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Clean up 2023-09-25-kubeadm-use-etcd-learner-mode

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windsonsea 2023-09-25 10:19:06 +08:00
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content/en/blog/_posts/2023-09-25-kubeadm-use-etcd-learner-mode.md
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@ -9,7 +9,7 @@ slug: kubeadm-use-etcd-learner-mode
The [`kubeadm`](/docs/reference/setup-tools/kubeadm/) tool now supports etcd learner mode, which
allows you to enhance the resilience and stability
of your Kubernetes clusters by leveraging the [learner mode](https://etcd.io/docs/v3.4/learning/design-learner/#appendix-learner-implementation-in-v34)
of your Kubernetes clusters by leveraging the [learner mode](https://etcd.io/docs/v3.4/learning/design-learner/#appendix-learner-implementation-in-v34)
feature introduced in etcd version 3.4.
This guide will walk you through using etcd learner mode with kubeadm. By default, kubeadm runs
a local etcd instance on each control plane node.
@ -23,19 +23,19 @@ promoted to a voting member only after the etcd data are fully aligned.
etcd learner mode offers several compelling reasons to consider its adoption
in Kubernetes clusters:
1. **Enhanced Resilience**: etcd learner nodes are non-voting members that catch up with
the leader's logs before becoming fully operational. This prevents new cluster members
from disrupting the quorum or causing leader elections, making the cluster more resilient
during membership changes.
2. **Reduced Cluster Unavailability**: Traditional approaches to adding new members often
result in cluster unavailability periods, especially in slow infrastructure or misconfigurations.
etcd learner mode minimizes such disruptions.
3. **Simplified Maintenance**: Learner nodes provide a safer and reversible way to add or replace
cluster members. This reduces the risk of accidental cluster outages due to misconfigurations or
missteps during member additions.
4. **Improved Network Tolerance**: In scenarios involving network partitions, learner mode allows
for more graceful handling. Depending on the partition a new member lands, it can seamlessly
integrate with the existing cluster without causing disruptions.
1. **Enhanced Resilience**: etcd learner nodes are non-voting members that catch up with
the leader's logs before becoming fully operational. This prevents new cluster members
from disrupting the quorum or causing leader elections, making the cluster more resilient
during membership changes.
1. **Reduced Cluster Unavailability**: Traditional approaches to adding new members often
result in cluster unavailability periods, especially in slow infrastructure or misconfigurations.
etcd learner mode minimizes such disruptions.
1. **Simplified Maintenance**: Learner nodes provide a safer and reversible way to add or replace
cluster members. This reduces the risk of accidental cluster outages due to misconfigurations or
missteps during member additions.
1. **Improved Network Tolerance**: In scenarios involving network partitions, learner mode allows
for more graceful handling. Depending on the partition a new member lands, it can seamlessly
integrate with the existing cluster without causing disruptions.
In summary, the etcd learner mode improves the reliability and manageability of Kubernetes clusters
during member additions and changes, making it a valuable feature for cluster operators.
@ -80,7 +80,7 @@ ETCDCTL_API=3 etcdctl --endpoints 127.0.0.1:2379 \
--cert=/etc/kubernetes/pki/etcd/server.crt \
--key=/etc/kubernetes/pki/etcd/server.key \
--cacert=/etc/kubernetes/pki/etcd/ca.crt \
member list
member list
...
dc543c4d307fadb9, started, node1, https://10.6.177.40:2380, https://10.6.177.40:2379, false
```
@ -88,20 +88,24 @@ dc543c4d307fadb9, started, node1, https://10.6.177.40:2380, https://10.6.177.40:
To check if the Kubernetes control plane is healthy, run `kubectl get node -l node-role.kubernetes.io/control-plane=`
and check if the nodes are ready.
Note: It is recommended to have an odd number of members in a etcd cluster.
{{< note >}}
It is recommended to have an odd number of members in an etcd cluster.
{{< /note >}}
Before joining a worker node to the new Kubernetes cluster, ensure that the control plane nodes are healthy.
## What's next
- The feature gate `EtcdLearnerMode` is alpha in v1.27 and we expect it to graduate to beta in the next
minor release of Kubernetes (v1.29).
- etcd has an open issue that may make the process more automatic:
minor release of Kubernetes (v1.29).
- etcd has an open issue that may make the process more automatic:
[Support auto-promoting a learner member to a voting member](https://github.com/etcd-io/etcd/issues/15107).
- Learn more about the kubeadm [configuration format](/docs/reference/config-api/kubeadm-config.v1beta3/) here.
- Learn more about the kubeadm [configuration format](/docs/reference/config-api/kubeadm-config.v1beta3/).
## Feedback
Was this guide helpful? If you have any feedback or encounter any issues, please let us know.
Your feedback is always welcome! Join the bi-weekly [SIG Cluster Lifecycle meeting](https://docs.google.com/document/d/1Gmc7LyCIL_148a9Tft7pdhdee0NBHdOfHS1SAF0duI4/edit)
or weekly [kubeadm office hours](https://docs.google.com/document/d/130_kiXjG7graFNSnIAgtMS1G8zPDwpkshgfRYS0nggo/edit). Or reach us via [Slack](https://slack.k8s.io/) (channel **#kubeadm**), or the [SIG's mailing list](https://groups.google.com/g/kubernetes-sig-cluster-lifecycle).
or weekly [kubeadm office hours](https://docs.google.com/document/d/130_kiXjG7graFNSnIAgtMS1G8zPDwpkshgfRYS0nggo/edit).
Or reach us via [Slack](https://slack.k8s.io/) (channel **#kubeadm**), or the
[SIG's mailing list](https://groups.google.com/g/kubernetes-sig-cluster-lifecycle).