Runtime Creation

Runtimes are a core concept in FaaSO. They contain all the bits that are missing from a Funko to turn it into a complete application, and thus are the thing that gives a Funko its illusion of simplicity.

What is a runtime

• A folder.
• With files.
• With a template subfolder.
• Which combined with a Funko produces a container.

Let's look at the flask runtime as an example:

> tree flask
flask
├── Dockerfile.j2
├── main.py
├── README.md
└── template
    ├── funko.py.j2
    ├── funko.yml.j2
    ├── public
    │   └── index.html
    └── requirements.txt

The template Folder

When the user says faaso new -r flask myapp, faaso:

• Creates a new folder myapp.
• Copies the contents of flask/template into myapp.
• All files that are .j2 are rendered with {{name}} replaced with myapp.

How are runtimes used

When the user says faaso build myapp, faaso:

• Creates a temporary folder.
• Copies the contents of the runtime into the temporary folder.
• Files with .j2 extension are rendered using myapp/funko.yml as context.

For example, a funko.yml might look like this:

name: historico
runtime: kemal
options:
  shard_build_options: ""
  ship_packages: ["curl", "fish"]
  devel_packages: []
  healthcheck_options: "--interval=1m --timeout=2s --start-period=2s --retries=3"
  healthcheck_command: "curl --fail http://localhost:3000/ping || exit 1"

ARG BUILDPLATFORM
FROM --platform=${BUILDPLATFORM:-foobar} alpine AS build
RUN apk add --no-cache \
    crystal \
    shards \
    openssl-dev \
    zlib-dev {{ options.ship_packages | join(" ") }} {{ options.devel_packages | join(" ") }}

ARG BUILDPLATFORM
FROM --platform=${BUILDPLATFORM:-foobar} alpine AS build
RUN apk add --no-cache \
    crystal \
    shards \
    openssl-dev \
    zlib-dev curl fish

How to create a new runtime

Create a basic application using the language and framework of your choise. Add a Dockerfile such that it builds the app and runs it in port 3000

Then, for each file, decide whether the user needs to care for it or not. If the user should care, put it in template

Then, for each file, rename as filename.j2 and replace the parts that should be configured with jinja expressions to generate them.

Finally, create:

• README.md describing the thing. Put a descriptive title in the 1st line.
• template/funko.yml.j2 with the default configuration for a funko using your runtime.

For example, in the kemal runtime, the funko.yml.j2 looks like this:

name: {{ name }}
runtime: {{ runtime }}
options:
  shard_build_options: "--release"
  ship_packages: []
  devel_packages: []
  healthcheck_options: "--interval=1m --timeout=2s --start-period=2s --retries=3"
  healthcheck_command: "curl --fail http://localhost:3000/ping || exit 1"

If you think it would be useful for others, feel free to create a PR adding it to the runtimes folder in the main repository.