What are the best practices for using Docker cache in CircleCI?

What are the best practices for using Docker cache in CircleCI?

To optimize Docker builds in CircleCI, you should leverage caching effectively. Here are some best practices:

1. Use a multi-stage build to minimize the final image size.
2. Cache dependencies separately to avoid rebuilding them every time.
3. Utilize CircleCI's built-in caching features to store Docker layers.

How can I set up caching in my CircleCI config?

You can set up caching in your CircleCI config by using the save_cache and restore_cache steps. Here's a basic example:

version: 2.1
jobs:
  build:
    docker:
      - image: circleci/python:3.8
    steps:
      - checkout
      - restore_cache:
          keys:
            - v1-dependencies-{{ checksum "requirements.txt" }}
      - run:
          name: Install dependencies
          command: pip install -r requirements.txt
      - save_cache:
          paths:
            - .venv
          key: v1-dependencies-{{ checksum "requirements.txt" }}

What should I avoid when using Docker cache?

Avoid caching files that change frequently, as this can lead to cache invalidation and longer build times. Also, be cautious with sensitive data; do not cache secrets or credentials.

Can you give me an example of a multi-stage build?

Sure! Here's a simple example of a multi-stage Dockerfile:

# Stage 1: Build
FROM node:14 AS build
WORKDIR /app
COPY package.json .
RUN npm install
COPY . .
RUN npm run build

# Stage 2: Production
FROM nginx:alpine
COPY --from=build /app/build /usr/share/nginx/html
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]