jump to navigation

OpenSim Tech Basics: OpenSim is brought to you by the letters U, G, A, I and R April 17, 2008

Posted by justincc in opensim, opensim-dev, opensim-tech-basics, secondlife.

Hello there. This is the first in an irregular series of articles about some of the technological basics of OpenSim. Please feel free to suggest further topics in the comments, though as OpenSim is already large enough to make it difficult for a single person to understand, I might only be able to talk about a small proportion of them :). This means I also take no responsibilty for the accuracy of these articles – even if they are correct right now, the rapid evolution of OpenSim might very quickly make them invalid.

I will be assuming a certain amount of OpenSim and general technical knowledge, though I hope to keep this to a minimum.

Anyway, today I want to talk about the letters U, G, A, I and R (also known as S). Apologies for the crappy graphics, by the way.

Don’t worry – I’m not going to launch into some extended Sesame Street metaphor. Rather. these letters represent the different ‘services’ in OpenSim. In order,

* U is the user service. This primarily handles user logins and logouts. This means that the user needs to be authenticated, and the region which is going to receive them needs to be told that they are coming.

* G is the grid service. When OpenSim is in a grid configuration (which we’ll talk about later on), it handles the registration of region servers with the grid, and is responsible for telling regions about their immediate neighbours. It also handles some of the main map functionality (which doesn’t work all that well at the moment).

* A is the asset service. This is a simple service which just retrieves and stores asset data (scripts, textures, sounds, etc).

* I is the inventory service. This is the service responsible for storing and updating your inventory folders and items.

* R is the region service (or Sim service). This is the big one – it contains orders of magnitude more code than all the other services. As you can probably guess, it’s responsible for actually providing an OpenSim region – so its major roles include handling the client sessions, managing the 3d environment and running scripts. It’s also responsible for telling a neighbouring region that an avatar is on its way when you cross a region border.

So why am I calling these things services rather than servers? This relates to the fact that OpenSim can be run in two configurations, standalone (or sandbox) and grid. In standalone mode, all these services are run as local code in the OpenSim executable. So when you open a script in a prim inventory, for instance, your client thread runs directly through the inventory code to find the asset UUID, then runs through the asset code to retrieve the script itself (ultimately from your local database). However, if you’re running on a region server in grid mode, the same action will

1. Query the local inventory information cache for the asset UUID. The cached information was itself retrieved from the grid inventory server when you entered the region.

2. Query the local asset cache for the asset. If the asset is there, it is returned directly. If the asset is a texture and it isn’t there, then we send ask the asset server for it and place the request on a queue. Once the asset server gives us the data, we take the queued request and use it to send the texture data back to the client. If the asset is not a texture, I have a suspicion we just wait a while to see if it comes in, rather than queueing the request (which is what we should be doing).

So as you can appreciate, what goes on in grid mode is rather more complicated than what goes on in standalone! And this is a major reason why grid mode can be rather unstable with our current alpha codebase. For instance, if when you cross into a region the inventory server fails to deliver your inventory and you then open a folder in your client’s inventory, the region server may tell you that there is nothing in that folder – it might seem that all your items have ‘disappeared’! If you then create new items on that region, there’s then a good chance that they won’t be properly stored in your inventory, and the next time you login, they will have disappeared. This problem is compounded by the fact that the Linden client caches the inventory, so unless you clear your cache – those items may seem to have disappeared permanently (even though they haven’t). We actually hope to address some of these problems soon (probably by popping up a big fat textbox telling you that your inventory has failed and that you need to relog :).

Also, the current configuration of services, and perhaps the basics of the service architecture, will almost certainly change in the future. At the moment, we’re running with something called Open Grid Services 1 (OGS1). This is the first iteration of OpenSim’s grid and inter-region communications standard. However, Michael Wright (or MW), our dear founder, often talks about the need for an OGS2 (or possibly an OGS1.5). I don’t think there’s a firm idea yet of what this will contain, but among possible candidates are changes to make it easier to register custom services (not the U, G, A, I and R that OpenSim has pre-defined), and a move to abstract the standard away from the underlying communications transport.

As ever, watch this space!



1. OpenSim Tech Basics : My God, it’s full of modules! « justincc’s opensim blog - May 8, 2008

[…] or provide extensions to the existing codebase. If one doesn’t count alternative grid service implementations, all the modules which I know to currently exist come bundled with OpenSim (such as […]

2. Why I love OSGrid « justincc’s opensim blog - May 23, 2008

[…] and can be flown/teleported into and out of just like any other region.  All the common grid services (currently user, grid map, asset and inventory) are provided by central OpenSim grid servers run by […]

3. This Week in OpenSim Dev - week ending Saturday 7th June 2008 « justincc’s opensim blog - June 8, 2008

[…] this functionality you will need to startup the new Messaging Server in addition to the current UGAI servers […]

4. Jamie - December 20, 2012

There is certainly a great deal to find out about this subject.

I love all the points you have made.

5. Arbors - January 25, 2013

Hello there! Do you know if they make any plugins to help with SEO?
I’m trying to get my blog to rank for some targeted keywords but I’m not seeing very good success.
If you know of any please share. Appreciate it!

6. Immigration Advicers in kingston upon thames - February 28, 2013

I am regular reader, how are you everybody?
This piece of writing posted at this web page is truly nice.

7. HDR Tutorial - March 15, 2013

Hi! I know this is kind of off topic but I was wondering if you knew where I could find a captcha plugin for my comment form?

I’m using the same blog platform as yours and I’m having
problems finding one? Thanks a lot!

8. Sam - March 15, 2013

On this blog post you go through a bunch of
of the most important views!!
Simple to read through and including interesting
Thank you for sharing OpenSim Tech Basics: OpenSim is brought to
you by the letters U, G, A, I and R | justincc’s opensim blog!

9. Recruitment Consultant in Darlington - March 16, 2013

Thank you for your fantastic post! It has long been really beneficial.
I hope that you will proceed sharing your wisdom with

10. Federico - March 17, 2013

Terrific post but I was wondering if you could write
a little more on this topic? I’d be very thankful if you could elaborate a little bit further. Many thanks!

11. online coupon - May 7, 2013

This is my first time pay a visit at here and i am truly
pleassant to read all at alone place.

12. how to draw portraits - May 27, 2013

I don’t even know the way I stopped up here, however I assumed this submit was good. I do not know who you might be however definitely you are going to a famous blogger in case you are not already. Cheers!

13. learn to draw anime - May 27, 2013

I think this is one of the most important information for me.
And i am glad reading your article. But wanna remark on few general things, The website style is wonderful, the
articles is really great : D. Good job, cheers

14. international business articles - June 3, 2013

If you desire to improve your know-how only keep visiting this website and be
updated with the latest news update posted here.

15. profit forex signals review - July 11, 2013

Howdy! I know this is kinda off topic however , I’d figured I’d ask.
Would you be interested in exchanging links or maybe
guest writing a blog post or vice-versa? My site discusses a
lot of the same topics as yours and I feel we could greatly benefit from each other.
If you’re interested feel free to send me an e-mail. I look forward to hearing from you! Terrific blog by the way!

16. Free Mofos Passwords - January 9, 2014

A number of adult film actors also offer web sites and movies on
the net. Many of these superstars get this amazing following, and also
fans can keep up with the most recent news of their favorites having
interviews around the sites, and have a very source of purchasing products like movies endorsed by
a well liked adult mature stars.

17. العاب حربيه - April 2, 2014

You actually make it seem so easy together with your presentation but
I in finding this matter to be actually something which
I think I might by no means understand. It kind of feels too
complex and extremely broad for me. I’m having a look ahead in your
next publish, I will try to get the hang of it!

18. network colleges affiliate marketing - May 27, 2014

Excellent post. I was checking continuously this blog and I’m impressed!
Very helpful information particularly the last part 🙂 I care for such information a lot.
I was seeking this particular info for a very long time.
Thank you and good luck.

19. affiliate programs videos - June 6, 2014

You are my aspiration , I have few blogs and sometimes run out from to brand.

20. uses of nebulizer machine - July 15, 2014

And with efficient thermal properties some drape shops simply repatternise nebulizer machine them
and keep their measurements separate from each other.
Silk, velvet, linen, or cotton nebulizer machine fabric.
Curtains can come in strips, polka dots or stripes, and
get it blown up to a poster size. Cafe style net curtains: Though this design is often used for
tailored curtains? Every person has seen one, mainly because tab top curtains have been recognised as a mark of fortune and prosperity.

21. Lucile - July 22, 2014

Hello! Do you know if they make any plugins to help with SEO?
I’m trying to get my blog to rank for some targeted keywords but I’m not seeing very good success.
If you know of any please share. Thank you!

22. Wilmer - September 13, 2014

This is really fascinating, You’re an excessively skilled blogger.

I’ve joined your feed and look forward to looking for more of your wonderful post.
Additionally, I have shared your web site in my social networks

23. Computer - September 21, 2014

If you are going for finest contents like I do, simply go
to see this website all the time as it offers feature
contents, thanks

24. 30th birthday ideas - September 21, 2014

Thanks , I’ve recently been searching for information approximately this subject for a long time and yours
is the greatest I have discovered till now. But, what about the conclusion? Are you sure about
the supply?

25. http://code-promo-amazon.blogspot.com - September 26, 2014

First off I would like to say awesome blog!

I had a quick question which I’d like to ask if you don’t mind.
I was curious to know how you center yourself and clear your mind
before writing. I have had a hard time clearing my thoughts in getting
my thoughts out there. I do enjoy writing however it just seems like the
first 10 to 15 minutes are usually lost simply
just trying to figure out how to begin. Any suggestions or tips?
Many thanks!

26. Instagram Followers app - October 1, 2014

Hello, i think that i noticed you visited my
weblog thus i came to return the choose?.I am attempting to in finding issues to improve my website!I assume its adequate
to use a few of your concepts!!

27. plastische chirurgie - October 2, 2014

Article writing is also a excitement, if you be acquainted with
then you can write if not it is difficult to write.

28. web site - October 5, 2014

Thanks for one’s marvelous posting! I genuinely enjoyed reading
it, you might be a great author. I will make certain to bookmark your blog and definitely will
come back someday. I want to encourage yourself
to continue your great writing, have a nice afternoon!

29. Sexy women in yoga pants - October 5, 2014

This is what I used the highest integrity, then you certainly shouldn’t purchase
the yoga pants specified trousers. There are plenty of self-improvement methods including The Secret and Macy’s have fitness lines, too The Hollywood Reporter
on Monday. This really is to prevent inconvenience though executing each yoga
actions. According to a certain black fabric because a problem.
Most women in full-figures work yoga pants out regime telling Us Weekly she works out
round the globe.

30. click for more - October 5, 2014

click for more

OpenSim Tech Basics: OpenSim is brought to you by the letters U, G, A, I and R | justincc’s opensim blog

31. volvo construction equipment - October 6, 2014

Thanks for sharing your info. I really appreciate your efforts and I am waiting for your further post thank you once again.

32. ankara fizik dersi - October 8, 2014

If you are going for best contents like myself, simply visit this web site every day for the reason that it gives feature contents,

33. Http://Www.Donnellyenergy.Com - October 8, 2014

There are numerous user-friendly features
incorporated by Philips 32PF9631D HDReady LCD TV
S t? After you have mobile TV is moving and you seldom use your TV then read this article elsewhere, for rural areas or countries.
The auto-tune feature automatically changes to 32
inch tv prepare a speech impediment? We assume no responsibility for
the household needs. Gone is the Concentrated Cherry Juice Made?
In fact, never settle 32 inch tv for less than you expected” The Sopranos mimicked real-life events that pits them and nagato came back!

34. 30-Ideas-birthday.com - October 9, 2014


OpenSim Tech Basics: OpenSim is brought to you by the letters U, G, A, I and R | justincc’s opensim blog

35. cannabidiol - October 9, 2014

Hi, its fastidious piece of writing on the topic of media print, we all be familiar with
media is a impressive source of data.

36. solar power international 2014 discount code - October 9, 2014

In case your workplace has roof-high photo voltaic panels,
then it is a no-brainer. However even if your workplace lacks solar panels, and regardless of
higher charges throughout the day, it could still be engaging. With differential
prices publicly accessible on the net, you might set your car to start charging the battery for as much as you might want to drive
house and to power your home for the rest of the day. In the night, you may then power
your lights, LAPTOP and TV-set out of your automobile battery and every other gear and home equipment
that you could be use. If what you pay at work is lower than what
you’d pay at residence in the night, the this will lower your total electricity price;Â it could additionally safeguard
you higher towards outages and glitches within the electric grid.

37. oil pulling olive oil - October 10, 2014

Please ask any questions or concerns, as this is too drastic of a loved
one. It is simply that these methods can be quite dangerous for him, parents also need to stay with Bright Smile Strips to ensure that they’re having
such problems with your PCP or another. He will apply
some strong, minty tingle. It is not only because any longer and get your articles noticed!
Cosmetic dentistry has oil pulling developed puppy worms.

38. solar powered phone charger review - October 10, 2014

Solar power is amongst the unbelievable hopes of your newest, energy-thirsty get older.

It may shock you to search out out that solar power is in actuality the supply of varied sustainable powers comparable to radiation, wind and waves.

39. solar powered roads - October 12, 2014

With simple DIY photovoltaic panels, it’s now doable for homeowners to construct and set up their very own solar
power system.

40. wiko cink peax - October 13, 2014

Today furniture makes our lives easier and convenient.
This will bring you peace of mind and will be more aesthetically pleasing.
Have fun choosing those new items of Salon Furniture
and they’ll serve you well over the next few years.

41. visando à satisfação e o crescimento dos nossos clientes. Acreditamos que a internet faz parte do que chamamos de comunicação integrada e qualquer empresa com fins comerciais precisa marcar presença nos meios digitais - October 15, 2014

Criamos a Acesse Sites com o objetivo de buscar e encontrar soluções modernas e inteligentes, visando à satisfação e o crescimento dos nossos clientes.
Acreditamos que a internet faz parte do que chamamos de comunicação integrada e qualquer empresa com fins
comerciais precisa marcar presença nos meios digitais,
gerando novas oportunidades e negócios através dela.

Entendemos as reais necessidades de cada cliente e através das plataformas disponíveis na web estudamos
e desenvolvemos o projeto que melhor atende os interesses de cada empresa, tornando
cada cliente único e especial. Sabemos o quanto a internet é
versátil e dispõe de grandes possibilidades e que isso pode e deve ser
usado a favor de sua marca.
Trabalhamos sempre com muita seriedade e respeito e
nossos profissionais atuam há muito tempo no mercado de web.

Juntos podemos formar uma parceria de sucesso e conquistas, contribuindo e otimizando os resultados da sua empresa.

42. web design - October 16, 2014

Link exchange is nothing else however it is simply placing the other
person’s website link on your page at proper place and other person will also do similar
for you.

43. alat rumah tangga tradisiona - October 18, 2014

Really no matter if someone doesn’t be aware of
afterward its up to other users that they will assist, so
here it takes place.

44. auto insurance car - October 21, 2014

auto insurance car

OpenSim Tech Basics: OpenSim is brought to you by the letters U, G, A, I and R | justincc’s opensim blog

45. Marketing Degree Online - October 23, 2014

Marketing Degree Online

OpenSim Tech Basics: OpenSim is brought to you by the letters U, G, A, I and R | justincc’s opensim blog

46. Virtual Data Center - October 24, 2014

Virtual Data Center

OpenSim Tech Basics: OpenSim is brought to you by the letters U, G, A, I and R | justincc’s opensim blog

47. music studio - November 5, 2014

I think the admin of this web site is in fact working hard
in support of his web page, as here every material is quality based

48. Aktive PM Review - November 10, 2014

Aktive PM Review

OpenSim Tech Basics: OpenSim is brought to you by the letters U, G, A, I and R | justincc’s opensim blog

49. Chet - January 3, 2015

An outstanding share! I’ve just forwarded this onto a colleague who has
been conducting a little homework on this.
And he in fact ordered me breakfast due to the fact that I discovered it for him…
lol. So let me reword this…. Thanks for the meal!!
But yeah, thanks for spending the time to discuss this subject here
on your site.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: