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> Think of it like a procedure call between machines. :-)
Normally prorams can't call functions in other programs. (Unless you
count the operatin system.) And certainly not in programs runnin on
another machine.
I guess that's what this technology brings to the table. (Whatever the
technology is actually called...)
OOC, is there some better way rather than tunnelling over HTTP? Surely
somebody has already come up with sane designs for this?
>> What's REST then?
>
> Representational State Transfer. A set of rules that almost nobody who
> claims to use REST actually follows.
Sounds delightful.
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Orchid XP v8 <voi### [at] dev null> wrote:
> > Think of it like a procedure call between machines. :-)
> Normally prorams can't call functions in other programs. (Unless you
> count the operatin system.) And certainly not in programs runnin on
> another machine.
In many object-oriented languages, such as for example objective-C,
dynamic binding is done with a messaging system. In other words, when
you want to call the member function of an object (even if you don't
know the exact type of that object, but only have an abstract handle
to it), what happens internally is that a "message" is sent at runtime
to that object, and the object can accept it (in practice by the object's
type implementing the proper member function) or not. In practice this is
very much like a member function call (except that you don't necessarily
need to know that the object supports that function call).
It's perfectly possible to send these messages between procedures, and
I assume even if these procedures are running in different computers. So
basically it ends up being one program calling the member function of an
object in another program (possibly running on a different computer).
Here's some documentation about remote messaging in objective-C:
http://tinyurl.com/9339sk
--
- Warp
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Orchid XP v8 wrote:
> I guess that's what this technology brings to the table. (Whatever the
> technology is actually called...)
Exactly. The general term is "remote procedure call", or "RPC".
> OOC, is there some better way rather than tunnelling over HTTP? Surely
> somebody has already come up with sane designs for this?
Yes, and yes. And, to answer your next question, yes.
>>> What's REST then?
>>
>> Representational State Transfer. A set of rules that almost nobody
>> who claims to use REST actually follows.
>
> Sounds delightful.
To be a little less obtuse, it's a few guiding principles that make it
possible to cache stuff and supposedly figure out interfaces on your own.
Such principles include using a URL to identify every resource, and to have
the body of resources include URLs to refer to other URLs; but the REST
moniker requires much more to work "properly", including (for example)
storing no "state" at the server. In other words, HTML over HTTP, "done
right" in some important senses, so that you can cache the results properly
and etc.
People then take anything that encapsulates the request over HTTP in a way
that assigns different URLs to resources to be "REST". That's a tiny and
fairly useless part of it.
SOAP can't be "REST" because the URL identifies only the server and the
function name and arguments go in the body of the request.
--
Darren New, San Diego CA, USA (PST)
Why is there a chainsaw in DOOM?
There aren't any trees on Mars.
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>> And I'm also wondering just how much all this stuff actually *costs*...
>
> CPU hours are a bit expensive, but comparable to renting a shared server
> somewhere else (except you get a "dedicated" server). The rest is really
> cheap. Hit aws.amazon.com for details.
Well now... It seems that even if you store some absurd amount of data
like 1GB (think how many years that would take to upload...) it costs
less than 50p/month. Which is nothing. (I currently pay £5/month.)
On the other hand, 30 days of instance time on EC2 is almost 80$.
Exchange rates vary, but this compares wildly unfavourably with my
current hosts' demands of £15/month.
The verdict: S3 is very, very cheap. EC2 is absurdly expensive. (If
you're a company, the reliability guarantees and lack of initial outlay
could make sense. But for an individual, it's a no-brainer: don't do it!)
For about £200 you could *buy* a half-decent PC. If you leave it running
for 1 year, it will have cost you [slightly more than] £200. If you run
EC2 for 1 year, it will cost 964.15$, which I would suggest is slightly
more than £200, whatever the exchange rate is.
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Invisible wrote:
> Well now... It seems that even if you store some absurd amount of data
> like 1GB (think how many years that would take to upload...) it costs
> less than 50p/month. Which is nothing. (I currently pay £5/month.)
Yep. I think my last bill was seventeen cents.
> On the other hand, 30 days of instance time on EC2 is almost 80$.
> Exchange rates vary, but this compares wildly unfavourably with my
> current hosts' demands of £15/month.
Is that for a machine where you can install your own OS and such? Or is t
hat
for just a web host, where you're (for example) sharing an Apache server
with others?
> The verdict: S3 is very, very cheap. EC2 is absurdly expensive. (If
> you're a company, the reliability guarantees and lack of initial outlay
> could make sense. But for an individual, it's a no-brainer: don't do it
!)
It's also designed for you to rent it briefly, not for a long time. I.e.,
if
your needs aren't "elastic", it might not make sense. If you need six
machines today, three tomorrow, and one next week, it makes more sense. I
f
you want to rent a machine for three hours to do a render, it makes a lot
of
sense.
> For about £200 you could *buy* a half-decent PC. If you leave it r
unning
> for 1 year, it will have cost you [slightly more than] £200.
Well, you would need the connectivity too, which I understand is pretty
expensive where you are. :-)
--
Darren New, San Diego CA, USA (PST)
Why is there a chainsaw in DOOM?
There aren't any trees on Mars.
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>> Well now... It seems that even if you store some absurd amount of data
>> like 1GB (think how many years that would take to upload...) it costs
>> less than 50p/month. Which is nothing. (I currently pay £5/month.)
>
> Yep. I think my last bill was seventeen cents.
To quote the bitch from Friends, "ooo, that's *interesting*!"
>> On the other hand, 30 days of instance time on EC2 is almost 80$.
>> Exchange rates vary, but this compares wildly unfavourably with my
>> current hosts' demands of £15/month.
>
> Is that for a machine where you can install your own OS and such? Or is
> that for just a web host, where you're (for example) sharing an Apache
> server with others?
That's for root SSH access to a Linux box that you can install whatever
you want on. (Although presumably you can't change the OS - how would
you talk to it while you're installing it?) Several flavours of Linux
availbable.
It is a *virtual* server though - your stuff runs in a virtualisation
system. (They claim to guarantee a certain minimum performance level
though.)
If you want a *dedicated* server (i.e., a real physical box that's just
for you) it's drastically more expensive - like £90/month or something.
>> The verdict: EC2 is absurdly expensive.
>
> It's also designed for you to rent it briefly, not for a long time.
As with any kind of renting, there will always be a point where renting
becomes more expensive than buying. The question is only where that
point is.
If you just want to *run* stuff, EC2 sets the tipping point really,
really low. (E.g., the POV-Ray thing I'm currently trying to do will
probably take at least a week, more likely a month. And I want to do a
whole series of others afterwards. For the price EC2 want, I could
probably buy a killer PC several times over.)
The advantace of EC2 is either
- You only want it for a little while.
- You want to do something that requires massive amounts of Internet
bandwidth.
Buying a PC which out-performs EC2 in compute terms only isn't
expensive. Beating the connectivity EC2 is likely to have would be...
uh... "expensive".
> If you want to rent a machine for three hours to do a
> render, it makes a lot of sense.
It does? Surely it would make more sense to just run it on my own PC for
3 hours, while I go watch TV or something. Costs £0. :-P
>> For about £200 you could *buy* a half-decent PC. If you leave it
>> running for 1 year, it will have cost you [slightly more than] £200.
>
> Well, you would need the connectivity too, which I understand is pretty
> expensive where you are. :-)
Maybe that's it: Rendering stuff doesn't require gigabit Internet access!
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Orchid XP v8 wrote:
> That's for root SSH access to a Linux box that you can install whatever
> you want on. (Although presumably you can't change the OS - how would
> you talk to it while you're installing it?) Several flavours of Linux
> availbable.
Impressive. (Cost-wise, I mean.) I guess this is one of the great wins
of
virtualization.
> It is a *virtual* server though - your stuff runs in a virtualisation
> system. (They claim to guarantee a certain minimum performance level
> though.)
Same with Amazon, I expect. They talk about it as "equivalent to a ...."
so
I assume it's a shared image thingie. Especially since you boot it by
giving it an image split into a bunch of parts on S3, so there's got to b
e a
pretty sophisticated boot loader going on there already.
> As with any kind of renting, there will always be a point where renting
> becomes more expensive than buying. The question is only where that
> point is.
Agreed. It's also designed for you to (for example) spin up more servers
for
your shopping carts during the christmas rush.
> If you just want to *run* stuff, EC2 sets the tipping point really,
> really low. (E.g., the POV-Ray thing I'm currently trying to do will
> probably take at least a week, more likely a month. And I want to do a
> whole series of others afterwards. For the price EC2 want, I could
> probably buy a killer PC several times over.)
Sure. I'm not trying to defend ECC's pricing, mind. :-)
> Buying a PC which out-performs EC2 in compute terms only isn't
> expensive. Beating the connectivity EC2 is likely to have would be...
> uh... "expensive".
You pay for the bandwidth, too. Not a lot, but again you have to measure
how
much you need and what it'll cost.
>> If you want to rent a machine for three hours to do a render, it makes
>> a lot of sense.
>
> It does? Surely it would make more sense to just run it on my own PC fo
r
> 3 hours, while I go watch TV or something. Costs £0. :-P
Assuming you didn't have one you could render on, of course.
--
Darren New, San Diego CA, USA (PST)
Why is there a chainsaw in DOOM?
There aren't any trees on Mars.
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>> That's for root SSH access to a Linux box that you can install
>> whatever you want on. (Although presumably you can't change the OS -
>> how would you talk to it while you're installing it?) Several flavours
>> of Linux availbable.
>
> Impressive. (Cost-wise, I mean.) I guess this is one of the great wins
> of virtualization.
Indeed yes.
>> It is a *virtual* server though - your stuff runs in a virtualisation
>> system. (They claim to guarantee a certain minimum performance level
>> though.)
>
> Same with Amazon, I expect.
Yeah. Although the fact that it takes a minute or two to start up makes
me think it's spending time trying to find a free machine to run it on.
Maybe each physical machine runs up to X virtual machines or something?
(I would imagine transfering a runnin image from place to place would be
infeasieble, even in a datacenter.)
>> As with any kind of renting, there will always be a point where
>> renting becomes more expensive than buying. The question is only where
>> that point is.
>
> Agreed. It's also designed for you to (for example) spin up more servers
> for your shopping carts during the christmas rush.
Indeed. If you're a company and you're large enough to actually need
*more than one* server at short notice, EC2 totally makes sense. For an
individual user who just wants some POV-Ray time... EC2 does not, even
remotely, make sense.
>> Buying a PC which out-performs EC2 in compute terms only isn't
>> expensive. Beating the connectivity EC2 is likely to have would be...
>> uh... "expensive".
>
> You pay for the bandwidth, too. Not a lot, but again you have to measure
> how much you need and what it'll cost.
You can easily buy a machine, put it in your kitchen, and leave it
running all day. But you can't easily get seriously low latency to the
Internet. EC2 gives you that. ;-)
>>> If you want to rent a machine for three hours to do a render, it
>>> makes a lot of sense.
>>
>> It does? Surely it would make more sense to just run it on my own PC
>> for 3 hours, while I go watch TV or something. Costs £0. :-P
>
> Assuming you didn't have one you could render on, of course.
Well, you need to own a PC in order to design it in the first place. ;-)
Plus, as I say, buying a PC works out vastly cheaper than using EC2 if
all you want is computer time.
Now, how does GPGPU change this picture? ;-)
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Orchid XP v8 wrote:
> Yeah. Although the fact that it takes a minute or two to start up makes
> me think it's spending time trying to find a free machine to run it on.
It might be that, altho I'd expect it's more a matter of transferring the
multi-gigabyte OS from S3, decompressing and decrypting it, putting it on
the disk as a virtual drive, and then booting it up.
> Maybe each physical machine runs up to X virtual machines or something?
That would be my guess, especially since they guarantee a certain amount of
performance, and they let you pick how many CPUs you'll have, and so on. :-)
> (I would imagine transfering a runnin image from place to place would be
> infeasieble, even in a datacenter.)
Shouldn't be *too* hard, if all you're talking about is moving the disk
image. It's not like you get to hook up special devices or anything. It
would lose all the TCP connections, most likely.
> individual user who just wants some POV-Ray time... EC2 does not, even
> remotely, make sense.
Unless you want to spin up 20 machines for one hour to do a trace, say. :-)
Or if you don't have access to the sort of thing you're talking about.
> Well, you need to own a PC in order to design it in the first place. ;-)
True. Depends of course on how studly your machine is. You started this by
complaining you couldn't let the render run overnight, didn't you? :-)
--
Darren New, San Diego CA, USA (PST)
Why is there a chainsaw in DOOM?
There aren't any trees on Mars.
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On Wed, 14 Jan 2009 22:11:27 +0000, Orchid XP v8 wrote:
> Yeah. Although the fact that it takes a minute or two to start up makes
> me think it's spending time trying to find a free machine to run it on.
> Maybe each physical machine runs up to X virtual machines or something?
There are systems out there that allow dynamic reallocation of physical
resources for virtual systems, so for example if you have 5 VMs running
on a single physical box and the performance spikes on one of the VMs,
the others can be dynamically moved to another physical system even while
running.
Some of the features of large-scale virtualization farms are quite
impressive these days in being able to do that. "Workload management" is
the term I hear our marketing folks (yeah, Novell has marketing folks!)
use.
The server farm that we use for our practical exams currently doesn't do
that, but I'm talking with the implementation team about how we could
dynamically scale if we needed to, and there's a solution available from
a company we bought in 2008 (which of course should make it incredibly
cheap for us to use internally).
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