How to use Byebug with a remote process (e.g., pow)

Question

How do I connect to a remote debugging instance of Byebug (for use with Pow, etc)?

Orelee

Answer 1

In your code

remote_byebug

Invoke your code (e.g., by refreshing the page). This will spin up a local byebug server on port 8989. Your code will then 'hang' waiting for a client connection.

Connect to it via the terminal:

byebug -R localhost:8989

Manually configuring the server is no longer necessary as of https://github.com/deivid-rodriguez/byebug/pull/406/files

Invariable

Answer 2

Joseph's answer was good but confusing in some small ways. He places the starting of the byebug server in config/environments/development.rb, when it would be better in an initializer. Additionally the exporting of the environment variable go in .powenv or .powrc. This is how I got it to work.

In your gemfile:

gem 'byebug'

On the command line:

bundle install

If you are using Pow, add the following to .powenv:

export BYEBUGPORT=3001

If you are using other frameworks (e.g. just foreman), you may have to modify .env instead.

In config/initializers/byebug.rb

if Rails.env.development? and ENV['BYEBUGPORT']
  require 'byebug/core'
  Byebug.start_server 'localhost', ENV['BYEBUGPORT'].to_i
end

And finally on the command line:

touch tmp/restart.txt

Once you go to your pow site, the byebug server should be started. On the command line you can now do:

[bundle exec] byebug -R localhost:3001

Bludgeon

Yup, followed the instructions and it works like a charm. Thank you Nicholas! – Registration

Note that "touch tmp/restart.txt" may not be needed, depending on app server. Needed for Passenger in production, usually not needed in development on any app server. – Subclinical

Works nicely, also with puma-dev. Use ~/.powconfig instead of .powenv for global configuration. – Magdamagdaia

Answer 3

I had to piece together information from several different sources to accomplish the above, so I thought I'd include a consolidated guide here for convenience:

• https://github.com/deivid-rodriguez/byebug/pull/29,
• https://github.com/deivid-rodriguez/byebug/pull/36,
• https://github.com/deivid-rodriguez/byebug/issues/31
• http://mines.mouldwarp.com/2012/04/pow-guard-and-rdebug-staying-in-web-app.html

Here are the steps:

1. In config/environments/development.rb, add:

   require 'byebug'
   
   #set in your .powconfig
   if ENV['RUBY_DEBUG_PORT']
     Byebug.start_server 'localhost', ENV['RUBY_DEBUG_PORT'].to_i
   else
     Byebug.start_server 'localhost'
   end
   

2. Restart Pow and visit yourapp.dev

3. Run the following:

   [bundle exec] byebug -R localhost:<port_you_defined_in_pow_config>
   

You should see a successful connection to the remote instance.

Orelee

Thank you for this. I'm able to connect to the server, but my breakpoints aren't breaking. Any ideas? Places to start? Thanks! – Better

Are you using pow? If so, try the first answer in #8996998 – Orelee

I am using pow. I tried the answer, no luck. I'm sitting at a terminal with Connecting to byebug server localhost:12346. Connected. and lots of byebug calls in my code, but no breaking! I'm at a loss at this point - if you have any other ideas, I'm all ears! Otherwise, thank you anyhow for your help! – Better

Note: don't use the question Joseph mentions for Ruby 2.0 or higher! – Subclinical

@Noah could you please elaborate? – Orelee

@JosephSiefers sure. Ruby-debug (original) is 1.8 and lower only. Rdebug19 is still only through 1.9, no 2.0+. You have to use byebug instead of rdebug or rdebug19 for Ruby 2.0 or higher. Debuggers are fairly finicky extensions, they tend to break when Ruby changes the internals. – Subclinical

@Noah I see what you're getting at now, thanks for clarifying. Although that question references rdebug, it is still relevant and applies to byebug also under Ruby 2.0. The first response explains clearly that pow has multiple worker threads and it's possible that the remote debugger (in this case, byebug) will connect to the wrong thread (thus causing missed breakpoints). – Orelee

Note that you need to add require 'byebug/core' at the moment — see github.com/deivid-rodriguez/byebug/issues/… – Foretime