Re: shared memory problem on network

Hi Bill/bryan et al.

I was planning to load-test my daemon service
"lockerd" which is running as the lock-server on
my
network.

I cant seem to find a starting-point on how to achieve
this. Any pointers would really help.

Best regards,
Ukh




--- ukhas jean <ukh_dtlyahoo.com> wrote:

> Hi Bill/bryan et al.
>    
>   I am running"lockerd" and have written a
client
> script which uses IPC::Locker.
>   The client is able to "switch" servers (in
case
> any one server is down using the same module.
>    
>   Thanks guys !
>    
>   --Ukh 
> 
> Bill Luebkert <dbecollroadrunner.com> wrote:
>   Brian Raven wrote:
> > 
> >>Hi Bill/Bryan et al.,
> >> 
> >>I was trying to implement the reader-writers
> locking mechanism using
> > 
> > shared memory. I am using IPC::Shareable 
> > 
> >>to implement this.
> >>The apache-instances are currently running on
only
> an individual
> > 
> > server (say A1) and all are able to access 
> > 
> >>this shared memory; and things work just fine.

> >> 
> >>But on "live/production" environment,
there are
> 4-5 servers (say, the
> > 
> > others are A2, A3, A4 and A5 
> > 
> >>respectively); each running several instances
of
> Apache-mod-perl.
> >>
> >>Right now the shared memory is only on A1. 
> >>So if A1 goes down (due to any reason), all my
> other applications
> > 
> > would be starved as the shared memory was 
> > 
> >>implemented on A1 and all instances across all
the
> servers were
> > 
> > accessing this shared memory.
> > 
> >> 
> >>Is there any way I can have a shared memory
> mutually accessible to all
> > 
> > the servers?
> > 
> >>So that in case A1 goes down, some other
server
> can take take control
> > 
> > of the shared memory.
> > 
> >>Any pointers would be much appreciated.
> > 
> > 
> > AFAIK, shared memory only works for processes on
> the same server.
> 
> In the historical definition, that would make sense.
> You could, I suppose,
> think of sharing memory across a network though if
> you stretched the def
> a bit. Of course, that really complicates the
> locking process although
> I believe there are *NIXs that have network locking
> implemented (haven't
> played in that arena much lately).
> 
> >>From your description, what you actually want
is a
> distributed locking
> > mechanism. Shared memory, i.e. how you wanted to
> implement it, is
> > actually a red herring. If you were to search
CPAN
> for something like
> > "distributed lock" you might see a
couple of
> modules that might help
> > such as IPC::Lock and IPC::Locker. Note that they
> don't seem to work on
> > all platforms.
> 
> If you can't find something appropriate that works
> on whatever platforms
> you have, you could consider making a TCP lock
> server or data server.
> 
> What are you trying to lock (I assume some sort of
> data file that is
> being written and read at the same time) ? and is
> that data available
> (or could it be made available) on any of the
> servers ?
> 
> If you serialize the requests through a single
> read/write TCP server,
> you shouldn't need to worry about locks (assuming
> that one server could
> handle all the traffic).
> 
> You could make the server movable too if one server
> went down, you could
> vote in a new one to take over and periodically
> update all the servers
> with the historical data so they wouldn't lose much
> on a takeover.
> 
> Give us a bit more info of what you're
> sharing/locking and what platforms
> you have to deal with.
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