[DRAFT][Dockerfile] Leverage caching

[yelghali]

Often, the same image has to be rebuilt again & again with slight modifications in code.

Docker helps in such cases by storing the cache of each layer of a build.

Due to this concept, it’s recommended to add the lines which are used for installing dependencies & packages earlier inside the Dockerfile – before the COPY commands.

The reason behind this is that docker would be able to cache the image with the required dependencies, and this cache can then be used in the following builds when code gets modified

bad example
FROM ubuntu:latest
COPY . .
ENV DEBIAN_FRONTEND=noninteractive
RUN apt-get update -y
RUN apt-get upgrade -y
RUN apt-get install vim -y
RUN apt-get install net-tools -y
RUN apt-get install dnsutils -y

good example
FROM ubuntu:latest
ENV DEBIAN_FRONTEND=noninteractive
RUN apt-get update -y
RUN apt-get upgrade -y
RUN apt-get install vim -y
RUN apt-get install net-tools -y
RUN apt-get install dnsutils -y
COPY . .

To help you make your container smallers and more optimized, you can use tools like: https://github.com/slimtoolkit/slim