[Opensim-dev] Error detection when storing an asset

[Melanie]

The point is no NOT let it fail. Asset storing never fails
permanently if it's retried until successful. The upper layers (all
the way to the viewer) are not equipped to handle an asset storing
failure. Propagating the exception would just annoy the user with
needless messages. Since asset servers can be "gone" for a while,
for instance when there is a net failure, there is no way to give it
a timeout, either. A sim in OSGrid, if it gets disconnected,  could
run on locally cached assets and manage to reconnect after 20
minutes and simply upload all new assets since then. Screaming
"failure" at the user is pointless in such a scenario.

- Melanie

On 18/04/2014 22:56, Oren Hurvitz wrote:
> There seems to be a misunderstanding here. We're talking about a case where
> the operation has FAILED. The only question is whether to pretend that it
> succeeded, so that the user will find out that it failed later, to their
> surprise, or to report failure immediately. Obviously it's better to report
> failure immediately.
> 
> 
> 
> On Fri, Apr 18, 2014 at 10:40 PM, Melanie <melanie at t-data.com> wrote:
> 
>> Name one valid use case where current OpenSim is able to handle such
>> an exception gracefully, e.g. without user-visible error.
>>
>> - Melanie
>>
>> On 18/04/2014 13:28, Mike Chase wrote:
>> > I'm inclined to agree with Oren.  Asset Writes could fail for a variety
>> of
>> > reasons and there are lots of use cases where you need to know the asset
>> is
>> > on disk.  I think propagating exceptions is the more sound approach IMO.
>> >
>> > I also agree re: the custom comms vs a persistent queue mechanism but I
>> > don't want to derail this topic.   That can wait for another day.
>> >
>> > Mike
>> >
>> > -----Original Message-----
>> > From: opensim-dev-bounces at lists.berlios.de
>> > [mailto:opensim-dev-bounces at lists.berlios.de] On Behalf Of Oren Hurvitz
>> > Sent: Friday, April 18, 2014 7:06 AM
>> > To: opensim-dev at lists.berlios.de
>> > Subject: Re: [Opensim-dev] Error detection when storing an asset
>> >
>> > Regarding the hiding of exceptions: to be clear, I was already bitten by
>> > this behavior; that's why I started to investigate how assets are
>> stored. I
>> > have therefore already changed Kitely's version of OpenSim to propagate
>> > exceptions, and the question is whether other people would like me to
>> > contribute this change. If anyone has an opinion then please reply.
>> >
>> > Regarding your suggestion to save assets to local disk and retry them
>> later:
>> > this is basically what a persistent message queue does. If you're going
>> to
>> > go that route then it would be best to add a real message queue rather
>> than
>> > a home-grown one. I would LOVE it if OpenSim used a message queue for
>> > communications, as it would allow ripping out thousands of lines of
>> homemade
>> > communications code, and would be faster and more reliable to boot. But
>> > that's a bigger issue and I'll put it aside for now.
>> >
>> > In this particular case, using a persistent message queue isn't be the
>> right
>> > solution: the right solution is to report failures immediately. Otherwise
>> > you'd get weird behavior such as a user who thinks they've successfully
>> worn
>> > a piece of clothing, but when they teleport to another region it
>> disappears
>> > because the other region can't load the asset (because it was never
>> saved).
>> > To prevent these problems you need to fail-fast, and tell the user
>> > immediately when a problem happens. This doesn't mean to crash the sim; I
>> > strongly doubt any asset failure would cause that, it would just fail the
>> > specific packet or message that is currently being handled, as it should.
>> >
>> >
>> >
>> > --
>> > View this message in context:
>> >
>> http://opensim-dev.2196679.n2.nabble.com/Error-detection-when-storing-an-ass
>> > et-tp7579223p7579225.html
>> > Sent from the opensim-dev mailing list archive at Nabble.com.
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> 
> 
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