FLY_HOSTING_GUIDE.md

Fly.io hosting guide

To ensure FerrumPdf works as expected in the Fly.io hosting environment, we need to make sure Chrome is installed via Docker and running with the --no-sandbox flag.

Dockerfile dependencies

First, add these dependencies to the Dockerfile used when deploying to Fly.io.

ENV DOCKER_BUILD=1
RUN apt-get update -qq && \
    DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
    chromium chromium-sandbox fonts-liberation libappindicator3-1 xdg-utils && \
    rm -rf /var/lib/apt/lists/* /var/cache/apt

I've also set DOCKER_BUILD, so the initializer is skipped when building the image (FerrumPdf will timeout since Chrome is not yet installed).

Initialize with options

Fly.io does not allow Chrome to run in sandbox mode, so we need to disable it.

# config/initializers/ferrum.rb

return if ENV['DOCKER_BUILD']

options = {
  process_timeout: 30,
  browser_options: {
    'no-sandbox' => nil
  }
}

options = options.merge(browser_path: '/usr/bin/chromium') if Rails.env.production?

FerrumPdf.browser(options)

Additionally, increasing the process timeout avoids code reloading issues in development as detailed here: Possibility to set Ferrum timeout to overcome code reloading issues in Development.

fly deploy these changes, confirm the build step succeeds and FerrumPdf generates pdfs as expected.