324 lines
8.1 KiB
Markdown
324 lines
8.1 KiB
Markdown
# 使用StatefulSet部署有状态应用
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[StatefulSet](../concepts/statefulset.md) 这个对象是专门用来部署用状态应用的，可以为 Pod 提供稳定的身份标识，包括 hostname、启动顺序、DNS 名称等。
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下面以在 kubernetes1.6 版本中部署 zookeeper 和 kafka 为例讲解 StatefulSet 的使用，其中 kafka 依赖于 zookeeper。
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Dockerfile 和配置文件见 [zookeeper](https://github.com/rootsongjc/kubernetes-handbook/tree/master/manifests/zookeeper) 和 [kafka](https://github.com/rootsongjc/kubernetes-handbook/tree/master/manifests/kafka)。
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**注：**所有的镜像基于 CentOS 系统的 JDK 制作，为我的私人镜像，外部无法访问，yaml 中没有配置持久化存储。
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## 部署 Zookeeper
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Dockerfile 中从远程获取 zookeeper 的安装文件，然后在定义了三个脚本：
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- zkGenConfig.sh：生成 zookeeper 配置文件
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- zkMetrics.sh：获取 zookeeper 的 metrics
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- zkOk.sh：用来做 ReadinessProb
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我们在来看下这三个脚本的执行结果。
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zkMetrics.sh 脚本实际上执行的是下面的命令：
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```bash
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$ echo mntr | nc localhost $ZK_CLIENT_PORT >& 1
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zk_version 3.4.6-1569965, built on 02/20/2014 09:09 GMT
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zk_avg_latency 0
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zk_max_latency 5
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zk_min_latency 0
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zk_packets_received 427879
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zk_packets_sent 427890
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zk_num_alive_connections 3
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zk_outstanding_requests 0
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zk_server_state leader
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zk_znode_count 18
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zk_watch_count 3
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zk_ephemerals_count 4
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zk_approximate_data_size 613
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zk_open_file_descriptor_count 29
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zk_max_file_descriptor_count 1048576
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zk_followers 1
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zk_synced_followers 1
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zk_pending_syncs 0
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```
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zkOk.sh 脚本实际上执行的是下面的命令：
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```bash
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$ echo ruok | nc 127.0.0.1 $ZK_CLIENT_PORT
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imok
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```
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**zookeeper.yaml**
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下面是启动三个 zookeeper 实例的 YAML 配置文件：
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```yaml
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---
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apiVersion: v1
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kind: Service
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metadata:
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name: zk-svc
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labels:
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app: zk-svc
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spec:
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ports:
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- port: 2888
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name: server
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- port: 3888
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name: leader-election
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clusterIP: None
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selector:
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app: zk
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---
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apiVersion: v1
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kind: ConfigMap
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metadata:
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name: zk-cm
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data:
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jvm.heap: "1G"
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tick: "2000"
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init: "10"
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sync: "5"
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client.cnxns: "60"
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snap.retain: "3"
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purge.interval: "0"
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---
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apiVersion: policy/v1beta1
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kind: PodDisruptionBudget
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metadata:
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name: zk-pdb
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spec:
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selector:
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matchLabels:
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app: zk
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minAvailable: 2
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---
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apiVersion: apps/v1beta1
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kind: StatefulSet
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metadata:
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name: zk
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spec:
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serviceName: zk-svc
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replicas: 3
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template:
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metadata:
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labels:
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app: zk
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spec:
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affinity:
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podAntiAffinity:
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requiredDuringSchedulingIgnoredDuringExecution:
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- labelSelector:
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matchExpressions:
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- key: "app"
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operator: In
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values:
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- zk
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topologyKey: "kubernetes.io/hostname"
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containers:
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- name: k8szk
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imagePullPolicy: Always
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image: harbor-001.jimmysong.io/library/zookeeper:3.4.6
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resources:
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requests:
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memory: "2Gi"
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cpu: "500m"
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ports:
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- containerPort: 2181
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name: client
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- containerPort: 2888
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name: server
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- containerPort: 3888
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name: leader-election
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env:
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- name : ZK_REPLICAS
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value: "3"
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- name : ZK_HEAP_SIZE
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valueFrom:
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configMapKeyRef:
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name: zk-cm
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key: jvm.heap
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- name : ZK_TICK_TIME
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valueFrom:
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configMapKeyRef:
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name: zk-cm
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key: tick
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- name : ZK_INIT_LIMIT
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valueFrom:
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configMapKeyRef:
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name: zk-cm
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key: init
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- name : ZK_SYNC_LIMIT
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valueFrom:
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configMapKeyRef:
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name: zk-cm
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key: tick
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- name : ZK_MAX_CLIENT_CNXNS
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valueFrom:
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configMapKeyRef:
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name: zk-cm
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key: client.cnxns
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- name: ZK_SNAP_RETAIN_COUNT
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valueFrom:
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configMapKeyRef:
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name: zk-cm
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key: snap.retain
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- name: ZK_PURGE_INTERVAL
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valueFrom:
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configMapKeyRef:
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name: zk-cm
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key: purge.interval
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- name: ZK_CLIENT_PORT
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value: "2181"
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- name: ZK_SERVER_PORT
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value: "2888"
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- name: ZK_ELECTION_PORT
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value: "3888"
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command:
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- sh
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- -c
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- zkGenConfig.sh && zkServer.sh start-foreground
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readinessProbe:
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exec:
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command:
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- "zkOk.sh"
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initialDelaySeconds: 10
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timeoutSeconds: 5
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livenessProbe:
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exec:
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command:
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- "zkOk.sh"
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initialDelaySeconds: 10
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timeoutSeconds: 5
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securityContext:
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runAsUser: 1000
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fsGroup: 1000
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```
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我们再主要下上面那三个脚本的用途。
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## 部署 kafka
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Kafka 的 docker 镜像制作跟 zookeeper 类似，都是从远程下载安装包后，解压安装。
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与 zookeeper 不同的是，只要一个脚本，但是又依赖于我们上一步安装的 zookeeper，kafkaGenConfig.sh 用来生成 kafka 的配置文件。
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我们来看下这个脚本。
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```bash
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#!/bin/bash
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HOST=`hostname -s`
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if [[ $HOST =~ (.*)-([0-9]+)$ ]]; then
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NAME=${BASH_REMATCH[1]}
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ORD=${BASH_REMATCH[2]}
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else
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echo "Failed to extract ordinal from hostname $HOST"
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exit 1
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fi
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MY_ID=$((ORD+1))
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sed -i s"/broker.id=0/broker.id=$MY_ID/g" /opt/kafka/config/server.properties
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sed -i s'/zookeeper.connect=localhost:2181/zookeeper.connect=zk-0.zk-svc.brand.svc:2181,zk-1.zk-svc.brand.svc:2181,zk-2.zk-svc.brand.svc:2181/g' /opt/kafka/config/server.properties
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```
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该脚本根据 statefulset 生成的 pod 的 hostname 的后半截数字部分作为 broker ID，同时再替换 zookeeper 的地址。
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**Kafka.yaml**
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下面是创建 3 个 kafka 实例的 YAML 配置。
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```yaml
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---
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apiVersion: v1
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kind: Service
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metadata:
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name: kafka-svc
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labels:
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app: kafka
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spec:
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ports:
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- port: 9093
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name: server
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clusterIP: None
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selector:
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app: kafka
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---
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apiVersion: policy/v1beta1
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kind: PodDisruptionBudget
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metadata:
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name: kafka-pdb
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spec:
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selector:
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matchLabels:
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app: kafka
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minAvailable: 2
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---
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apiVersion: apps/v1beta1
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kind: StatefulSet
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metadata:
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name: kafka
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spec:
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serviceName: kafka-svc
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replicas: 3
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template:
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metadata:
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labels:
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app: kafka
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spec:
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affinity:
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podAntiAffinity:
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requiredDuringSchedulingIgnoredDuringExecution:
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- labelSelector:
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matchExpressions:
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- key: "app"
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operator: In
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values:
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- kafka
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topologyKey: "kubernetes.io/hostname"
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podAffinity:
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preferredDuringSchedulingIgnoredDuringExecution:
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- weight: 1
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podAffinityTerm:
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labelSelector:
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matchExpressions:
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- key: "app"
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operator: In
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values:
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- zk
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topologyKey: "kubernetes.io/hostname"
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terminationGracePeriodSeconds: 300
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containers:
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- name: k8skafka
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imagePullPolicy: Always
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image: harbor-001.jimmysong.io/library/kafka:2.10-0.8.2.1
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resources:
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requests:
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memory: "1Gi"
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cpu: 500m
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env:
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- name: KF_REPLICAS
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value: "3"
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ports:
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- containerPort: 9093
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name: server
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command:
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- /bin/bash
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- -c
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- "/opt/kafka/bin/kafkaGenConfig.sh && /opt/kafka/bin/kafka-server-start.sh /opt/kafka/config/server.properties"
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env:
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- name: KAFKA_HEAP_OPTS
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value : "-Xmx512M -Xms512M"
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- name: KAFKA_OPTS
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value: "-Dlogging.level=DEBUG"
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readinessProbe:
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tcpSocket:
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port: 9092
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initialDelaySeconds: 15
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timeoutSeconds: 1
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```
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## 参考
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- [StatefulSet - kubernetes.i](https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/)
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