From: Christopher Aldridge <caldridge@...>
Date: 2005-08-15T08:01:21+09:00
Subject: Re: drb server using file/tail to read file, and update client?

Joel, FYI -- This worked GREAT!   :-)   Thank you!!!!!!!!!!

On 8/10/05, Christopher Aldridge <caldridge@gmail.com> wrote:
> Got it Joel.
> 
> I'll give it a try tomorrow morning.
> 
> Thanks again! :-)
> 
> On 8/9/05, Joel VanderWerf <vjoel@path.berkeley.edu> wrote:
> > Joel VanderWerf wrote:
> > > Ryan Leavengood wrote:
> > >
> > >>Christopher Aldridge said:
> > >>
> > >>
> > >>>Any suggestions or am I doing it the only way it can be done?
> > >>
> > >>
> > >>If I understand your problem correctly, the issue is that you now have to
> > >>constantly poll the server to see if there are more lines, when really
> > >>what you want is to have the server tell the clients of the new lines.
> > >>
> > >>So your options are either to code the clients so they also have a DRb
> > >>server, which the server connects to when outputting lines from the log
> > >>file, or possible to use Rinda and a Tuplespace.
> > >
> > >
> > > IIRC, the client can also call a method with a block. The block is
> > > undumped, so it remains on the client side, with a proxy on the server
> > > side. When the server's implementation of the method yields to the
> > > block, it calls the code on the client side. DRb is sooo elegant!
> > >
> > > An example of that idea is embedded in a little distributed chat server
> > > example that comes with my foxtails project, using distributed observers
> > > wired up to fox gui widgets. But it's probably easier to code this up
> > > from scratch, once you know that DRb supports distributed block yields.
> > >
> >
> > Here is an example of using callbacks by yielding from the server:
> >
> > ==== svr.rb ====
> > require 'drb'
> >
> > $callback = nil
> >
> > class C
> >   def foo
> >     3.times do |i|
> >       yield i
> >     end
> >   end
> >
> >   def bar(&pr)
> >     $callback = pr
> >   end
> > end
> >
> > obj = C.new
> >
> > DRb.start_service('druby://:22337', obj)
> >
> > begin
> >   loop do
> >     $callback.call if $callback
> >     sleep 1
> >   end
> > rescue DRb::DRbConnError
> >   puts "client is gone"
> > end
> > =========
> >
> > ==== clnt.rb ====
> > require 'drb'
> >
> > DRb.start_service()
> > obj = DRbObject.new_with_uri('druby://:22337')
> >
> > obj.foo do |i|
> >   p i
> > end
> >
> > obj.bar do
> >   puts "Got callback!"
> > end
> >
> > puts "press return to quit"
> > gets
> > ========
> >
> > output:
> >
> > 0
> > 1
> > 2
> > press return to quit
> > Got callback!
> > Got callback!
> > Got callback!
> > Got callback!
> >
> > --
> >       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
> >
> >
>