[Opensim-dev] Updating attachment assets

[Justin Clark-Casey]

On 03/10/11 07:54, Oren Hurvitz wrote:
> Thanks for that info! Indeed it's unsafe to delete assets in the scenario
> that I've described. It looks like it's not safe to delete assets at all
> (except for trivial assets such as map tiles) unless we add some form of
> reference-counting or garbage collection, since any asset might be in use in
> other peoples' inventories, or in a prim in some other region.
>
> Suppose I want to implement garbage collection of unused assets. I would
> need to find which assets are in use anywhere. Would the following procedure
> be sufficient? :
>
> 1. Find all the assets in the inventories of all the users
> 2. Find all the assets in the inventories of all the prims
> 3. Parse each asset to find if the asset itself points to other assets (use
> UuidGatherer)
>
> Is there any other place that uses assets?

Terrain textures is one, as seen in ArchiveWriteRequestPreparation.ArchiveRegion().  I can't think of another one off-hand.

Needless to say, distributed garbage collection is extremely hard.  I don't think that a reference counting approach is 
feasible.  Recording access times is also problematic since a simulator may have the asset cached for a very long time.

There are some low-ish hanging fruit for retraining asset growth if you haven't already picked them.  coyled's SRAS [1] 
does asset de-duplication, compression and stores assets on the filesystem rather than as binary db blobs, which 
apparently helps a lot.  This is the kind of thing that should also be in the core asset service.

[1] https://github.com/coyled/sras

>
> Oren
>
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Justin Clark-Casey (justincc)
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