For most problems with the Gallery snapshot problem, there are entries in the ULS – but sometimes there are no items or if there are, there is just the “Timeout Exception”. Under these circumstances there is so little to go on that it is hard to figure out how to even get started. Here are some of the general ‘how to get started’ recommendations that I have:
- First and most importantly, the rendering engine for the entry must be running.
- For workbooks, Excel Services must be running. The way that snapshots are taken is that a web browser is brought up by the GetSnapshot.exe process and inserted into the document library as a collection of images (representing the worksheets in the workbook).
- For reports, Reporting Services must be running in SharePoint integrated mode so that the .rdl files can be rendered in a browser.
- Go into the site collection and look to see if the PowerPivot feature is enabled.
- Sometimes you will find that it is disabled. Typically this happens if the user starts from the “Blank” Site template. For most templates, such as the Team Site, we use feature stapling so that the PowerPivot feature is automatically enabled. However the Blank Site is specifically designed by SharePoint as having all features disabled. So if the end-user starts with the Blank Site and then adds a PowerPivot Gallery (which is a document library), you will find that snapshots will just never happen.
- Sometimes even if the PowerPivot feature is enabled, sometimes the SharePoint event handler just stops firing. The GetSnapshot.exe process is started from the Gallery event handler (when a new document is added or if an existing document is being updated). If GetSnapshot.exe isn’t being started (see http://powerpivotgeek.com/2010/10/24/snapshots-not-being-taken/ for another reason why it might not be started, but at least it had an error being recorded) then it could be an issue with the event handler. The workaround that we have found works is to deactivate and then re-enable the PowerPivot site collection level feature.
- Look to see if GetSnapshot.exe process starts. If it does, the ULS should contain something, even if it just a Timeout Exception. If this is happening:
- Gallery should set the doclib advanced setting "Opening documents in the browser" from "Use the system default" to "Open in the browser" – we are finding that when some apps are installed on SharePoint, that the default value is being changed to “Open in client application”
- If all else fails, log onto the server interactively using the web application app pool service account. Then try to view the file that you are having problems with. As the first item above mentions, the rendering engine must be working. It may be that there are issues with the web application app pool service account that is stopping the browser control from rendering the content.
Hope this helps.