前言

整个k8s诸多组件几乎都是无状态的，所有的数据保存在etcd里，可以说etcd是整个k8s集群的数据库。可想而知，etcd的重要性。因而做好etcd数据备份工作至关重要。这篇主要讲一下我司的相关的实践。

备份etcd数据到s3

能做etcd的备份方案很多，但是大同小异，基本上都是利用了etcdctl命令来完成。

为什么选择s3那？

• 因为我们单位对于aws使用比较多，另外我们希望我们备份到一个高可用的存储中，而不是部署etcd的本机中。
• 此外，s3支持存储的生命周期的设置。设置一下，就可以aws帮助我们定时删除旧数据，保留新的备份数据。

具体方案

我们基本上用了etcd-backup这个项目，当然也fork了，做了稍微的更改，主要是更改了dockerfile。将etcdctl 修改为我们线上实际的版本。

修改之后的dockerfile如下：

FROM alpine:3.8

RUN apk add --no-cache curl

# Get etcdctl
ENV ETCD_VER=v3.2.24
RUN \
  cd /tmp && \
  curl -L https://storage.googleapis.com/etcd/${ETCD_VER}/etcd-${ETCD_VER}-linux-amd64.tar.gz | \
  tar xz -C /usr/local/bin --strip-components=1

COPY ./etcd-backup /
ENTRYPOINT ["/etcd-backup"]
CMD ["-h"]

之后就是docker build之类了。

k8s部署方案

选择k8s中的cronjob比较合适，我的备份策略是每三小时备份一次。

cronjob.yaml:

apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: etcd-backup
  namespace: kube-system
spec:
  schedule: "0 */4 * * *"
  successfulJobsHistoryLimit: 2
  failedJobsHistoryLimit: 2
  jobTemplate:
    spec:
      # Job timeout
      activeDeadlineSeconds: 300
      template:
        spec:
          tolerations:
          # Tolerate master taint
          - key: node-role.kubernetes.io/master
            operator: Exists
            effect: NoSchedule
          # Container creates etcd backups.
          # Run container in host network mode on G8s masters
          # to be able to use 127.0.0.1 as etcd address.
          # For etcd v2 backups container should have access
          # to etcd data directory. To achive that,
          # mount /var/lib/etcd3 as a volume.
          nodeSelector:
            node-role.kubernetes.io/master: ""
          containers:
          - name: etcd-backup
            image: iyacontrol/etcd-backup:0.1
            args:
            # backup guest clusters only on production instalations
            # testing installation can have many broken guest clusters
            - -prefix=k8s-prod-1
            - -etcd-v2-datadir=/var/lib/etcd
            - -etcd-v3-endpoints=https://172.xx.xx.221:2379,https://172.xx.xx.83:2379,https://172.xx.xx.246:2379
            - -etcd-v3-cacert=/certs/ca.crt
            - -etcd-v3-cert=/certs/server.crt
            - -etcd-v3-key=/certs/server.key
            - -aws-s3-bucket=mybucket
            - -aws-s3-region=us-east-1
            volumeMounts:
            - mountPath: /var/lib/etcd
              name: etcd-datadir
            - mountPath: /certs
              name: etcd-certs
            env:
              - name: ETCDBACKUP_AWS_ACCESS_KEY
                valueFrom:
                  secretKeyRef:
                    name: etcd-backup
                    key: ETCDBACKUP_AWS_ACCESS_KEY
              - name: ETCDBACKUP_AWS_SECRET_KEY
                valueFrom:
                  secretKeyRef:
                    name: etcd-backup
                    key: ETCDBACKUP_AWS_SECRET_KEY
              - name: ETCDBACKUP_PASSPHRASE
                valueFrom:
                  secretKeyRef:
                    name: etcd-backup
                    key: ETCDBACKUP_PASSPHRASE
          volumes:
          - name: etcd-datadir
            hostPath:
              path: /var/lib/etcd
          - name: etcd-certs
            hostPath:
              path: /etc/kubernetes/pki/etcd/
          # Do not restart pod, job takes care on restarting failed pod.
          restartPolicy: Never
          hostNetwork: true
   

注意：容忍 和 nodeselector配合，让pod调度到master节点上。

然后secret.yaml:

apiVersion: v1
kind: Secret
metadata:
  name: etcd-backup
  namespace: kube-system
type: Opaque
data:
  ETCDBACKUP_AWS_ACCESS_KEY: QUtJTI0TktCT0xQRlEK
  ETCDBACKUP_AWS_SECRET_KEY: aXJ6eThjQnM2MVRaSkdGMGxDeHhoeFZNUDU4ZGRNbgo=
  ETCDBACKUP_PASSPHRASE: ""

总结

之前我们尝试过，etcd-operator来完成backup。实际使用过程中，发现并不好，概念很多，组件复杂，代码很多写法太死。

最后选择etcd-backup。主要是因为简单，less is more。看源码，用golang编写，扩展自己的一些需求，也比较简单。