缺少mysql2寶石錯誤時，Capistrano的部署

Question

版本
導軌 - 4.2.0
Capistrano的 - 3.4.0
紅寶石 - 2.2.2

我試圖部署應用到生產與Capistrano的，但不斷收到此錯誤：

[42ad5e96] Command: cd ~/deploy/my-app/releases/20151203212725 && (RAILS_ENV=production ~/.rvm/bin/rvm default do bundle exec rake assets:precompile) 
DEBUG [42ad5e96]  rake aborted! 
DEBUG [42ad5e96]  Gem::LoadError: Specified 'mysql2' for database adapter, but the gem is not loaded. Add `gem 'mysql2'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord). 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_adapters/connection_specification.rb:177:in `rescue in spec' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_adapters/connection_specification.rb:174:in `spec' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_handling.rb:50:in `establish_connection' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/railtie.rb:120:in `block (2 levels) in <class:Railtie>' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/lazy_load_hooks.rb:38:in `instance_eval' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/lazy_load_hooks.rb:38:in `execute_hook' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/lazy_load_hooks.rb:28:in `block in on_load' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/lazy_load_hooks.rb:27:in `each' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/lazy_load_hooks.rb:27:in `on_load' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/railtie.rb:116:in `block in <class:Railtie>' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/initializable.rb:30:in `instance_exec' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/initializable.rb:30:in `run' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/initializable.rb:55:in `block in run_initializers' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/initializable.rb:54:in `run_initializers' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/application.rb:352:in `initialize!' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/releases/20151203212725/config/environment.rb:5:in `<top (required)>' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `block in require' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:240:in `load_dependency' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/application.rb:328:in `require_environment!' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/application.rb:443:in `block in run_tasks_blocks' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/sprockets-rails-2.3.3/lib/sprockets/rails/task.rb:64:in `block (2 levels) in define' 
DEBUG [42ad5e96]  Gem::LoadError: mysql2 is not part of the bundle. Add it to Gemfile. 
DEBUG [42ad5e96]  /home/xxx/.rvm/gems/ruby-2.2.2/gems/bundler-1.10.6/lib/bundler/rubygems_integration.rb:292:in `block in replace_gem' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_adapters/mysql2_adapter.rb:3:in `<top (required)>' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `block in require' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:240:in `load_dependency' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/ge 
DEBUG [42ad5e96]  ms/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_adapters/connection_specification.rb:175:in `spec' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_handling.rb:50:in `establish_connection' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/railtie.rb:120:in `block (2 levels) in <class:Railtie>' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/lazy_load_hooks.rb:38:in `instance_eval' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/lazy_load_hooks.rb:38:in `execute_hook' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/lazy_load_hooks.rb:28:in `block in on_load' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/lazy_load_hooks.rb:27:in `each' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/lazy_load_hooks.rb:27:in `on_load' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activerecord-4.2.0/lib/active_record/railtie.rb:116:in `block in <class:Railtie>' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/initializable.rb:30:in `instance_exec' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/initializable.rb:30:in `run' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/initializable.rb:55:in `block in run_initializers' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/initializable.rb:54:in `run_initializers' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/application.rb:352:in `initialize!' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/releases/20151203212725/config/environment.rb:5:in `<top (required)>' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `block in require' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:240:in `load_dependency' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:274:in `require' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/application.rb:328:in `require_environment!' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/application.rb:443:in `block in run_tasks_blocks' 
DEBUG [42ad5e96]  /home/xxx/deploy/my-app/shared/bundle/ruby/2.2.0/gems/sprockets-rails-2.3.3/lib/sprockets/rails/task.rb:64:in `block (2 levels) in define' 

這裏是我的Gemfile：

source 'https://rubygems.org' 


# Bundle edge Rails instead: gem 'rails', github: 'rails/rails' 
gem 'rails', '4.2.0' 
# Use mysql as the database for Active Record 
gem 'mysql2', '~> 0.3.20' 
#gem 'pg' 
# Use SCSS for stylesheets 
gem 'sass-rails', '~> 5.0' 
gem 'sass', '~> 3.4', '>= 3.4.19' 
gem 'bourbon', '~> 4.2', '>= 4.2.6' 
# Use Uglifier as compressor for JavaScript assets 
gem 'uglifier', '>= 1.3.0' 
# Use CoffeeScript for .coffee assets and views 
#gem 'coffee-rails', '~> 4.1.0' 
# Simple Forms gem 
gem 'simple_form' 
# Handle File Uploads 
gem 'paperclip', '~> 4.3' 
# Use jquery as the JavaScript library 
gem 'jquery-rails' 
# User management gem 
gem 'devise' 
# User permissions/abilities gem 
gem 'cancancan' 
# Access HTTP and REST resources 
gem 'rest-client' 
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder 
gem 'jbuilder', '~> 2.0' 
# bundle exec rake doc:rails generates the API under doc/api. 
gem 'sdoc', '~> 0.4.0', group: :doc 

gem 'pry', '~> 0.10.3' 
# Use ActiveModel has_secure_password 
# gem 'bcrypt', '~> 3.1.7' 

# Use Passenger as the app server 
gem 'passenger' 

gem 'faraday' 

group :development, :test do 
    # Call 'byebug' anywhere in the code to stop execution and get a debugger console 
    gem 'byebug' 

    gem 'capistrano' 
    gem 'capistrano-rvm' 
    gem 'capistrano-rails' 
    gem 'capistrano-passenger' 
    # Access an IRB console on exception pages or by using <%= console %> in views 
    gem 'web-console', '~> 2.0' 

    # Test-Driven-Development enabler 
    gem 'rspec' 

    gem 'awesome_print' 
end 

的database.yml

default: &default 
    adapter: mysql2 
    encoding: utf-8 
    host: 127.0.0.1 
    username: username 
    password: password 
    pool: 5 
    timeout: 5000 

development: 
    <<: *default 
    database: dev_deb 

# Warning: The database defined as "test" will be erased and 
# re-generated from your development database when you run "rake". 
# Do not set this db to the same as development or production. 
test: 
    <<: *default 
    database: 

production: 
    <<: *default 
    database: prod_db 

Answer 1

gem 'mysql2', '~> 0.3.18'作品與軌道版本4.x.x。

因此，將您的mysql2寶石降級到版本'~> 0.3.18'。

在你Gemfile：

gem 'mysql2', '~> 0.3.18' 

然後做：

bundle install