# Docker Huddle - Reducing Build Time
Broadband Team - Daniel Deng (DiUS)
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## 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 `Dockerfile`s 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