This document summarizes the versioning system used in Graspeo. It discusses: 1) Existing versioning systems like Mercurial and Git and their limitations with media files. 2) Graspeo's solution of creating a new version for each significant modification to an item, space, or resource. 3) How versioning works in Graspeo by creating snapshots of items and storing them in a separate versions collection with links to the original item. 4) The process of restoring an earlier version, including recursively updating item links and contents.

1. Versioning system in
Graspeo
Nikita Grishin, EPFL, 02.06.2014
Supervised by Andrii Vozniuk

3. Motivation
Every document management system
has the versioning.

4. Motivation
Every document management system
has the versioning.
Various resources from various locations
need to be tracked back

5. Motivation
Every document management system
has the versioning.
Various resources from various locations
need to be tracked back
The collaborators system implies the
recovery system

6. State of the art

7. • Mercurial, SVN/CVS!
• On document change, only modifications are saved
• Easy to track modifications
• Difficult to recover old versions
• Git
• On file change, new version of file is created
• Easy to recover old versions
• Difficult to track modifications

8. • Mercurial, SVN/CVS!
• On document change, only modifications are saved
• Easy to track modifications
• Difficult to recover old versions
• Git
• On file change, new version of file is created
• Pointer to the last version
• Easy to recover old versions
• Difficult to track modifications
Only for text documents.
Works very bad with media content.

9. • Snapshots: new version of document for each
modification

10. • Snapshots: new version of document for each
modification
• Recovering the older version: creates a copy of the
asked version on the top of the last version

11. • Snapshots: new version of document for each
modification
• Recovering the older version: creates a copy of the
asked version on the top of the last version
• Some old versions can be removed by Google in
case of lack of space

12. • Snapshots: new version of document for each
modification
• Recovering the older version: creates a copy of the
asked version on the top of the last version
• Some old versions can be removed by Google in
case of lack of space
• Only users that can edit the document can see its
modification history

13. • Hard drive snapshots.
Apple TimeMachine

14. • Hard drive snapshots.
• Keeps:
• Hourly backups for last 24 hours
Apple TimeMachine

15. • Hard drive snapshots.
• Keeps:
• Hourly backups for last 24 hours
• Daily backups for the past month
Apple TimeMachine

16. • Hard drive snapshots.
• Keeps:
• Hourly backups for last 24 hours
• Daily backups for the past month
• Weekly backups until your backup drive is full.
Apple TimeMachine

17. • Hard drive snapshots.
• Keeps:
• Hourly backups for last 24 hours
• Daily backups for the past month
• Weekly backups until your backup drive is full.
• When your backup drive is full, TimeMachine
removes old backups to free space.
Apple TimeMachine

18. Graspeo versioning system solution
Versioning

19. Graspeo versioning system solution
Versioning
• Snapshots: new version of item for
each significant modification

20. Graspeo versioning system solution
Versioning
• Snapshots: new version of item for
each significant modification
• Significant modification is a
modification that needs to be stored
in versions.
• Space: creation of space,
modification in subitems list
• Resource: creation of resource,
modification of its content (resource
replacement)

21. Graspeo versioning system solution
• Snapshots: new version of item for each
significant modification
• Significant modification is a
modification that needs to be stored in
versions.
• Space: creation of space, modification
in subitems list
• Resource: creation of resource,
modification of its content (resource
replacement)
• Restore a version remains to copy the
content from version document to an item
document. This will automatically create
a new version on the top of versioning
tree.
Versioning

23. How does it work?
• New collection for versions: easy scalable

24. How does it work?
• New collection for versions: easy scalable
• Version document is almost a full copy of item
document

25. How does it work?
• New collection for versions: easy scalable
• Version document is almost a full copy of item
document
• Version creation happens in mongoose post-save
hook

26. How does it work?
• New collection for versions: easy scalable
• Version document is almost a full copy of item
document
• Version creation happens in mongoose post-save
hook
• The versions controller takes a decision if a new
version is needed (i.e. defining a notion of
significant modification)

27. How does it work?
• Resources version:
• GridFS to store old file versions
• The last version of file is also stored on local
filesystem because of performance issues with
GridFS and use of BTSync

28. How does it work?
• Version Schema
• Extends Item schema
• New field called «originId» to track one item
modifications

29. How does it work?
• Version is created on item creation and on
significant modification

30. How does it work?
• Version is created on item creation and on
significant modification
• Space:
• Modification of subitems list (subitem created/
removed)
• Resource replacement

31. How does it work?
• Version is created on item creation and on significant
modification
• Space:
• Modification of subitems list (subitem created/
removed)
• Resource replacement
• Resource:
• Replacement

32. How does it work?
• Versioning API
• List of versions timestamps
• Version by date
• Restore a chosen version of space

33. How does it work?
• Version restore
• User asks to restore the version of space for given date
• System looks for that space in items collection and for
its version in versions collection
• Copies subitems list from version to item document
• Removes all items in items collection that are no more in
recovered space
• Recursively restore subitems of that space

34. How does it work?
• Version restore
• While recursively restoring subitems of space, some of
them can be already removed from items collection. For
that case:
• The system creates a new document in item
collections and fill it with data from version document
• New document = new id: the system fix all path- and
id-related problems
• That is the most expensive part of restoring process

35. How does it work?
• Version restore: Resource
• Make a restore in database as described above
• Write the asked version of resource to disk
• Regenerate thumbnails for the new resource
content.

36. How does it work?
• On the user side:
• Version creation is completely transparent
• Version restore is a little bit slow
• On the server side:
• Version creation is asynchronous and with a low load on
database
• Version restore is expensive in terms of time and
database load

37. Future Plans

38. Future Plans
• Optimize the version restore process
• Extend the current versioning system to a multiuser
versioning
• Integrate Git with current versioning system for text
files
• Create a movie-style visualization of versioning and
modification tracking

39. Thank you for your attention
Questions