Requests hanging

If my Rails server has been sitting idle for a while, it does not
respond to
new requests.
What is the best way to troubleshoot something like that.

I am using Rails 3.0.7 in development.

On 9 May 2011 21:54, Alex K. [email protected] wrote:

If my Rails server has been sitting idle for a while, it does not respond to
new requests.
What is the best way to troubleshoot something like that.
I am using Rails 3.0.7 in development.

Is there anything in development.log when you submit the request (or
already there indicating a problem before the request)? What about in
the server terminal window?

Colin

I see nothing any where.

On Tue, May 10, 2011 at 9:25 AM, Alex K. [email protected]
wrote:

I see nothing any where.

To clarify, on your server terminal window, you see no output when you
try
to access a page? And of course the page does not load, I assume. It is
probably not this if you are seeing nothing at all on the terminal, but
sometimes if I forget to remove a debugger line and still am running the
server in --debugger mode then of course it hangs.

Otherwise, other obvious quations: have you restarted the server? As
well,
restarted your computer?

On 10 May 2011 15:45, Alex K. [email protected] wrote:

Please don’t top post, it makes it difficult to follow the thread.
Insert your replies at appropriate points in previous message. Thanks

I have restarted the server but not the computer. I am doing something
abnormal. Off of a request I start some external program as sub processes.
It takes about one second to start those sub processes. How long are we
allowed to delay the sending of a respond? Is there a better way do this in
Rails way? This problem is intermittent.

Where are you starting the sub processes? You said there was nothing
in the server or application development.log when you do the submit so
it is not getting as far as a rails action.

Colin

I have restarted the server but not the computer. I am doing something
abnormal. Off of a request I start some external program as sub
processes.
It takes about one second to start those sub processes. How long are we
allowed to delay the sending of a respond? Is there a better way do this
in
Rails way? This problem is intermittent.

On Tue, May 10, 2011 at 9:45 AM, Alex K. [email protected]
wrote:

I have restarted the server but not the computer. I am doing something
abnormal. Off of a request I start some external program as sub processes.
It takes about one second to start those sub processes.

Maybe you could post your code. One thing you might want to look at is
if
you can start it using another thread – especially if you have
something
which is apparently volatile. I call terminal commands all the time from
my
code, so itself should not be a problem. One way to do this could be
delayed_job but you can probably do it much more simply using a new
thread.
See: http://www.ruby-doc.org/core/classes/Thread.html

On Tue, May 10, 2011 at 9:56 AM, David K.
[email protected]wrote:

you can start it using another thread – especially if you have something
which is apparently volatile. I call terminal commands all the time from my
code, so itself should not be a problem. One way to do this could be
delayed_job but you can probably do it much more simply using a new thread.
See: http://www.ruby-doc.org/core/classes/Thread.html

this looks pretty good as an intro to threading, if it turns out that
this
is the correct route to go:
http://rubylearning.com/satishtalim/ruby_threads.html

I guess though if your process is important you will have to add some
handling in the case of failure if it were to happen.

On Tue, May 10, 2011 at 10:54 AM, Colin L. [email protected]
wrote:

On 10 May 2011 15:45, Alex K. [email protected] wrote:

Please don’t top post, it makes it difficult to follow the thread.

Sure!

Where are you starting the sub processes? You said there was nothing
in the server or application development.log when you do the submit so
it is not getting as far as a rails action.

I meant to say that I started the subprocesses in the previous request.
Here is my code:

class PortalMonitor
include Mongoid::Document
field :count, :type => Integer
field :url, :type => String
field :user, :type => String
field :password, :type => String
field :run, :type => Boolean

validates_presence_of :count, :url, :user, :password
validates_uniqueness_of :url

#embeds_many :emails
embeds_many :vidyo_desktops

after_create :desktop_start
before_destroy :desktop_stop
before_update :desktop_stop, :desktop_start, :if => :changed?

def desktop_stop
t1 = Time.now
Rails.logger.debug “######### Stop VidyoDesktops size =
#{vidyo_desktops.size} Dir = #{Dir.getwd} #########”
for vd in vidyo_desktops
Rails.logger.debug “######## #{vd.vd_pid} ######”
begin
Process.kill ‘TERM’, vd.vd_pid
rescue Errno::ESRCH
end
end
vidyo_desktops.delete_all
Rails.logger.debug “############# TIME SPENT STOP #{Time.now - t1}
##################”
end

def desktop_start
Rails.logger.debug “######### desktop_start ###########”
return if run == false
t1 = Time.now
count.times do |n|
n += 1
cmd = ‘lib/vidyo/VidyoDesktop’
eid = user + n.to_s
root = ‘lib/vidyo’
args = " --eid #{eid} --port #{51300+n} " +
“–video #{root}/ofer_wvga.vidyo --audio #{root}/ogm.wav”
cmd = cmd.to_s + args
pid, vd_stdin, vd_stdout, vd_stderr = Open4::popen4(cmd)
#eval("#{cmd}&")
#pid = $?.pid
=begin
Thread.new do
while (( line = vd_stderr.gets ))
puts “errrrrrrrrrr #{line}”
end
end
Thread.new do
while (( line = vd_stdout.gets ))
puts “ottttttttttt #{line}”
end
end
=end
Rails.logger.debug “######### Start VidyoDesktops #{pid} cmd =
#{cmd}
#########”
vidyo_desktops.create!(:vd_pid => pid, :pm_pid => 0, :pm_error =>
“Hello There!”)
Process.detach(pid)
#p vidyo_desktops
end
Rails.logger.debug “############# TIME SPENT START #{Time.now - t1}
##################”
end

end

On 10 May 2011 16:40, Alex K. [email protected] wrote:


I meant to say that I started the subprocesses in the previous request.

I suggest that you first disable the starting of the sub processes to
see whether the issues disappears.

Colin

On Tue, May 10, 2011 at 11:01 AM, David K.
[email protected]wrote:

It takes about one second to start those sub processes.

Maybe you could post your code. One thing you might want to look at is if
you can start it using another thread –

I avoided using Threads since I wanted my operations to be atomic.

On Tue, May 10, 2011 at 10:43 AM, Alex K. [email protected]
wrote:

On Tue, May 10, 2011 at 9:45 AM, Alex K. [email protected]wrote:

So what does the ‘desktop’ app or code do? It is it something that your
users depend on, and if so for what? What is the process? Of course
first do
what Colin asked and see if bypassing this process gets you back working
so
you at least know where to focus.

On 10 May 2011 17:40, Alex K. [email protected] wrote:
? …

I tried it with the subprocess and it does not hang.

Do you mean without?

Colin

On Tue, May 10, 2011 at 3:25 PM, Colin L. [email protected]
wrote:

On 10 May 2011 17:40, Alex K. [email protected] wrote:
? …

I tried it with the subprocess and it does not hang.

Do you mean without?

Sorry! Yes I meant without.

On Tue, May 10, 2011 at 12:04 PM, David K.
[email protected]wrote:

On Tue, May 10, 2011 at 9:56 AM, David K. [email protected]wrote:

Maybe you could post your code. One thing you might want to look at is
if you can start it using another thread –

I avoided using Threads since I wanted my operations to be atomic.

So what does the ‘desktop’ app or code do? It is it something that your
users depend on, and if so for what? What is the process? Of course first do
what Colin asked and see if bypassing this process gets you back working so
you at least know where to focus.

I tried it with the subprocess and it does not hang. Keep in mind that
hanging does not happen all the time.
The desktop app is a video conferencing desktop client on Linux. I think
I
would have to do Threads. I will let you know if it makes it better.

I think I have found a good solution for my background tasks.

http://kr.github.com/beanstalkd/

http://railscasts.com/episodes/243-beanstalkd-and-stalker

It’s exactly what I need, and it seems to be a simple and popular
solution.

On Wed, May 11, 2011 at 11:05 AM, David K.
[email protected]wrote:

It’s exactly what I need, and it seems to be a simple and popular
solution.

Thanks for sharing… I had not seen this and good to know about

Sure! And thanks to Railscasts new and improved website that lists
subject
categories .

On Wed, May 11, 2011 at 7:26 AM, Alex K. [email protected]
wrote:

I think I have found a good solution for my background tasks.

http://kr.github.com/beanstalkd/

http://railscasts.com/episodes/243-beanstalkd-and-stalker

It’s exactly what I need, and it seems to be a simple and popular solution.

Thanks for sharing… I had not seen this and good to know about

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