[omniORB] How can I creat a hot-standby name service?

[zlr]

Hi:
    Would you pls give the code of "process manager" and the neat C++
template which would wrapper an object reference and a instruction or guide
for the mentioned items?

Best Regards
ZHANG Liren
----------------------------------------------------------------------------

Singapore Technologies Electronics Ltd.
Product Development & Management Division (PDMD)
(65) 413 1613 (Direct)
zhanglr@stee.com.sg

----- Original Message -----
From: "Bruce Fountain" <fountainb@switch.aust.com>
To: <omniorb-list@realvnc.com>
Sent: Tuesday, July 23, 2002 11:04 AM
Subject: Re:Re: [omniORB] How can I creat a hot-standby name service?


> On Tuesday 23 July 2002 10:20, zlr wrote:
> >     I have tried to set the same OMNINAMES_LOGDIR path in two pcs where
I
> > have installed NameService. But I found, when NameService started, it
will
> > create two files (one is *.log, another is *.bak). They is both include
the
> > PC name in their file name. ( E.g. I have tow PC--PC1 as master and PC2
as
> > slave in hot-standby. it will create four files --omninames-PC1.log,
> > omninames-PC1.bak and omninames-PC2.log, omninames-PC2.bak).
> >
> >     And I also try to synchronization these files. I rename the
> > omninames-PC1.log to omninames-PC2.log and omninames-PC1. bak to
> > omninames-PC2.bak. But I found the NameService cannot be started in PC2.
>
> Server side - you might find it easier to modify your server to be aware
> of the redundant NS and register twice. On the hot standby system
> I developed most of the server processes were located on the same host as
> the NS, so on failover they would re-register anyway. For those server
> processes which were located on other hosts we had a "process manager"
> which would notify server processes in the event of failover. The server
> processes would then re-register with the new NS.
>
> >     As you say: In omniORB 3.0, there's no option but to make the
> > applications aware of the situation and have them retry if they get
> > COMM_FAILUREs.
>
> I wrote a neat C++ template which would wrapper an object reference. On
> construction you would give the ref a name, which was stored as a member
> variable. When a request was made the templatised object would check to
> see if it had a valid reference to the remote object. If not, it would
resolve
> it using the current NS. If an exception was thrown the reference would be
> cleared and re-resolved from scratch on the next invocation. The key was
> using lazy evaluation - the object would only attempt to resolve the name
> on demand, rather than all objects attempting to resolve simultaneously.
> This worked well with omniORB 3.0.3, although the omniORB 4.0 multiple
> ref syntax would obviously be simpler.
>
> >     But if I register the servers to another NameService (PC2) after
> > swiching over. Do I have to restart all servers (Messaging Server,
Routing
> > Server ...)?
>
> Not entirely sure what your architecture is here, but our approach was
> to run a "process manager" process on each host. Whenever a CORBA
> process was launched on that host it would register with the PM. The
> PM's job was to keep track of things like failover and notify each of the
> registered processes when something changed. The processes could
> then re-register with the NS or re-resolve references to other servers.
>
> The PM also looked after restarting failed processes etc. and providing
> bootstrap parameters to registering processes.
>
> The PM itself is a single point of failure, so it is important to keep it
> as simple and robust as possible.
>
> --
> Bruce Fountain (fountainb@switch.aust.com)
> Senior Software Engineer
> Union Switch and Signal Pty Ltd
> Perth Western Australia
> tel: +618 9256 0083
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>
>