Caching Dependencies and Build Artifacts - CircleCI Tutorial

Introduction

Caching dependencies and build artifacts in CircleCI is a crucial technique to optimize build times and reduce the load on external resources. By caching frequently used dependencies and intermediate build artifacts, you can dramatically improve the performance of your CI/CD pipeline. This tutorial will guide you through the steps of caching dependencies and build artifacts in CircleCI.

Example

Let's consider an example where we want to cache the dependencies for a Node.js application and also cache the build artifacts:


    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/

Caching Dependencies and Build Artifacts

To cache dependencies and build artifacts 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. 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. 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)

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.
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.
When should I update the cache key?

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

Summary

In this tutorial, you learned how to cache dependencies and build artifacts 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 artifacts. Refer to the CircleCI documentation for further details and advanced caching options.