使用StatefulSet部署有状态应用

部署Zookeeper
- zookeeper.yaml
部署kafka
- Kafka.yaml

StatefulSet 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

下面以在 kubernetes 中部署 zookeeper 和 kafka 为例讲解StatefulSet的使用，其中kafka依赖于zookeeper

部署Zookeeper

Dockerfile中从远程获取zookeeper的安装文件，然后在定义了三个脚本：

zkGenConfig.sh ：生成zookeeper配置文件
zkMetrics.sh ：获取zookeeper的metrics
zkOk.sh ：用来做ReadinessProb

zkMetrics.sh脚本实际上执行的是下面的命令：

$ echo mntr | nc localhost $ZK_CLIENT_PORT >& 1
zk_version    3.4.6-1569965, built on 02/20/2014 09:09 GMT
zk_avg_latency    0
zk_max_latency    5
zk_min_latency    0
zk_packets_received    427879
zk_packets_sent    427890
zk_num_alive_connections    3
zk_outstanding_requests    0
zk_server_state    leader
zk_znode_count    18
zk_watch_count    3
zk_ephemerals_count    4
zk_approximate_data_size    613
zk_open_file_descriptor_count    29
zk_max_file_descriptor_count    1048576
zk_followers    1
zk_synced_followers    1
zk_pending_syncs    0

zkOk.sh脚本实际上执行的是下面的命令：

$ echo ruok | nc 127.0.0.1 $ZK_CLIENT_PORT
imok

zookeeper.yaml

下面是启动三个zookeeper实例的yaml配置文件：

---
apiVersion: v1
kind: Service
metadata:
  name: zk-svc
  labels:
    app: zk-svc
spec:
  ports:
  - port: 2888
    name: server
  - port: 3888
    name: leader-election
  clusterIP: None
  selector:
    app: zk
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: zk-cm
data:
  jvm.heap: "1G"
  tick: "2000"
  init: "10"
  sync: "5"
  client.cnxns: "60"
  snap.retain: "3"
  purge.interval: "0"
---
apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
  name: zk-pdb
spec:
  selector:
    matchLabels:
      app: zk
  minAvailable: 2
---
apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
  name: zk
spec:
  serviceName: zk-svc
  replicas: 3
  template:
    metadata:
      labels:
	app: zk
    spec:
      affinity:
	podAntiAffinity:
	  requiredDuringSchedulingIgnoredDuringExecution:
	    - labelSelector:
		matchExpressions:
		  - key: "app"
		    operator: In
		    values:
		    - zk
	      topologyKey: "kubernetes.io/hostname"
      containers:
      - name: k8szk
	imagePullPolicy: Always
	image: harbor-001.jimmysong.io/library/zookeeper:3.4.6
	resources:
	  requests:
	    memory: "2Gi"
	    cpu: "500m"
	ports:
	- containerPort: 2181
	  name: client
	- containerPort: 2888
	  name: server
	- containerPort: 3888
	  name: leader-election
	env:
	- name : ZK_REPLICAS
	  value: "3"
	- name : ZK_HEAP_SIZE
	  valueFrom:
	    configMapKeyRef:
		name: zk-cm
		key: jvm.heap
	- name : ZK_TICK_TIME
	  valueFrom:
	    configMapKeyRef:
		name: zk-cm
		key: tick
	- name : ZK_INIT_LIMIT
	  valueFrom:
	    configMapKeyRef:
		name: zk-cm
		key: init
	- name : ZK_SYNC_LIMIT
	  valueFrom:
	    configMapKeyRef:
		name: zk-cm
		key: tick
	- name : ZK_MAX_CLIENT_CNXNS
	  valueFrom:
	    configMapKeyRef:
		name: zk-cm
		key: client.cnxns
	- name: ZK_SNAP_RETAIN_COUNT
	  valueFrom:
	    configMapKeyRef:
		name: zk-cm
		key: snap.retain
	- name: ZK_PURGE_INTERVAL
	  valueFrom:
	    configMapKeyRef:
		name: zk-cm
		key: purge.interval
	- name: ZK_CLIENT_PORT
	  value: "2181"
	- name: ZK_SERVER_PORT
	  value: "2888"
	- name: ZK_ELECTION_PORT
	  value: "3888"
	command:
	- sh
	- -c
	- zkGenConfig.sh && zkServer.sh start-foreground
	readinessProbe:
	  exec:
	    command:
	    - "zkOk.sh"
	  initialDelaySeconds: 10
	  timeoutSeconds: 5
	livenessProbe:
	  exec:
	    command:
	    - "zkOk.sh"
	  initialDelaySeconds: 10
	  timeoutSeconds: 5
      securityContext:
	runAsUser: 1000
	fsGroup: 1000

部署kafka

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

与zookeeper不同的是，只要一个脚本，但是又依赖于上一步安装的zookeeper， kafkaGenConfig.sh 用来生成kafka的配置文件：

#!/bin/bash
HOST=`hostname -s`
if [[ $HOST =~ (.*)-([0-9]+)$ ]]; then
        NAME=${BASH_REMATCH[1]}
        ORD=${BASH_REMATCH[2]}
else
        echo "Failed to extract ordinal from hostname $HOST"
        exit 1
fi

MY_ID=$((ORD+1))
sed -i s"/broker.id=0/broker.id=$MY_ID/g" /opt/kafka/config/server.properties
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

根据statefulset生成的pod的hostname的后半截数字部分作为broker ID
再替换zookeeper的地址

Kafka.yaml

创建3个kafka实例的yaml配置：

---
apiVersion: v1
kind: Service
metadata:
  name: kafka-svc
  labels:
    app: kafka
spec:
  ports:
  - port: 9093
    name: server
  clusterIP: None
  selector:
    app: kafka
---
apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
  name: kafka-pdb
spec:
  selector:
    matchLabels:
      app: kafka
  minAvailable: 2
---
apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
  name: kafka
spec:
  serviceName: kafka-svc
  replicas: 3
  template:
    metadata:
      labels:
	app: kafka
    spec:
      affinity:
	podAntiAffinity:
	  requiredDuringSchedulingIgnoredDuringExecution:
	    - labelSelector:
		matchExpressions:
		  - key: "app"
		    operator: In
		    values:
		    - kafka
	      topologyKey: "kubernetes.io/hostname"
	podAffinity:
	  preferredDuringSchedulingIgnoredDuringExecution:
	     - weight: 1
	       podAffinityTerm:
		 labelSelector:
		    matchExpressions:
		      - key: "app"
			operator: In
			values:
			- zk
		 topologyKey: "kubernetes.io/hostname"
      terminationGracePeriodSeconds: 300
      containers:
      - name: k8skafka
	imagePullPolicy: Always
	image: harbor-001.jimmysong.io/library/kafka:2.10-0.8.2.1
	resources:
	  requests:
	    memory: "1Gi"
	    cpu: 500m
	env:
	- name: KF_REPLICAS
	  value: "3"
	ports:
	- containerPort: 9093
	  name: server
	command:
	- /bin/bash
	- -c
	- "/opt/kafka/bin/kafkaGenConfig.sh && /opt/kafka/bin/kafka-server-start.sh /opt/kafka/config/server.properties"
	env:
	- name: KAFKA_HEAP_OPTS
	  value : "-Xmx512M -Xms512M"
	- name: KAFKA_OPTS
	  value: "-Dlogging.level=DEBUG"
	readinessProbe:
	   tcpSocket:
	     port: 9092
	   initialDelaySeconds: 15
	   timeoutSeconds: 1

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使用StatefulSet部署有状态应用

Table of Contents

部署Zookeeper

zookeeper.yaml

部署kafka

Kafka.yaml