I think it sounds like a great idea! I do have a question on this
approach though out of curiosity.
How would this method handle assets (textures for instance) that are
referenced on two different objects (or perhaps referenced inside the
object's inventories) that are essentially the same but have different
UUIDs? For instance, Object A is a house and has a wallpaper texture
with a UUID b8982190-6537-11e1-b86c-0800200c9a66 and Object B is
different house that uses the same exact wallpaper texture (Shares the
same hash) but has a UUID of 5fa5c9f6-448f-4c9b-8d32-75f226b2173c. Would
de-duplication destroy one of the assets, resulting in one of the houses
to have no texture?
An example of this situation arising would be if hypothetically I were
to build something on another grid using full perm and open licensed
textures and then export my creation using Imprudence for instance which
if all the permissions, creator name, and grid conditions are satisfied
will also export the textures with it, and then import to OpenSim using
its automatic texture upload and texture reassigning capabilities to
recreate my object with all textures intact. If these assets already
exist in the database at the time of upload (perhaps I've created and
imported something else earlier back that uses assets that share the
same hash but not the same UUID) will the newly created object be
missing textures?
Would there be an option in the configuration files for one to turn this
feature off if needed, perhaps to avoid the above scenario?
On 3/2/2012 8:51 PM, Justin Clark-Casey wrote:
Hi folks. As we know, the space required for asset storage in
OpenSimulator grows continuously over time.
I think this is inevitable in a web-like virtual world - distributed
garbage collection is practically impossible. However, the current
OpenSimulator asset service stores much more data than it needs to
since it fails to identify assets that are exact duplicates of each
other.
Previous work in places such as OSGrid, which now uses Dave Coyle's
Simple Ruby Asset Service (SRAS) [1], reveals that preventing
duplicate assets has a significant effect on storage requirements (I
can't remember the exact figures but I think that it's >30%).
Therefore, I propose to introduce a new core asset service
(xassetservice) that will implement asset de-duplication via asset
data hashing. This has already been shown to work by SRAS. I regard
this feature as critical for future plans to extend IAR loading and to
improve the 3-months-out-of-the-box OpenSimulator experience. It does
not aim to replace external projects such as SRAS for heavy users.
I already have a working implementation in the xassetservice git
branch (configuration instructions at [2]). This should not be used
in way except for testing - it is still in the prototype stage and can
change at any time. Only a MySQL implementation exists right now.
The plan would be to have xassetservice exist alongside and
independent of the existing asset service. Only one service can be
used at a time and this is determined via config files. After
considerable testing, xassetservice would become the default asset
service for new OpenSimulator installations. The existing asset
service would continue alongside for a very, very, very long time.
Since asset datasets are so large and critical there would be no
automatic migration between assetservice data and xassetservice.
Instead, there would be an external migration tool.
I may also take this opportunity to implement other asset service
features, such as data storage on disk instead of database (possibly
nicking stuff from kcozen's previous patch for this) and maybe
compression (though I'm currently thinking that the cons of this
outweight the pros).
More detail is at [3]. Comments or alternative implementation
suggestions from developers, etc., are welcome.
[1] https://github.com/coyled/sras
[2]
http://opensimulator.org/wiki/Feature_Proposals/Deduplicating_Asset_Service#Testing
[3]
http://opensimulator.org/wiki/Feature_Proposals/Deduplicating_Asset_Service
--
OpenSim: 9 Region Standalone on 0.7.3 Dev
Physics: Open Dynamics Engine
OS: Windows 7 (x64)
CPU: AMD Phenom II X4 840 3.2 GHz
Memory: 11 GB DDR3
Database: MySQL 5.1.11
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