Configuring Caching in CircleCI - CircleCI Tutorial

Introduction

Configuring caching in CircleCI is a powerful technique to improve build performance by storing and reusing dependencies or intermediate artifacts across builds. By caching commonly used files, you can significantly reduce build times and improve the overall efficiency of your CI/CD pipeline. This tutorial will guide you through the steps of configuring caching in CircleCI.

Example

Let's consider an example where we want to cache the dependencies 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 test

Configuring Caching in CircleCI

To configure caching in CircleCI, follow these steps:

1. Define cache keys

Identify the files or directories that 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. 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 files if available. This step helps to avoid redundant installations. For example:

steps:

      - restore_cache:

        keys:

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

3. Save the cache

After installing dependencies or generating intermediate 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. For example:

steps:

      - save_cache:

        paths:

          - ./node_modules

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

Common Mistakes

Using incorrect cache keys or not updating them when dependencies change
Not specifying the correct paths to be cached
Over-caching unnecessary files or directories, leading to increased storage usage

Frequently Asked Questions (FAQs)

How can I check if the cache is being used in my builds?

You can enable verbose logging in CircleCI to see if the cache is being restored or saved during your builds. This can help you verify if the caching configuration is working correctly.
Can I cache multiple directories or files?

Yes, you can cache multiple directories or files by specifying multiple paths in the save_cache and restore_cache steps. Use a separate step for each path.
When should I update the cache key?

You should update the cache key whenever the content of the cached files or directories changes. Typically, this includes changes in dependency files, such as package-lock.json or requirements.txt.

Summary

In this tutorial, you learned how to configure caching in CircleCI to improve build performance. By defining cache keys, restoring caches, and saving caches, you can avoid redundant installations and speed up your CI/CD pipelines. Remember to fine-tune your caching strategy based on your project's specific dependencies and requirements. Refer to the CircleCI documentation for further details and advanced caching options.