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WARNING: You are looking at unreleased Cilium documentation. Please use the official rendered version released here: http://docs.cilium.io

Installation with managed etcd

The standard k8s_quick_install guide will set up Cilium to use Kubernetes CRDs to store and propagate state between agents. Use of CRDs can impose scale limitations depending on the size of your environment. Use of etcd optimizes the propagation of state between agents. This guide explains the steps required to set up Cilium with a managed etcd where etcd is managed by an operator which maintains an etcd cluster as part of the Kubernetes cluster.

The identity allocation remains to be CRD-based which means that etcd remains an optional component to improve scalability. Failures in providing etcd will not be critical to the availability of Cilium but will reduce the efficacy of state propagation. This allows the managed etcd to recover while depending on Cilium itself to provide connectivity and security.

Should you encounter any issues during the installation, please refer to the troubleshooting_k8s section and / or seek help on the Slack channel.

Deploy Cilium + cilium-etcd-operator

Generate the required YAML file and deploy it:

helm template cilium \
   --namespace kube-system \
   --set global.etcd.enabled=true \
   --set global.etcd.managed=true \
   > cilium.yaml
kubectl create -f cilium.yaml

Validate the Installation

You can monitor as Cilium and all required components are being installed:

kubectl -n kube-system get pods --watch NAME READY STATUS RESTARTS AGE cilium-etcd-operator-6ffbd46df9-pn6cf 1/1 Running 0 7s cilium-operator-cb4578bc5-q52qk 0/1 Pending 0 8s cilium-s8w5m 0/1 PodInitializing 0 7s coredns-86c58d9df4-4g7dd 0/1 ContainerCreating 0 8m57s coredns-86c58d9df4-4l6b2 0/1 ContainerCreating 0 8m57s

It may take a couple of minutes for the etcd-operator to bring up the necessary number of etcd pods to achieve quorum. Once it reaches quorum, all components should be healthy and ready:

cilium-etcd-8d95ggpjmw 1/1 Running 0 78s cilium-etcd-operator-6ffbd46df9-pn6cf 1/1 Running 0 4m12s cilium-etcd-t695lgxf4x 1/1 Running 0 118s cilium-etcd-zw285m6t9g 1/1 Running 0 2m41s cilium-operator-cb4578bc5-q52qk 1/1 Running 0 4m13s cilium-s8w5m 1/1 Running 0 4m12s coredns-86c58d9df4-4g7dd 1/1 Running 0 13m coredns-86c58d9df4-4l6b2 1/1 Running 0 13m etcd-operator-5cf67779fd-hd9j7 1/1 Running 0 2m42s

Troubleshooting

  • Make sure that kube-dns or coredns is running and healthy in the kube-system namespace. A functioning Kubernetes DNS is strictly required in order for Cilium to resolve the ClusterIP of the etcd cluster. If either kube-dns or coredns were already running before Cilium was deployed, the pods may be managed by a former CNI plugin. cilium-operator will automatically restart the pods to ensure that they are being managed by the Cilium CNI plugin. You can manually restart the pods as well if required and validate that Cilium is managing kube-dns or coredns by running:

    kubectl -n kube-system get cep

    You should see kube-dns-xxx or coredns-xxx pods.

  • In order for the entire system to come up, the following components have to be running at the same time:

    • kube-dns or coredns
    • cilium-xxx
    • cilium-etcd-operator
    • etcd-operator
    • etcd-xxx

    All timeouts are configured that this will typically work out smoothly even if some of the pods restart once or twice. In case any of the above pods get into a long CrashLoopBackoff, bootstrapping can be expedited by restarting the pods to reset the CrashLoopBackoff time.

CoreDNS: Enable reverse lookups

In order for the TLS certificates between etcd peers to work correctly, a DNS reverse lookup on a pod IP must map back to pod name. If you are using CoreDNS, check the CoreDNS ConfigMap and validate that in-addr.arpa and ip6.arpa are listed as wildcards for the kubernetes block like this:

kubectl -n kube-system edit cm coredns
[...]
apiVersion: v1
data:
  Corefile: |
    .:53 {
        errors
        health
        kubernetes cluster.local in-addr.arpa ip6.arpa {
          pods insecure
          upstream
          fallthrough in-addr.arpa ip6.arpa
        }
        prometheus :9153
        proxy . /etc/resolv.conf
        cache 30
    }

The contents can look different than the above. The specific configuration that matters is to make sure that in-addr.arpa and ip6.arpa are listed as wildcards next to cluster.local.

You can validate this by looking up a pod IP with the host utility from any pod:

host 10.60.20.86
86.20.60.10.in-addr.arpa domain name pointer cilium-etcd-972nprv9dp.cilium-etcd.kube-system.svc.cluster.local.

What is the cilium-etcd-operator?

The cilium-etcd-operator uses and extends the etcd-operator to guarantee quorum, auto-create certificates, and manage compaction:

  • Automatic re-creation of the etcd cluster when the cluster loses quorum. The standard etcd-operator will refuse to bring up new etcd nodes and the etcd cluster becomes unusable.
  • Automatic creation of certificates and keys. This simplifies the installation of the operator and makes the certificates and keys required to access the etcd cluster available to Cilium using a well known Kubernetes secret name.
  • Compaction is automatically handled.

Limitations

Use of the cilium-etcd-operator offers a lot of advantages including simplicity of installation, automatic management of the etcd cluster including compaction, restart on quorum loss, and automatic use of TLS. There are several disadvantages which can become of relevance as you scale up your clusters:

  • etcd nodes operated by the etcd-operator will not use persistent storage. Once the etcd cluster looses quorum, the etcd cluster is automatically re-created by the cilium-etcd-operator. Cilium will automatically recover and re-create all state in etcd. This operation can take can couple of seconds and may cause minor disruptions as ongoing distributed locks are invalidated and security identities have to be re-allocated.
  • etcd is very sensitive to disk IO latency and requires fast disk access at a certain scale. The cilium-etcd-operator will not take any measures to provide fast disk access and performance will depend whatever is provided to the pods in your Kubernetes cluster. See etcd Hardware recommendations for more details.