Bundler如何判定需要重新安装Ruby Gem组件？

Got it, let's get your CircleCI builds caching Ruby gems properly so you don't have to reinstall them every time. Here's a step-by-step guide tailored to your current setup:

Ruby gems installed via Bundler can be cached in the vendor/bundle directory (we'll configure Bundler to use this path instead of the system default) — this makes it easy for CircleCI to pick up and store the cached files between builds.

You'll need to modify your .circleci/config.yml to add cache restoration and saving steps. Here's a complete example that aligns with your current build commands:

version: 2.1
jobs:
  build:
    docker:
      - image: circleci/ruby:2.6.3 # Replace with your project's Ruby version
    steps:
      - checkout

      # Restore cached gems if they exist
      - restore_cache:
          keys:
            # Use the Gemfile.lock checksum to ensure cache only reuses matching dependencies
            - gems-v1-{{ checksum "Gemfile.lock" }}
            # Fallback to a generic cache key if the exact one doesn't exist
            - gems-v1-

      # Install Bundler (match the version you're using)
      - run:
          name: Install Bundler
          command: gem install bundler -v 1.16.1

      # Install gems to the vendor/bundle directory for caching
      - run:
          name: Install Ruby Gems
          command: bundle install --path vendor/bundle

      # Save the gem cache for future builds
      - save_cache:
          paths:
            - vendor/bundle
          key: gems-v1-{{ checksum "Gemfile.lock" }}

      # Add your other build steps here (e.g., tests, linting)

After pushing this config to your repo, trigger a new build:

• The first build will still run bundle install and download all your gems (like nokogiri 1.8.2 with native extensions) as usual, but it will save the vendor/bundle directory to CircleCI's cache at the end.
• On subsequent builds, you'll see a "Restoring cache" step in the CircleCI logs. Then, when running bundle install, you'll notice lines like Using public_suffix 3.0.2 instead of Fetching public_suffix 3.0.2 — that means the cache is working, and gems are being reused instead of reinstalled.

If you update your Gemfile or Gemfile.lock later, the {{ checksum "Gemfile.lock" }} part will generate a new cache key. CircleCI will then download the updated dependencies and create a new cache, so you don't have to worry about stale cache when your dependencies change.

内容的提问来源于stack exchange，提问作者James Ives