From: Christopher Aldridge <caldridge@...>
Date: 2005-08-10T08:59:00+09:00
Subject: Re: drb server using file/tail to read file, and update client?

Thank you for your response..

This was exactly what I did before asking and I feel like it's hacky..
Do you have an example of the latter instead of the former?  Perhaps
something with tuplespace/rinda?

Here's the code I've been using in case anyone can use it:

<client defs>
	def Execute(global, system)
		Thread.new do
			begin
				DRb.start_service global['clientConnectionString'], EbdnxClient.new					
				DRb.thread.join
			rescue DRb::DRbBadURI
				puts "rescued"
				Vars.new.session(global)
				begin
					DRb.start_service global['clientConnectionString'], EbdnxClient.new			
					DRb.thread.join
				rescue DRb::DRbBadURI
					puts "Couldnt bind for monitoring. Exiting."
					exit 0
				end
			end
		end
		sleep 2
		begin
			DRbObject.new(nil, system['connectionString']).Execute(global, system)
			puts "client> server received job. pending status.."
		rescue
			puts "Could not connect to #{system['connectionString']}\ntrying
again in 2 seconds..."
			sleep2
			begin
				DRbObject.new(nil, system['connectionString']).Execute(global, system)
			rescue
				puts "Unable to connect to server #{system['connectionString']}"
				exit 0
			end
		end
		if system['authFailure'] == "true"
			puts "Authentication Failure"
			exit 1
		end
		DRbObject.new(nil, system['connectionString']).Monitor(global,
system) if global['output'] != "quiet"
	end

</client defs>
<server defs>
def Monitor(global, system)
		begin
			ebdnxLogStructure = "whatever.txt"
			if File.exists?("B:/LOGS/" + ebdnxLogStructure) == false
				sleep 7
				if File.exists?("B:/LOGS/" + ebdnxLogStructure) == false
					puts "log file still not found. sleeping 5 and forcing continue."
					sleep 5
				else
					puts "log file found"
				end
			end
			File::Tail::Logfile.open("B:/LOGS/" + ebdnxLogStructure, :rewind =>
5) do |log|
			    log.tail { |line| 
					if /<\/ebdnx>/.match(line)
						begin
							StatusToClient.new.Update(line, global)
						rescue DRb::DRbConnError
							puts "server> completed."
							break
						end
					else
						StatusToClient.new.Update(line, global)
					end
				}
			end
		rescue
			puts "server> unable to tail log: B:/LOGS/" + ebdnxLogStructure
		end
end
</server defs>


Obviously these are implemented in classes but Id like to see a way of
updating the client without having start a new drb service(on the
client).

Is this possible?  Thank you!!

On 8/9/05, Ryan Leavengood <mrcode@netrox.net> 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.
> 
> Here is an example of the former:
> 
> Server:
> 
> require 'drb/drb'
> 
> class TailServer
>   def initialize
>     @clients = []
>   end
> 
>   def register(uri)
>     puts "Client registered at: #{uri}"
>     @clients << DRbObject.new(nil, uri)
>   end
> 
>   def sendline(line)
>     puts "Sending line: #{line}"
>     @clients.each do |c|
>       c.addline(line)
>     end
>   end
> end
> 
> ts = TailServer.new
> DRb.start_service('druby://localhost:3456', ts)
> 
> # Obviously the code below needs to be replaced with code
> # that actually tails the log file
> i = 0
> loop do
>   sleep(5)
>   ts.sendline("This is line #{i}.")
>   i+=1
> end
> DRb.thread.join
> 
> Client:
> 
> require 'drb/drb'
> 
> class TailClient
>   def addline(line)
>     puts line
>   end
> end
> 
> # nil in the first parameter opens a random port
> DRb.start_service(nil, TailClient.new)
> server = DRbObject.new(nil, 'druby://localhost:3456')
> server.register(DRb.uri)
> DRb.thread.join
> __END__
> 
> Ryan
> 
>