Cannot connect to process running in Phusion Passenger

[kmile]

I am trying to perform an rbtrace on a Rails app running in Phusion Passenger. If I execute a long running rake task it can connect just fine. If I connect it to the corresponding Passenger Process it tells me (pid is not listening for messages, did you require "rbtrace").

I have required rbtrace in the environment.rb. Passenger runs in production mode, and I am using REE 1.8.7. Is there any reason rbtrace would not work for a Passenger process?

[tmm1]

passenger removes all signal handlers on startup. try require 'rbtrace' inside a before filer on ApplicationController instead.

[jodell]

I'm having the same issue under Sinatra. I've tried instrumenting the require statement in a controller action, app load, and the rackup file independently but it doesn't take. A simple ruby script works with rbtrace on the same machine. Using ruby 1.9.2 and passenger 3.0.6.

[tmm1]

If you're using gem 'rbtrace' in a Gemfile, rbtrace will be loaded before passenger forks. You need to make sure it is loaded in the controller action (require should return true)

[jodell]

Unblocked, thanks! This also reminds me of the value of Bundler's 'require => false' option.

[balepc]

Still have a problem connecting to passenger instance :( It says
Error: argument --pid (pid is not listening for messages, did yourequire "rbtrace").

But, I've required it in before_filter and in envrionment.rb

[tmm1]

You need to ensure it is only required in the before_filter. Remove from environment.rb and make sure the Gemfile says :require => false

[saadbinakhlaq]

Hi @tmm1 I am following up on this blog http://blog.skylight.io/hunting-for-leaks-in-ruby/, I have created an endpoint in admin namespace and request that endpoint I am getting this error in the logs
Error: argument --pid (process already being traced?).
Error: argument --pid (pid is not listening for messages, did you require "rbtrace").
this is like alternating

my configuration
Gemfile
gem 'rbtrace', require: false

controller.rb file

class Admin::InvestigationsController < AdminController
  defaults resource_class: User
  def memory
    system("rbtrace -p #{Process.pid} -e 'load \"#{Rails.root}/script/heap_dump.rb\"'")
  end
end

initializers/users.rb

require 'rbtrace'

This setup worked fine if I ran rbtrace from the console but I am getting the above errors when I run it from the endpoint.

it would be great if you would please have a look

Thanks

[dmitry]

It works well then using gem 'rbtrace', require: false and then require 'rbtrace' somewhere in before_filter (for example, in ApplicationController). Looks like can be closed, but noticed somewhere in the README.

[glh1991]

I am trying to perform an rbtrace on a Rails app running in puma, add gem 'rbtrace', '~> 0.4.7', require: false in Gemfile, and add require 'rbtrace' in config/environment.rb. then what should i do for listenning the pid.
Thanks

[swapab]

@kmile were you able to make rbtrace work with passenger ?

I am having a hard luck in rbtraceing mine.

1.Added controller action to get a heap dump

  def dump
    require 'rbtrace'
    pid = Process.pid
    Rails.logger.debug("Process.pid: #{pid}")
    system("rbtrace -p #{pid} -e 'Thread.new{require \"objspace\"; ObjectSpace.trace_object_allocations_start; GC.start(); ObjectSpace.dump_all(output: File.open(\"/tmp/dump/heap_dump_#{params[:id]}.json\", \"w\"))}.join'")
    head :ok
  end

2.required rbtrace before each action

  before_filter :require_rbtrace

  def require_rbtrace
    require 'rbtrace'
  end

3.In boot.rb --> require 'rbtrace'

4.Call the dump action https://bingdev.bingoa.com/api/feeds/dump?id=11

---

Still see Error: argument --pid (pid is not listening for messages, did you require "rbtrace")

App 17680 stderr: Error: argument --pid (pid is not listening for messages, did you `require "rbtrace"`).
App 17680 stderr: Try --help for help.

[shellandbull]

Getting the same issue as @swapnilabnave I'm using Rails 4.0.6

[swapab]

@mariogintili
I switched to memory_profiler which uses ObjectSpace to profile memory per request.

It helped me pin down leaks in my application.

[meetme2meat]

@tmm1 I getting the same error. But the only difference for me is that I'm using rbtrace on a standalone ruby application.

[locofocos]

I was having this same issue- the given pid was not listening for messages. What ultimately worked for me was putting the code from the Thread.new command into a controller method by itself:

def memory_dump
    GC.start
    require 'objspace'
    io=File.open('/tmp/ruby-heap.dump', 'w')
    ObjectSpace.dump_all(output: io)
    io.close

    render text: 'Memory dump complete!'
end

then I created a route to this action and navigated to it in my browser. This completed successfully.

[ejholmes]

For anyone running into this issue, the correct way to use rbtrace with recent versions of passenger is to require it within the after_installing_signal_handlers hook:

# config.ru
PhusionPassenger.on_event(:after_installing_signal_handlers) do
  require 'rbtrace'
end

If you require it earlier, passenger resets all signal handlers after fork, which removes the SIGURG handler that rbtrace installs.

[zw963]

For anyone running into this issue, the correct way to use rbtrace with recent versions of passenger is to require it within the after_installing_signal_handlers hook:

# config.ru
PhusionPassenger.on_event(:after_installing_signal_handlers) do
  require 'rbtrace'
end

If you require it earlier, passenger resets all signal handlers after fork, which removes the SIGURG handler that rbtrace installs.

It working. passenger 6.0.2, ruby 2.6.1

[gbxl]

Is that before or after the run Rails.application? I have tired both, with passenger 6.0.2 and no dice.
I tired both the main passenger PID as well as individual workers' pid :(

---

After adding require: false in Gemfile it works!
For posterity, here is the full setup:
passenger 6.0.2
rails (6.0.1)
ruby 2.5.0p0

In gemfile:
gem 'rbtrace', require: false

In config.ru, at the very top:

PhusionPassenger.on_event(:after_installing_signal_handlers) do
  require 'rbtrace'
end

[pgouv]

It doesnt work for me too.
I get Error: argument --pid (process already being traced?).

Passenger 5.1.12 and ruby 2.4.0

[krunde-nextpoint]

I am getting the same error "argument --pid (process already being traced?)" as well. I am on:
Passenger: 6.0.3
Ruby: 2.6.6
Rails: 5.2.4.4
Nginx: 1.17.10