Not caching ECR images used for job runs

The Caching docs says:

Note: The Docker images used for CircleCI 2.0 job runs are automatically cached on the server infrastructure where possible.

But in the Spin up Environment step of the build, we always got this:

Build-agent version 0.1.1480-7a5183d3 (2019-01-22T18:14:45+0000)
Starting container
  image cache not found on this host, downloading

Is this correct? There is some particular requirement for images to be cached?


Hello @hugomaiavieira,

This is correct. Images are cached on the Nomad node that runs your docker instance. If another job with the same image occurs on the same node (assuming the container has auth access to the image) it will be able to pull from the local cache rather than re-downloading. This will only ocurr if your job happens to occur on the same node though. If you use a highly used image as your image’s base, like our CircleCI convenience images, there is a high likelkhood that you will find many cached layers as many users are likely to also be using the same layers.

With a completely custom image it is unlikely you will often run into a valid cache for your own image. If you were to build on top of a CircleCI convenience image (If that was a valid option for your use case) you will likely see improvement.

Hey @KyleTryon,

Thank you for the complete explanation.

Unfortunately, I can’t use the CircleCI convenience image as the base image because I need to be an Ubuntu image, not a Debian one. The docs say:

Most CircleCI convenience images are Debian Jessie- or Stretch-based images, however some extend Ubuntu-based images.

But I couldn’t find any ubuntu image. Am I missing something?


Why do you need an ubuntu image?

The convenience images are based on upstream docker images which for now are based on debian. Ubuntu is also debian based, so unless you need ubuntu for a very specific reason any of the convenience images should work just fine for you.

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