Resolving Docker Layer Caching (DLC) Teardown Errors in CircleCI

Overview

Docker Layer Caching (DLC) is a feature in CircleCI that can significantly reduce build times by reusing Docker image layers. However, issues can arise during the DLC Teardown step, indicated by a red step in the build history. This article explores the causes of such errors and provides guidance on how to address them.

Prerequisites

  • A CircleCI account and a project set up with Docker Layer Caching.
  • Basic understanding of Docker and CircleCI configuration.

Instructions

To diagnose and resolve issues with the DLC Teardown step, follow these steps

  1. Check if the Docker image was pruned during the DLC Teardown by listing the available Docker images at the start and end of the job:
steps:
- run:
name: List Docker images before build
command: docker image ls
- checkout
- run:
name: Build Docker image
command: docker image build --tag my-image --file Dockerfile .
- run:
name: List Docker images after build
command: docker image ls
  1. Compare the image IDs against what was pruned under DLC Teardown to verify if your built Docker image was affected.

  2. If you are using a VPN during your build, ensure to disconnect it after deployment to avoid interference with the DLC Teardown step.

Solution

The "context deadline exceeded" error during the DLC Teardown step is often related to network issues, such as an active VPN connection during the teardown process. To resolve this:

  • Add a step to disconnect from the VPN before the DLC Teardown step:

- run: 
    name: Disconnect VPN
    command: openvpn/disconnect
  • Ensure that your Docker images are within the DLC storage limit (currently at 15 GiB) to prevent them from being pruned.

Additional Resources

By following these steps and recommendations, you should be able to address the DLC Teardown errors and maintain a green build history.

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