On Wed, Nov 18, 2009 at 10:23 AM, pharrington <xenogene...@gmail.com> wrote:
> On Nov 18, 12:32 pm, Conrad Taylor <conra...@gmail.com> wrote:
> > On Tue, Nov 17, 2009 at 1:07 PM, jhaagmans <jaap.haagm...@gmail.com>
> wrote:
> >
> > > Hi,
> >
> > > I have a backgroundrb worker that gets triggered every second. When
> > > it's triggered, it's supposed to make 2 - 15 http-requests using
> > > Net::HTTP. My idea was to put every execution into a thread so the
> > > next execution doesn't have to wait for the last one. So basically:
> >
> > > def http_requests
> > > hosts.each do |host|
> > > Thread.new do
> > > begin
> > > client = Net::HTTP.start(host)
> > > rescue
> > > #store host as inactive
> > > ensure
> > > client.finish if client.active?
> > > end
> > > end
> > > end
> > > end
> >
> > > Of course that's not all it does, but I hope you understand what I'm
> > > trying to do here.
> >
> > > The thing is: this doesn't get done once a second. It appears that
> > > every HTTP-request is waiting for the last one to complete, which
> > > clots up Rails very fast!
> >
> > > My question is: why is this? Does this have anything to do with Ruby
> > > not being threadsafe (I doubt it, because that just means threads
> > > aren't executed as precisely as with jRuby, right?) or is Net::HTTP
> > > not able to make requests while another Net::HTTP request is still
> > > running? And what to do?
> >
> > > I hope you can help.
> >
> > The Global Interpreter Lock (GIL) prevents threads from executing in
> > parallel when using Ruby 1.8.6 aka MRI, 1.8.7, and 1.9.1 aka YARV.
> > However, JRuby 1.3.x/1.4.x, MacRuby 0.5 Beta 2, Maglev and several
> > other upcoming Ruby VMs are not constrained by the GIL. Thus, they
> > can execute threads in parallel.
> >
> > Good luck,
> >
> > -Conrad
> >
>
> Emm just because the threads aren't all executing *simultaneously*
> doesn't that they aren't running in parallel (due to all the thread
> switching etc).
>
Each thread must acquire the lock before it can execute. Thus, it operates
similar to a queue data structure (i.e. first in first out (FIFO)) and this
is how
it work today in regards to Ruby 1.8.6, 1.8.7, and 1.9.1. I know the C
implementation
of the Ruby VM very well.
-Conrad
>
> Regardless, I can't seem to reproduce the OPs behviour:
>
> require 'net/http'
>
> def hosts
> %w[rubyforge.org www.scala-lang.org www.google.com www.gamefaqs.com
> allrecipes.com m2k2.taigaforum.com youtube.com gitorious.org
> everything2.com]
> end
>
> def http_requests
> hosts.each do |host|
> Thread.new do
> begin
> puts "fetching host #{host}"
> client = Net::HTTP.start(host)
> rescue e
> #store host as inactive
> ensure
> puts "finished with host #{host}"
> client.finish if client.active?
> end
> end
> end
> end
>
> irb(main):001:0> http_requests
> fetching host rubyforge.orgfetching host www.scala-lang.orgfetching
> host www.google.com
> fetching host www.gamefaqs.com
> fetching host allrecipes.com
> fetching host m2k2.taigaforum.com
> finished with host rubyforge.orgfetching host youtube.com
> fetching host gitorious.org
> finished with host www.google.com
> fetching host everything2.com
> => ["rubyforge.org", "www.scala-lang.org", "www.google.com",
> "www.gamefaqs.com", "allrecipes.com", "m2k2.taigaforum.com",
> "youtube.com", "gitorious.org", "everything2.com"]
> irb(main):002:0>
>
> finished with host www.scala-lang.org
> finished with host m2k2.taigaforum.comfinished with host www.gamefaqs.com
> finished with host allrecipes.com
>
>
> finished with host youtube.com
> finished with host everything2.com
> finished with host gitorious.org
>
> Am I missing something or misunderstanding the question?
>
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