orbitcpp-list

[orbitcpp-list] perform_work, pending_work, can't work when blocking

[<la...@se...>]

Perhaps I'm writing software all wrong, but I'm surprised how many
challenges I'm running into using orbit for a simple but real server.
I'm doubly surprised because I see so many postings of people working
on the software.  Perhaps the problems I'm having are really odd.

I'd like the server to do something useful in addition to handling
client requests (re-registering itself with a list of servers in a timely
manner, like every few minutes).  I can imagine many scenarios
where it is not acceptable to have orb->run() essentially lockup your
server now and forevermore!

I see someone has at least thought about this by the tantilizing but
unimplemented pending_work and perform_work methods in
orbitcpp_orb.hh.

Does anyone else have the need for this?  Is anyone working on it?
I've  hacked a version that sets an alarm in src/IIOP/connection.c
before select is called, then perform my work in the signal handler.
This is inferior to a real implementation.  If anyone is working on a
real implementation, please let me know so I can help and use it.  If
no one is working on this, also let me know and perhaps I will then
write the real implementation.

Also, in a previous email, I pointed out the problem in orbit where
a client will hang indefintely when the server crashes.  Can it be
no one else has a problem with this behavior?!  I fixed this by hacking
orbit's src/orbit-idl-compiler/backends/corbit-idl-c-stubs.c where it
generated "write" code that did not error check because the environment
variable BACKWARDS_COMPAT_0_4 was defined.

-Lance.

--
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Lance Welsh              la...@se...
Seascape Communications  (650) 327-6890
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[orbitcpp-list] Re: perform_work, pending_work, can't work when blocking

[Sam C. <sa...@to...>]

la...@se... <la...@se...> wrote:
>=20
> I see someone has at least thought about this by the tantilizing but
> unimplemented pending_work and perform_work methods in
> orbitcpp_orb.hh.
>=20
> Does anyone else have the need for this?  Is anyone working on it?
> I've  hacked a version that sets an alarm in src/IIOP/connection.c
> before select is called, then perform my work in the signal handler.
> This is inferior to a real implementation.  If anyone is working on a
> real implementation, please let me know so I can help and use it.  If
> no one is working on this, also let me know and perhaps I will then
> write the real implementation.

I have need for this, to implement a sort of timeout on various objects, for
protection from clients that misbehave. Luckily I don't need it right now,
but I will soon.

If all you're trying to do is avoid blocking (synchronous) operations, then
you can use DII or a multithreaded ORB for the server.

If you want a timeout event, then the best way is probably for the ORB to u=
se
the glib event loop instead of calling select() directly.

There have been murmurs about the next version of ORBit using the glib event
loop, which would make it possible to register your own timeout events. I
don't know if that's still part of the plan. Multithreading support was also
mentioned a few times, but again, I don't know if that's still part of the
plan either. Would any ORBit developers (Elliot?) like to comment?

You can find a multithreaded ORB (ORBit-mt) at:

http://goethe.ira.uka.de/~wilhelmi/corba/orbit-mt.html

I'm fairly sure that ORBit-mt uses the glib event loop, meaning you should
be able to register your own timeout events instead of using a signal
handler.
--=20
Sam Couter          |   Internet Engineer   |   http://www.topic.com.au/
sa...@to...    |   tSA Consulting      |
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Re: [orbitcpp-list] Re: perform_work, pending_work, can't work when blocking

[Brian M. <ba...@sn...>]

>>>>> "Sam" == Sam Couter <sa...@to...> writes:

    Sam> If you want a timeout event, then the best way is probably
    Sam> for the ORB to use the glib event loop instead of calling
    Sam> select() directly.

    Sam> There have been murmurs about the next version of ORBit using
    Sam> the glib event loop, which would make it possible to register
    Sam> your own timeout events. I don't know if that's still part of
    Sam> the plan. Multithreading support was also mentioned a few
    Sam> times, but again, I don't know if that's still part of the
    Sam> plan either. Would any ORBit developers (Elliot?) like to
    Sam> comment?

From <URL:http://icps.u-strasbg.fr/~genaud/ORBIT/x421.htm>

"Unfortunately, I don't really see how to do timeouts with the normal
CORBA event model, so I'm going to have to use the ORBit-specific hack
of having a glib event loop which supports both CORBA events and
timeouts. Another way, I am told, is something called an Evictor
pattern. I should understand this soon once I get my fancy CORBA book
in the mail.  The final way is just to leak memory like a sieve leaks
goldfish; this is the easiest thing to do."

1. What is the glib even loop? Is it or isn't it supported by ORBit?
2. What is the evictor pattern?

Of course, this document seems to be really old now (looks the same
last time I looked at it, 1 year+ ago), so not sure if it still
applies.
-- 
Brian May <ba...@sn...>

Re: [orbitcpp-list] Re: perform_work, pending_work, can't work when blocking

[Michael R. <mi...@ru...>]

----- Original Message -----
From: "Brian May" <ba...@sn...>
To: <orb...@li...>
Sent: Donnerstag, 21. Dezember 2000 09:08
Subject: Re: [orbitcpp-list] Re: perform_work, pending_work, can't work when
blocking


> >>>>> "Sam" == Sam Couter <sa...@to...> writes:
>
>     Sam> If you want a timeout event, then the best way is probably
>     Sam> for the ORB to use the glib event loop instead of calling
>     Sam> select() directly.
>
>     Sam> There have been murmurs about the next version of ORBit using
>     Sam> the glib event loop, which would make it possible to register
>     Sam> your own timeout events. I don't know if that's still part of
>     Sam> the plan. Multithreading support was also mentioned a few
>     Sam> times, but again, I don't know if that's still part of the
>     Sam> plan either. Would any ORBit developers (Elliot?) like to
>     Sam> comment?
>
> From <URL:http://icps.u-strasbg.fr/~genaud/ORBIT/x421.htm>
>
> "Unfortunately, I don't really see how to do timeouts with the normal
> CORBA event model, so I'm going to have to use the ORBit-specific hack
> of having a glib event loop which supports both CORBA events and
> timeouts. Another way, I am told, is something called an Evictor
> pattern. I should understand this soon once I get my fancy CORBA book
> in the mail.  The final way is just to leak memory like a sieve leaks
> goldfish; this is the easiest thing to do."
>
> 1. What is the glib even loop? Is it or isn't it supported by ORBit?
> 2. What is the evictor pattern?

For the evictor question have a look at
http://industry.ebi.ac.uk/~lcwang/corba-wks/evictor/sld001.htm or for a more
detailed explanation read the LifeCycle Mgmt chapter in "Advanced CORBA
Programming with C++" (Michi Henning and Steve Vinoski)

Michael

Re: [orbitcpp-list] Re: perform_work, pending_work, can't work when blocking

[<MHL...@t-...>]

On Don, 21 Dez 2000 09:08:59 Brian May wrote:
> [...]
> 
> 1. What is the glib even loop? Is it or isn't it supported by ORBit?

"glib event loop" refers to a set of functions defined by the library
glib which can be invoced on a datastructure called GMainLoop.
This datastructure e.g. holds timeouts or file descriptors to poll.
If you want to use the glib event loop you
- allocate the data structure
- register timeouts and file descriptors
- call g_main_run or repeatadly call g_main_iteration.
(See glib/gmain.h)

ORBit currenctly doesn't register its file descriptors for the glib event
loop but uses its own algorithms. ORBit-mt _does_ use the event loop so
it is no problem to register your own timeouts etc. which then coexist
with ORBit's file descriptors.
If you look in CVS for the ORBit2 sources you can see that once finished,
ORBit2 will most likely use the glib event loop.


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