From: Alexander Lamb <Alexander.J.Lamb@...>
Date: 2005-10-21T20:55:43+09:00
Subject: Threads, timing and HTTP

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Hello list,

I am implementing a very simple script to ping web servers or =20
services (to monitor how our environment is functionning).

Some production url's run on more than one host. Therefore, I start a =20=

thread for each separate url.

The function run in my threads is:

     def doPing(uri_string, probe)
       s =3D uri_string
       while true
         begin
           timeout(@seconds_before_timeout) do |timeout_length|
             start =3D Time.new
             begin
               open(s) do |result|
                 if result.status[0] !=3D "200"
                   probe.addToLogFile([s,'ERR',0,result.status[1]])
                 else
                   probe.addToLogFile([s,'OK',Time.new - start,''])
                 end
               end
             rescue Exception
               probe.addToLogFile([s,'ERR',0,$!])
             end
           end
         rescue Timeout::Error
           probe.addToLogFile([s,'ERR',0,'timeout'])
         end
         sleep(@seconds_between_ping)
       end
     end

However, this is a problem. Indeed, I want also to measure the time =20
(round-trip) it takes for the ping (these are only simple pings for =20
the time being). As you can see I get the local time before and after =20=

the call. But this doesn't work with threads. Indeed, since the =20
process is shared among threads, the time will be dependent on the =20
number of threads I am running and not a correct view of the actual =20
time it takes to ping.

I can't define the piece of code between the two times as critical =20
and only for one thread because if the open-uri blocks, it will =20
prevent another thread to ping another url in the mean time.

Any idea? Maybe use processes instead of threads?

Thanks for any hints!
--
Alexander Lamb
Service d'Informatique M=E9dicale
H=F4pitaux Universitaires de Gen=E8ve
Alexander.J.Lamb@sim.hcuge.ch
+41 22 372 88 62
+41 79 420 79 73






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