Capistrano 3 failing with rails 5

Question

I have a rails 5 app (after upgrade) that uses the following capistrano 3.0 plugins:

  # Deployments
  gem 'capistrano', '~> 3.6'
  gem 'capistrano-rails', '~> 1.1'
  gem 'capistrano-bundler', '~> 1.1.2'
  gem 'capistrano-rbenv', '~> 2.0'
  gem 'capistrano-safe-deploy-to', '~> 1.1.1'
  gem 'capistrano-secrets-yml', '~> 1.0.0'
  gem 'capistrano-faster-assets', '~> 1.0'
  gem 'capistrano-ssh-doctor', '~> 1.0'
  gem 'capistrano-postgresql', '~> 4.1.0'
  gem 'capistrano-delayed-job', '~> 1.0'
  gem 'capistrano-unicorn-nginx', '~> 3.1.0'
  # gem 'capistrano-memcached', '~> 1.0'
  # gem 'capistrano-maintenance', github: "capistrano/maintenance", require: false

At the moment it seems that capistrano-rbenv is bummed out with rails 5.

$ cap production ssh:doctor --trace
** Invoke production (first_time)
** Execute production
** Invoke load:defaults (first_time)
** Execute load:defaults
** Invoke bundler:map_bins (first_time)
** Execute bundler:map_bins
** Invoke deploy:set_rails_env (first_time)
** Execute deploy:set_rails_env
** Invoke deploy:set_linked_dirs (first_time)
** Execute deploy:set_linked_dirs
** Invoke deploy:set_rails_env 
** Invoke rbenv:validate (first_time)
** Execute rbenv:validate
cap aborted!
NoMethodError: undefined method `on' for main:Object
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/capistrano-rbenv-2.0.4/lib/capistrano/tasks/rbenv.rake:3:in `block (2 levels) in <top (required)>'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:248:in `block in execute'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:243:in `each'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:243:in `execute'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:187:in `block in invoke_with_call_chain'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/2.3.0/monitor.rb:214:in `mon_synchronize'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:180:in `invoke_with_call_chain'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:173:in `invoke'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/capistrano-3.2.1/lib/capistrano/dsl/task_enhancements.rb:12:in `block in after'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:248:in `block in execute'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:243:in `each'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:243:in `execute'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:187:in `block in invoke_with_call_chain'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/2.3.0/monitor.rb:214:in `mon_synchronize'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:180:in `invoke_with_call_chain'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/task.rb:173:in `invoke'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/application.rb:152:in `invoke_task'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/application.rb:108:in `block (2 levels) in top_level'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/application.rb:108:in `each'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/application.rb:108:in `block in top_level'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/application.rb:117:in `run_with_threads'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/application.rb:102:in `top_level'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/application.rb:80:in `block in run'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/application.rb:178:in `standard_exception_handling'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/rake-11.2.2/lib/rake/application.rb:77:in `run'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/capistrano-3.2.1/lib/capistrano/application.rb:15:in `run'
/Users/admin/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/capistrano-3.2.1/bin/cap:3:in `<top (required)>'
/Users/admin/.rbenv/versions/2.3.1/bin/cap:23:in `load'
/Users/admin/.rbenv/versions/2.3.1/bin/cap:23:in `<main>'
Tasks: TOP => rbenv:validate

Has anyone else seen this issue?

Answer 1

It was a very simple fix:

Lock deploy.rb to version '3.6' and set :rbenv_ruby, '2.3.1' like so:

# config valid only for Capistrano 3.6
lock '3.6'

set :application, 'yourAppName'
set :repo_url, 'your gitlab url' 
set :deploy_to, '/var/www/yourAppName' # Default deploy_to directory is /var/www/my_app

set :pty, true # Default value for :pty is false

# CONFIGURATION: RBENV
# ==================
set :rbenv_type, :user # or :system, depends on your rbenv setup
set :rbenv_ruby, '2.3.1'
set :rbenv_prefix, "RBENV_ROOT=#{fetch(:rbenv_path)} RBENV_VERSION=#{fetch(:rbenv_ruby)} #{fetch(:rbenv_path)}/bin/rbenv exec"
set :rbenv_map_bins, %w(rake gem bundle ruby rails)
set :rbenv_roles, :all # default value