Configuring Pull Through Cache

In this guide we will create a set of local caching Docker registry proxies to minimize local cluster startup time.

When running Talos locally, pulling images from Docker registries might take a significant amount of time. We spin up local caching pass-through registries to cache images and configure a local Talos cluster to use those proxies. A similar approach might be used to run Talos in production in air-gapped environments. It can be also used to verify that all the images are available in local registries.

Video Walkthrough

To see a live demo of this writeup, see the video below:

Requirements

The follow are requirements for creating the set of caching proxies:

  • Docker 18.03 or greater
  • Local cluster requirements for either docker or fireracker.

Launch the Caching Docker Registry Proxies

Talos pulls from docker.io, k8s.gcr.io, gcr.io and quay.io by default. If your configuration is different, you might need to modify the commands below:

docker run -d -p 5000:5000 \
    -e REGISTRY_PROXY_REMOTEURL=https://registry-1.docker.io \
    --restart always \
    --name registry-docker.io registry:2

docker run -d -p 5001:5000 \
    -e REGISTRY_PROXY_REMOTEURL=https://k8s.gcr.io \
    --restart always \
    --name registry-k8s.gcr.io registry:2

docker run -d -p 5002:5000 \
    -e REGISTRY_PROXY_REMOTEURL=https://quay.io \
    --restart always \
    --name registry-quay.io registry:2.5

docker run -d -p 5003:5000 \
    -e REGISTRY_PROXY_REMOTEURL=https://gcr.io \
    --restart always \
    --name registry-gcr.io registry:2

Note: Proxies are started as docker containers, and they're automatically configured to start with Docker daemon. Please note that quay.io proxy doesn't support recent Docker image schema, so we run older registry image version (2.5).

As a registry container can only handle a single upstream Docker registry, we launch a container per upstream, each on its own host port (5000, 5001, 5002).

Using Caching Registries with firecracker Local Cluster

With a firecracker local cluster, a bridge interface is created on the host. As registry containers expose their ports on the host, we can use bridge IP to direct proxy requests.

sudo talosctl cluster create --provisioner firecracker \
    --registry-mirror docker.io=http://10.5.0.1:5000 \
    --registry-mirror k8s.gcr.io=http://10.5.0.1:5001 \
    --registry-mirror quay.io=http://10.5.0.1:5002 \
    --registry-mirror gcr.io=http://10.5.0.1:5003

The Talos local cluster should now start pulling via caching registries. This can be verified via registry logs, e.g. docker logs -f registry-docker.io. The first time cluster boots, images are pulled and cached, so next cluster boot should be much faster.

Note: 10.5.0.1 is a bridge IP with default network (10.5.0.0/24), if using custom --cidr, value should be adjusted accordingly.

Using Caching Registries with docker Local Cluster

With a docker local cluster we can use docker bridge IP, default value for that IP is 172.17.0.1. On Linux, the docker bridge address can be inspected with ip addr show docker0.

talosctl cluster create --provisioner docker \
    --registry-mirror docker.io=http://172.17.0.1:5000 \
    --registry-mirror k8s.gcr.io=http://172.17.0.1:5001 \
    --registry-mirror quay.io=http://172.17.0.1:5002 \
    --registry-mirror gcr.io=http://172.17.0.1:5003

Cleaning Up

To cleanup, run:

docker rm -f registry-docker.io
docker rm -f registry-k8s.gcr.io
docker rm -f registry-quay.io
docker rm -f registry-gcr.io

Note: Removing docker registry containers also removes the image cache. So if you plan to use caching registries, keep the containers running.