Cache Management and Invalidation - CircleCI Tutorial

Introduction

Cache management and invalidation are critical aspects of maintaining the integrity and freshness of dependencies and build artifacts in CircleCI. Caches need to be managed effectively to ensure that outdated or incorrect data is not used during the CI/CD process. This tutorial will guide you through the steps of cache management and invalidation in CircleCI.

Example

Let's consider an example where we want to manage and invalidate the cache for a Node.js application:


    version: 2.1

    jobs:

      build:

        docker:

          - image: circleci/node:12

        steps:

          - checkout

          - restore_cache:

            keys:

              - v1-dependencies-{{ checksum "package-lock.json" }}

          - run: npm install

          - save_cache:

            paths:

              - ./node_modules

            key: v1-dependencies-{{ checksum "package-lock.json" }}

          - run: npm build

          - store_artifacts:

            path: dist/

Cache Management and Invalidation

To manage and invalidate caches in CircleCI, follow these steps:

1. Define cache keys

Identify the dependencies or files you want to cache and generate cache keys based on their content. Use the keys attribute in the restore_cache and save_cache steps to specify the cache keys. The cache keys should be unique and correspond to the content being cached. For example:

steps:

      - restore_cache:

        keys:

          - v1-dependencies-{{ checksum "package-lock.json" }}

2. Restore the cache

Before installing dependencies or executing build steps, restore the cache using the restore_cache step. CircleCI will attempt to find a matching cache key and restore the cached dependencies or files if available. This step helps to avoid redundant installations or downloads. For example:

steps:

      - restore_cache:

        keys:

          - v1-dependencies-{{ checksum "package-lock.json" }}

3. Save the cache

After installing dependencies or generating build artifacts, save the cache using the save_cache step. Specify the paths to be cached and provide a cache key that uniquely identifies the cache content. This step ensures that the cache is updated with the latest dependencies or artifacts. For example:

steps:

      - save_cache:

        paths:

          - ./node_modules

        key: v1-dependencies-{{ checksum "package-lock.json" }}

4. Cache invalidation

To invalidate the cache and force a fresh download or installation of dependencies, you can modify the cache key used in the restore_cache and save_cache steps. By changing the cache key, CircleCI will treat it as a new cache and fetch the latest dependencies or files. Common cache invalidation strategies include updating the cache key when dependency files change or at regular intervals to ensure freshness.

Common Mistakes

Using incorrect cache keys or not updating them when dependencies change
Not specifying the correct paths to be cached
Forgetting to update the cache key for cache invalidation

Frequently Asked Questions (FAQs)

How often should I invalidate the cache?

The frequency of cache invalidation depends on your project's requirements. It is common to invalidate the cache when dependency files change or at regular intervals to ensure the latest dependencies are used.
Can I manually clear the cache?

CircleCI provides an option to manually clear caches for a specific job or workflow. You can do this through the CircleCI web interface or using the CircleCI API.
What happens if the cache is not available?

If the cache is not available or cannot be restored, CircleCI will fallback to installing the dependencies or generating the artifacts from scratch. This may increase the build time.

Summary

In this tutorial, you learned how to manage and invalidate caches in CircleCI to ensure the freshness of dependencies and build artifacts. By defining cache keys, restoring caches, and saving caches, you can optimize build times and maintain the integrity of your CI/CD pipelines. Remember to implement appropriate cache invalidation strategies based on your project's requirements. Refer to the CircleCI documentation for further details and advanced caching options.