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Make Dockerfile Deploy faster by structuring your Dockerfile to maximize efficiency by leveraging the Docker build cache:

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Gems installed via Bundler

In order for the Docker build cache to cache gems installed via Bundler:
  1. Add the Gemfile and Gemfile.lock files to the image.
  2. Run bundle install, before adding the rest of the repo (via ADD .).
Here’s an example of how that might look in a Dockerfile: 
FROM ruby

# If needed, install system dependencies here

# Add Gemfile and Gemfile.lock first for caching
ADD Gemfile /app/
ADD Gemfile.lock /app/
WORKDIR /app
RUN bundle install

ADD . /app

# If needed, add additional RUN commands here

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Packages installed via NPM

In order for the Docker build cache to cache packages installed via npm:
  1. Add the package.json file to the image.
  2. Run npm install, before adding the rest of the repo (via ADD .).
Here’s an example of how that might look in a Dockerfile: 
FROM node

# If needed, install system dependencies here

# Add package.json before rest of repo for caching
ADD package.json /app/
WORKDIR /app
RUN npm install

ADD . /app

# If needed, add additional RUN commands here

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Packages installed via PIP

In order for the Docker build cache to cache packages installed via pip:
  1. Add the requirements.txt file to the image.
  2. Run pip install, before adding the rest of the repo (via ADD .).
Here’s an example of how that might look in a Dockerfile: 
FROM python

# If needed, install system dependencies here

# Add requirements.txt before rest of repo for caching
ADD requirements.txt /app/
WORKDIR /app
RUN pip install -r requirements.txt

ADD . /app