prod-server.html.md.erb

---
title: Production Server Configuration
owner: Buildpacks
---

<strong><%= modified_date %></strong>

This topic describes how to configure a production server for your apps. 

When you deploy an app, <%=vars.product_short%> determines the command used to start the app through the following process: 

1. If the developer uses the command `cf push -c COMMAND`, then <%=vars.product_short%> uses `COMMAND` to start the app. 

1. If the developer creates a file called a Procfile, <%=vars.product_short%> uses the Procfile to configure the command that launches the app. 
See the <a href="#procfile">About Procfiles</a> section below for more information.

1. If the developer does not use `cf push -c COMMAND` and does not create a Procfile, then <%=vars.product_short%> does one of the following, 
depending on the buildpack:
    + Uses a default start command.
    + Fails to start the app and shows a warning that the app is missing a Procfile.

##<a id="procfile"></a>About Procfiles

One reason to use a Procfile is specify a start command for buildpacks where a default start command is not provided. 
Some buildpacks, such as Python, that work on a variety of frameworks, do not attempt to provide a default start command.

Another reason to use a Procfile is to configure a production server for web apps.

A Procfile enables you to declare required runtime processes, called process types, for your web app. 
Process managers in a server use the process types to run and manage the workload. 
In a Procfile, you declare one process type per line and use the following syntax:

<pre class="code">
PROCESS_TYPE: COMMAND
</pre>

* `PROCESS_TYPE` is `web`. A `web` process handles HTTP traffic.
* `COMMAND` is the command line to launch the process.

For example, a Procfile with the following content starts the launch script created by the build process for a Java app:

```
web: build/install/MY-PROJECT-NAME/bin/MY-PROJECT-NAME
```

##<a id="specify-server"></a>Specify a Web Server

Follow these steps to specify a web server using a Procfile. 
For more information about configuring a web server for Rails apps, see the [Configure a Ruby Web Server](#config-ruby) section of this topic.

1. Create a blank file with a command line for a `web` process type. 

2. Save it as a file named `Procfile` with no extension in the root directory of your app. 

3. Push your app.

##<a id="config-ruby"></a>Configure a Ruby Web Server

<%=vars.product_short%> uses the default standard Ruby web server library WEBrick for Ruby and Ruby on Rails apps. 
However, <%=vars.product_short%> can support a more robust production web server, such as Phusion Passenger, Puma, Thin, or Unicorn.

To instruct <%=vars.product_short%> to use a web server other than WEBrick, perform the following steps: 

1. Add the gem for the web server to your Gemfile.

1. In the `config` directory of your app, create a new configuration file or modify an existing file. 
Refer to your web server documentation for how to configure this file. The following example uses the Puma web server:

    <pre class="code">
    &#35; config/puma.rb
    threads 8,32
    workers 3

    on_worker_boot do
      # things workers do
    end
</pre>

1. In the root directory of your app, create a Procfile and add a command line for a `web` process type that points to your web server.  
For information about configuring the specific command for a process type, see your web server documentation.<br/><br/>
    The following example shows a command that starts a Puma web server and specifies the app runtime environment, TCP port, and paths to the server state information and configuration files:
   
    <pre class="code">
    web: bundle exec puma -e $RAILS_ENV -p 1234 -S ~/puma -C config/puma.rb
    </pre>