Docker Huddle - Reducing Build Time

Broadband Team - Daniel Deng (DiUS)

01. The problem

• A very trivial commit to master would trigger a pipeline that takes 20+ minutes.
• The feelback loop was very slow.
• Long running pipeline is blocking other pipelines

02. About the broadband-funnel app

• The broadband funnel consists of a backend-for-frontend bff and a front end fe
• bff is a Ruby 2.3.1 / Rails 5 application, API only.
• fe is React SPA

03. The previous docker solution

• 2 docker images based on ruby:2.3.1 image, one for bff one for fe
• Every time the pipeline runs, 2 docker images will be built.
• It used to about 20 mintues to build both images

04. What are the Dockerfiles doing?

bff:

• pull out ruby:2.3.1
• run apt-get update && apt-get upgrade
• install build time and runtime apt dependencies
• copy the whole /bff directory over
• switch WORKDIR
• run bundle install
• ENTRYPOINT / CMD

fe:

• pull out nginx:latest
• run apt-get update && apt-get upgrade
• install build time and runtime apt dependencies
• install node.js
• npm install -g yarn
• copy the whole /fe directory over
• switch WORKDIR
• yarn build to minimise the artefects
• copy nginx.conf
• ENTRYPOINT / CMD

05. Improvements

• use alpine instead
• combine to 1 docker image
• have a base image for time-consuming yet stable operations (apt-get, bundle install etc.)
• build the SPA artefect outside docker (e.g. in ci)
• delete build time dependencies

06. Outcome

ci docker build step duration reduced from 20+ minutes to 3 minutes

07. Further improvements

• non-root user
• use ENTRYPOINT more
• utilise caching further with the price of more layers
• update system packages even if Gemfile.lock doesn't change

08. Q&A / Comments