A Procfile is a mechanism for declaring what commands are run by your application’s containers on the Deis platform. It follows the process model. You can use a Procfile to declare various process types, such as multiple types of workers, a singleton process like a clock, or a consumer of the Twitter streaming API.
A Procfile is a text file named
Procfile placed in the root of your application that lists the
process types in an application. Each process type is a declaration of a command that is executed
when a container of that process type is started.
All the language and frameworks using Heroku’s Buildpacks declare a
web process type, which starts the application server. Rails 3 has the following process type:
web: bundle exec rails server -p $PORT
All applications using Dockerfile deployments have an implied
process type, which spawns the default process of a Docker image:
$ cat Dockerfile FROM centos:latest COPY . /app WORKDIR /app CMD python -m SimpleHTTPServer 5000 EXPOSE 5000
For applications using Docker image deployments, a
type is also implied and spawns the default process of the image.
Process types are declared via a file named
Procfile, placed in the root of your app. Its
format is one process type per line, with each line containing:
<process type>: <command>
The syntax is defined as:
<process type> – an alphanumeric string, is a name for your command, such as web, worker, urgentworker, clock, etc.
<command> – a command line to launch the process, such as
The web and cmd process types are special as they’re the only process types that will receive HTTP traffic from Deis’s routers. Other process types can be named arbitrarily.
Procfile is not necessary to deploy most languages supported by Deis. The platform
automatically detects the language and supplies a default
web process type to boot the server.
Creating an explicit Procfile is recommended for greater control and flexibility over your app.
For Deis to use your Procfile, add the Procfile to the root of your application, then push to Deis:
$ git add . $ git commit -m "Procfile" $ git push deis master ... -----> Procfile declares process types: web, worker Compiled slug size is 10.4MB Launching... done, v2 -----> unisex-huntress deployed to Deis http://unisex-huntress.example.com
For Docker image deployments, a Procfile in the current directory or specified by
deis pull --procfile will define the default process types for the application.
deis scale web=3 to increase
web processes to 3, for example. Scaling a
process type directly changes the number of Containers
running that process.
When deploying to Deis using a Heroku Buildpack, Deis boots the
web process type to boot the
application server. When you deploy an application that has a Dockerfile or uses Docker
images, Deis boots the
cmd process type. Both act similarly in that they
are exposed to the router as web applications. However, The
cmd process type is special because
it is equivalent to running the Container without any additional arguments. Every other
process type is equivalent to running the relevant command that is provided in the Procfile.
When migrating from Heroku Buildpacks to a Docker-based deployment, Deis will not convert
process types to
cmd. To do this, you’ll have to manually scale down the old process type and
scale the new process type up.