Setup Rails on unicorn on nginx on AWS EC2 linux

## How to install Unicorn
### 1.Modify Gemfile contents
```
$ sudo vim ~/(sampleapp)/Gemfile
```
Add `gem 'unicorn'`

###2. Install unicorn at the Gemfile's directory
`$ bundle install`
###3. Check installation of unicorn  
```
$ bundle show unicorn
/home/ec2-user/.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0
```
###4. Make "unicorn.rb" on /(sampleAppDirectory)/config and write following contents

  ```unicorn.rb
  worker_processes Integer(ENV["WEB_CONCURRENCY"] || 3)
  timeout 15
  preload_app true

  listen '/home/ec2-user/testApp/tmp/unicorn.sock' #{Railsアプリケーションのあるディレクトリ}/tmp/unicorn.sock
  pid    '/home/ec2-user/testApp/tmp/unicorn.pid' #{Railsアプリケーションのあるディレクトリ}/tmp/unicorn.pid

  before_fork do |server, worker|
    Signal.trap 'TERM' do
      puts 'Unicorn master intercepting TERM and sending myself QUIT instead'
      Process.kill 'QUIT', Process.pid
    end

    defined?(ActiveRecord::Base) and
      ActiveRecord::Base.connection.disconnect!
  end

  after_fork do |server, worker|
    Signal.trap 'TERM' do
      puts 'Unicorn worker intercepting TERM and doing nothing. Wait for master to send QUIT'
    end

    defined?(ActiveRecord::Base) and
      ActiveRecord::Base.establish_connection
  end

  stderr_path File.expand_path('log/unicorn.log', ENV['RAILS_ROOT'])
  stdout_path File.expand_path('log/unicorn.log', ENV['RAILS_ROOT'])
  ```
###5. Execute following code and create rake file at your app directory
```
$ rails g task unicorn 
Running via Spring preloader in process 13140
      create  lib/tasks/unicorn.rake
```
###6. Start unicorn and check unicorn starting
```
$ bundle exec unicorn_rails -c config/unicorn.rb 

```
*↑production環境かdeployment環境は選べる。Unicorn commands一覧参照

```
$ ps -ef | grep unicorn
ec2-user 12631 11576  0 08:09 pts/1    00:00:00 vim unicorn.rb
ec2-user 13547 13151  0 08:37 pts/5    00:00:01 unicorn master -c config/unicorn.rb                                                                                            
ec2-user 13582 13547  0 08:37 pts/5    00:00:00 unicorn worker[0] -c config/unicorn.rb                                                                                         
ec2-user 13584 13547  0 08:37 pts/5    00:00:00 unicorn worker[1] -c config/unicorn.rb                                                                                         
ec2-user 13587 13547  0 08:37 pts/5    00:00:00 unicorn worker[2] -c config/unicorn.rb                                                                                         
ec2-user 14665 13960  0 08:51 pts/3    00:00:00 grep --color=auto unicorn
```

## Modify the setting of Nginx
###1. Modify nginx.conf to rails.cof
nginx/1.10.2時点ではnginx.conf(`$ nginx -t`でconfigファイルを確認できる)。nginx.confに以下のように書き換える。

```nginx.conf
# For mor# e information on configuration, see:
#   * Official English Documentation: http://nginx.org/en/docs/
#   * Official Russian Documentation: http://nginx.org/ru/docs/

user ec2-user;
worker_processes 1;

events {
    worker_connections 1024;
}

http {
#    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
#                     '$status $body_bytes_sent "$http_referer" '
#                      '"$http_user_agent" "$http_x_forwarded_for"';

#   access_log  /home/ec2-user/testApp/access.log  main;

#    sendfile            on;
#    tcp_nopush          on;
#    tcp_nodelay         on;
#    keepalive_timeout   65;
#    types_hash_max_size 2048;

#    include             /etc/nginx/mime.types;
#    default_type        application/octet-stream;

    # Load modular configuration files from the /etc/nginx/conf.d directory.
    # See http://nginx.org/en/docs/ngx_core_module.html#include
    # for more information.
#   include /etc/nginx/conf.d/*.conf;

#   index   index.html index.htm;

    upstream unicorn {
      server  unix:/home/ec2-user/testApp/tmp/unicorn.sock; #/home/{ユーザ名}/{Railsアプリケーション>名}/tmp/unicorn.sock
    }

    server {
        listen       xx; #HTTP = 80
        server_name  xxx.xxx.xxx.xxx; #Your server ip-address or domain name

        access_log  /var/log/access.log;
        error_log   /var/log/error.log;

        root    /home/ec2-user/testApp/public; #/home/{ユーザ名}/{Railsアプリケーション名}/public
#       index   index.html;
        client_max_body_size 4G; #100m;
        error_page  404              /404.html;
        error_page  500 502 503 504  /500.html;
        try_files   $uri/index.html $uri @unicorn;

        location @unicorn {
                proxy_set_header X-Real-IP $remote_addr;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header Host $http_host;
                proxy_pass http://unicorn;
                }

        }
```

###2. Reload nginx  
```
$ sudo service nginx restart
```

###3. Access your server address!!!

##ここからはunicornのnginxに対するpermission deniedが出た時の処理
```
2017/04/23 06:45:40 [crit] 29912#0: *1 open()
"/var/lib/nginx/tmp/proxy/1/00/0000000001" failed (13: Permission
denied) while reading upstream, client: (clientserver), server:
(my-server), request: "GET / HTTP/1.1", upstream:
"http://unix:/pathTo/tmp/unicorn.sock:/", host:
"(my-server)"
```

上記エラーではnginx, tmpにおけるアクセス権限がnginxのみしかないので、アクセス権を解放する(下記アクセスは777としているが修正する必要あり)

```
$ sudo chmod 777 nginx
$ sudo chmod 777 tmp
```