Rails教程2.2：Puma服務器

Question

我正在嘗試從Rails教程書中學習Rails，獲得了lubuntu，所以我可以嘗試獲得最佳體驗。 現在，我堅持要簡單易行的東西。

我們正在創建一個“玩具應用”，一個非常基本的推特之類的東西，但仍然在一開始，我們就使用了：

$ rails generate scaffold User name:string email:string

如果我沒記錯的話，要生成一個用戶表，然后：

$ rails db:migrate

我猜想更新一個預先存在的表結構（不確定，但是據說稍后將進行解釋）。

最后，我們應該運行以下命令：

 $ rails server -b $IP -p $PORT

在一個差異選項卡中，我確實得到了這個錯誤：

~/workspace/toy_app$ rails server -b $IP -p $PORT
=> Booting Puma
=> Rails 5.0.0.1 application starting in development on http://-p:3000
=> Run `rails server -h` for more startup options
Puma starting in single mode...
* Version 3.4.0 (ruby 2.3.1-p112), codename: Owl Bowl Brawl
* Min threads: 5, max threads: 5
* Environment: development
* Listening on tcp://-p:3000
Exiting
/var/lib/gems/2.3.0/gems/puma-3.4.0/lib/puma/binder.rb:255:in `initialize': getaddrinfo: Name or service not known (SocketError)
    from /var/lib/gems/2.3.0/gems/puma-3.4.0/lib/puma/binder.rb:255:in `new'
    from /var/lib/gems/2.3.0/gems/puma-3.4.0/lib/puma/binder.rb:255:in `add_tcp_listener'
    from /var/lib/gems/2.3.0/gems/puma-3.4.0/lib/puma/binder.rb:102:in `block in parse'
    from /var/lib/gems/2.3.0/gems/puma-3.4.0/lib/puma/binder.rb:85:in `each'
    from /var/lib/gems/2.3.0/gems/puma-3.4.0/lib/puma/binder.rb:85:in `parse'
    from /var/lib/gems/2.3.0/gems/puma-3.4.0/lib/puma/runner.rb:129:in `load_and_bind'
    from /var/lib/gems/2.3.0/gems/puma-3.4.0/lib/puma/single.rb:84:in `run'
    from /var/lib/gems/2.3.0/gems/puma-3.4.0/lib/puma/launcher.rb:172:in `run'
    from /var/lib/gems/2.3.0/gems/puma-3.4.0/lib/rack/handler/puma.rb:51:in `run'
    from /var/lib/gems/2.3.0/gems/rack-2.0.1/lib/rack/server.rb:296:in `start'
    from /var/lib/gems/2.3.0/gems/railties-5.0.0.1/lib/rails/commands/server.rb:79:in `start'
    from /var/lib/gems/2.3.0/gems/railties-5.0.0.1/lib/rails/commands/commands_tasks.rb:90:in `block in server'
    from /var/lib/gems/2.3.0/gems/railties-5.0.0.1/lib/rails/commands/commands_tasks.rb:85:in `tap'
    from /var/lib/gems/2.3.0/gems/railties-5.0.0.1/lib/rails/commands/commands_tasks.rb:85:in `server'
    from /var/lib/gems/2.3.0/gems/railties-5.0.0.1/lib/rails/commands/commands_tasks.rb:49:in `run_command!'
    from /var/lib/gems/2.3.0/gems/railties-5.0.0.1/lib/rails/commands.rb:18:in `<top (required)>'
    from /home/zero/workspace/toy_app/bin/rails:9:in `require'
    from /home/zero/workspace/toy_app/bin/rails:9:in `<top (required)>'
    from /var/lib/gems/2.3.0/gems/spring-1.7.2/lib/spring/client/rails.rb:28:in `load'
    from /var/lib/gems/2.3.0/gems/spring-1.7.2/lib/spring/client/rails.rb:28:in `call'
    from /var/lib/gems/2.3.0/gems/spring-1.7.2/lib/spring/client/command.rb:7:in `call'
    from /var/lib/gems/2.3.0/gems/spring-1.7.2/lib/spring/client.rb:30:in `run'
    from /var/lib/gems/2.3.0/gems/spring-1.7.2/bin/spring:49:in `<top (required)>'
    from /var/lib/gems/2.3.0/gems/spring-1.7.2/lib/spring/binstub.rb:11:in `load'
    from /var/lib/gems/2.3.0/gems/spring-1.7.2/lib/spring/binstub.rb:11:in `<top (required)>'
    from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /home/zero/workspace/toy_app/bin/spring:13:in `<top (required)>'
    from bin/rails:3:in `load'
    from bin/rails:3:in `<main>'

有東西損壞了嗎？ 我做錯了嗎？ 我去檢查了我記得看到puma的文件（在app文件夾中），它在gem文件中：

gem 'puma',         '3.4.0'

和puma.rb文件（刪除注釋）：

threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }.to_i
threads threads_count, threads_count

port        ENV.fetch("PORT") { 3000 }

environment ENV.fetch("RAILS_ENV") { "development" }

plugin :tmp_restart

我本來要放所有提到的文件，但這是大量的代碼，如果有用的話，我會發布它，我不想用可能無用的代碼來發送垃圾郵件。

Answer 1

$IP在您的環境中未定義，因此rails server正在嘗試使用-p作為IP地址。 嘗試這個：

rails server -b ${IP:-127.0.0.1} -p ${PORT:-3000}

或者，在運行rails server -b $IP -p $PORT之前，使用export設置這些環境變量：

export IP=127.0.0.1
export PORT=3000

或者，如果您對Rails的默認設置感到滿意，則只需忘記所有這些並運行rails server 。 :-)

Answer 2

如果您在本地運行，則應該可以使用不帶參數的rails server 。 如果您使用的是Hartl教程，則假定您使用的是基於Web的IDE，該IDE需要額外的參數。

Answer 3

如果您使用的是cloud based IDE ，則需要收聽particular IP & PORT 。 例如， C9 ，您需要收聽0.0.0.0 and 8080 。 因此，它們具有設置environment variables, $IP & $PORT.

如果執行

echo $IP  ###gives 0.0.0.0
echo $PORT ###gives 8080

rails s -b $IP -p $PORT  ##Rails x.x.x application starting in development on http://0.0.0.0:8080

-b選項將Rails綁定到指定的IP，默認情況下為localhost。

如果您在本地計算機上，請運行

rails s ### Rails x.x.x application starting in development on http://localhost:3000