This workbook is currently being edited by <user name>" warning.

Symptom

Attempting to open a workbook shows the following warning message: This workbook is currently being edited by <user name>. Changes might result in modification and undo/redo conflicts 
The message is shown even when it has been confirmed that no one else has this workbook open.

Cause

• The undo/redo feature for Workbooks requires validation of whether the Workbook is being edited by more than one user.  
• Any operation performed on a Workbook gets logged to the undo/redo list. If there would be entries added to this list from two different users on the same Workbook, the warning message appears.
• All undo/redo actions are stored in memory.
• The flag indicating concurrent editing can get stuck in memory for a number of reasons, for example if a user's browser session is terminated unexpectedly.  This will cause the warning even when another user has already closed the artifact.

Solution

The Workbook Undo Memory Metrics section can be found within the <datameer host>:<port>/dev page.  This section shows how many users are currently working on Workbooks. There is also the Save & Update button under the Configuration section of this page. It allows configuring undo/redo logging parameters. When this button is clicked, Datameer refreshes all undo/redo metrics including the edited by someone else flag.

This functionality can be used to clear the incorrect warning. But it is very important to keep in mind that this action deletes all undo/redo history.  Extreme care should be taken to ensure users who are currently working on Workbooks are not impacted.

The recommended course of action is as follows:

1. Determine a time period when no users are working with Workbooks to avoid issues due to the undo/redo actions cleanup.
2. Navigate datameer/dev -> Workbook Undo Memory Metrics  page.
3. Press theSave & Update button and refresh the page to ensure that all the counts are reset.