Why so many worker threads?

Why so many worker threads?

[Alexey Chernenkov]

Hello!

Can anyone explain why my Unicorn installation (for RoR site) have so
many worker threads?

  * screenshot: http://i.stack.imgur.com/U9TFR.png
  * unicorn.rb: https://gist.github.com/907th/4995323

Thanks!
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Re: Why so many worker threads?

[Eric Wong]

Alexey Chernenkov <laise@pisem.net> wrote:
> Hello!
> 
> Can anyone explain why my Unicorn installation (for RoR site) have so
> many worker threads?
> 
>   * screenshot: http://i.stack.imgur.com/U9TFR.png
>   * unicorn.rb: https://gist.github.com/907th/4995323

It's probably some gem/library you're using which spawns threads behind
your back.  Ruby 1.9/2.0 only has one extra thread per-process for
accepting signals.
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Re: Why so many worker threads?

[Alejandro Riera]

>   * screenshot: http://i.stack.imgur.com/U9TFR.png

which command did you run to show that list?
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Re: Why so many worker threads?

[Alexey Chernenkov]

2013/3/1 Alejandro Riera <ariera@gmail.com>:
> which command do you run to show that list?
>
> On 1 March 2013 18:41, Eric Wong <normalperson@yhbt.net> wrote:
>>
>> Alexey Chernenkov <laise@pisem.net> wrote:
>> > Can anyone explain why my Unicorn installation (for RoR site) have so
>> > many worker threads?
>> >
>> >   * screenshot: http://i.stack.imgur.com/U9TFR.png
>> >   * unicorn.rb: https://gist.github.com/907th/4995323
>>
>> It's probably some gem/library you're using which spawns threads behind
>> your back.  Ruby 1.9/2.0 only has one extra thread per-process for
>> accepting signals.

Screenshot? Its `htop` command with tree (F5) view.
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Re: Why so many worker threads?

[Alexey Chernenkov]

2013/3/1 Eric Wong <normalperson@yhbt.net>:
> Alexey Chernenkov <laise@pisem.net> wrote:
>>
>> Can anyone explain why my Unicorn installation (for RoR site) have so
>> many worker threads?
>>   * screenshot: http://i.stack.imgur.com/U9TFR.png
>>   * unicorn.rb: https://gist.github.com/907th/4995323
>>
>
> It's probably some gem/library you're using which spawns threads behind
> your back.  Ruby 1.9/2.0 only has one extra thread per-process for
> accepting signals.
>

Could you advise me how I can determine which gem causes the problem?
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Re: Why so many worker threads?

[Alejandro Riera]

>>> >   * screenshot: http://i.stack.imgur.com/U9TFR.png
>>> >   * unicorn.rb: https://gist.github.com/907th/4995323
>> which command do you run to show that list?
>
> Screenshot? Its `htop` command with tree (F5) view.


I have just one worker. If I run top I just see one master and one
worker. But with htop there are 3 masters and 3 workers, each of them
with a different pid. This is a surprise to me too. I'm runnnig ruby
1.9.2.
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Re: Why so many worker threads?

[Tatsuya Ono]

NewRelic and Airbrake are popular gems which spawns threads.

Unfortunately I don't think there is a silver bullet to detect which
gems are doing that. You have to investigate it step by step. For
example, you can create a new Rails app with the Gemfile(assuming you
use bundler), config and initializers. If you succeeded to reproduce
the problem with the small app, the rest of research would not be
difficult. You remove a gem one by one and restart app and you may
want to make some requests, then check the number of threads. If the
number of threads is reduced, that's would be it.

Or maybe you can grep your gem library directory with some keywords
like "Thread" or "Proc"? If you install gem library to specific path
(--path option on Bundler) for the application, you can avoid look at
other gems installed by other ruby application.
http://gembundler.com/v1.2/bundle_install.html


I don't think that the problem is related to Unicorn though.

Good luck :-)

On 1 March 2013 19:14, Alejandro Riera <ariera@gmail.com> wrote:
>
> >>> >   * screenshot: http://i.stack.imgur.com/U9TFR.png
> >>> >   * unicorn.rb: https://gist.github.com/907th/4995323
> >> which command do you run to show that list?
> >
> > Screenshot? Its `htop` command with tree (F5) view.
>
>
> I have just one worker. If I run top I just see one master and one
> worker. But with htop there are 3 masters and 3 workers, each of them
> with a different pid. This is a surprise to me too. I'm runnnig ruby
> 1.9.2.
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Re: Why so many worker threads?

[Eric Wong]

Alexey Chernenkov <laise@pisem.net> wrote:
> 2013/3/1 Eric Wong <normalperson@yhbt.net>:
> > Alexey Chernenkov <laise@pisem.net> wrote:
> >>
> >> Can anyone explain why my Unicorn installation (for RoR site) have so
> >> many worker threads?
> >>   * screenshot: http://i.stack.imgur.com/U9TFR.png
> >>   * unicorn.rb: https://gist.github.com/907th/4995323
> >>
> >
> > It's probably some gem/library you're using which spawns threads behind
> > your back.  Ruby 1.9/2.0 only has one extra thread per-process for
> > accepting signals.
> >
> Could you advise me how I can determine which gem causes the problem?

What Tatsuya said.

Really, you should never hesitate to grep/scan/read the source of
_everything_ you're running.

For C extensions, check for the pthread_create() function, too.  Also,
any existing libraries your C/FFI extensions might link to...

If you're on Linux, you can probably track it down a little faster via
"strace -f -e clone"  (clone() is the underlying syscall used for both
fork() and pthread_create()).
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