Capistrano 3 Task Argument Error - ruby-on-rails

Question

I'm using a capistrano 3 task that should work, but am getting the error:
> cap staging deploy --trace
** Invoke staging (first_time)
** Invoke use_rvm (first_time)
** Execute use_rvm
** Execute staging
** Invoke load:defaults (first_time)
** Execute load:defaults
cap aborted!
Task Argument Error
/Users/stevenspiel/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rake-10.4.2/lib/rake/task_manager.rb:109:in `resolve_args_with_dependencies'
/Users/stevenspiel/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rake-10.4.2/lib/rake/task_manager.rb:75:in `resolve_args'
/Users/stevenspiel/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rake-10.4.2/lib/rake/task_manager.rb:27:in `define_task'
/Users/stevenspiel/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rake-10.4.2/lib/rake/task.rb:365:in `define_task'
/Users/stevenspiel/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rake-10.4.2/lib/rake/dsl_definition.rb:66:in `task'
config/deploy.rb:65:in `<top (required)>'
...
the task is straightforward:
set :backup_to, '/home/deployer/app/db_backups'
desc 'Backup the remote production database'
task :backup_database, roles: :db, only: { primary: true } do
run "mkdir -p #{backup_to}" # create backup folder unless already exists
filename = "#{backup_to}/app_#{Time.now.strftime '%Y%m%d%H%M%S'}.sql.gz"
# Check if we've got database config
database_config = File.join(deploy_to, '/current/config/database.yml')
if remote_file_exists?(database_config)
text = capture("cat #{database_config}")
# `capture` is returning some bad whitespace that YAML::load can't handle.
# This strips out whitespace except for innocuous spaces and newlines.
text.gsub!(/[^\n \S]/, '')
config = YAML::load(text)[rails_env]
on_rollback { run "rm #{filename}" } # if migration rolls back, removes backup
run "pg_dump -U #{config['username']} #{config['database']} -W -h #{config['host']} | gzip --best > #{filename}" do |ch, stream, out|
ch.send_data "#{config['password']}\n" if out =~ /^Password:/
end
else
logger.debug('[BackupDatabase] No configuration file was found.')
end
end
before 'deploy:migrate', :backup_database if rails_env == 'staging'
And the error is coming from the task declaration:
task :backup_database, roles: :db, only: { primary: true } do
What is wrong with it?
EDIT
Thanks to basia's suggestion, I ended up doing this:
task :backup_database do
on roles(:app), except: { primary: true } do
...
end
end

Answer 1

You're using Capistrano 2 syntax and for Capistrano 3 the syntax is different than 2, have a look https://semaphoreapp.com/blog/2013/11/26/capistrano-3-upgrade-guide.html. Your code should look more like that (not tested):
task :backup_database do
roles(:db) do
.....
on
end
Or downgrade to Cap 2 :)