有状态部署StatefulSet控制器

1.StatefulSet概述

部署有状态应用
解决Pod独立生命周期，保持Pod启动顺序和唯一性

1. 稳定，唯一的网络标识符，持久存储

2. 有序，优雅的部署和扩展、删除和终止

3. 有序，滚动更新

应用场景：数据库

StatefulSet与Deployment区别：

有身份的！

身份三要素：

域名
主机名
存储（PVC）

无状态的适用：web，api，微服务的部署，可以运行在任意节点，不依赖后端持久化存储。

有状态的适用：需要有固定ip，pod有各自的存储，可以按一定规则进行扩缩容。

2.正常service和headlessService对比

normal sevice:

通过一个cluster-ip 10.0.0.224:80 来反向代理 endpoints

10.244.0.58:8080 10.244.1.78:8080 10.244.1.88:8080

headless service:

无头服务，需要将 clusterIP: None 并且不能设置nodePort

web-headlessService.yaml

apiVersion: v1
kind: Service metadata:  labels:  app: web  name: headless-svc  namespace: default spec:  clusterIP: None  ports:  - port: 80  protocol: TCP  targetPort: 8080  selector:  app: web

statefulSet.yaml seviceName关联上面的svc headless-svc

apiVersion: apps/v1
kind: StatefulSet metadata:  name: web spec:  selector:  matchLabels:  app: nginx  serviceName: "headless-svc"  replicas: 3  template:  metadata:  labels:  app: nginx  spec:  terminationGracePeriodSeconds: 10  containers:  - name: nginx  image: nginx  ports:  - containerPort: 80  name: web

statefulSet生成的pod 都会有个稳定有序的标识符 statefulSetName-index 如 web-0

service域名解析差异

normal service 解析的是 service 的clusterIP

由于headless service 的clusterIP 设置的None 所以解析 service name 的时候解析是sevice 对应的pod ip

ClusterIP A记录格式：(normal service)

<service-name>.<namespace-name>.svc.cluster.local

ClusterIP=None A记录格式：(headless servcie)

<statefulsetName-index>.<service-name>.<namespace-name>.svc.cluster.local

示例：web-0.nginx.default.svc.cluster.local

相比 normal service 的域名格式 headless service 解析出来的格式多一个< statefulSetName-index >

statefulSet 管理的pod 他主机名 statefulSetName-index

3.StatefulSet 存储

StatefulSet使用 volumeClaimTemplates创建每个Pod的PersistentVolume的同时会为每个pod分配并创建一个带编号的pvc

使用无状态部署创建的动态供给pv 和pvc 是没有编号的

statfulset的删除机制

执行kubectl delete -f statefulSet.yaml

按照创建的先后进行删除，先创建的将会被先删除。

statefulset的启动机制

有序的 pv ，pvc创建

这样就可以使得对应的pod 申请到的 pv 和pvc 与之向对应。

各个pod之前的存储是互相独立的不共享

在web-0创建的文件在 web-1中是看不到的

4.statefulSet应用示例（Mysql集群）

创建个statefulSet应用目录

mkdir  statefulset-mysqlCluster

创建configMap

configmap.yaml 主要保存主从配置

apiVersion: v1
kind: ConfigMap metadata:  name: mysql  labels:  app: mysql data:  master.cnf: |  # Apply this config only on the master.  [client]  default-character-set=utf8mb4   [mysql]  default-character-set=utf8mb4   [mysqld]  # 打开binlog日志  log-bin  binlog_expire_logs_seconds=2592000  max_connections=10000  # 在容器里面需要设置下时区  default-time-zone='+8:00'  character-set-client-handshake=FALSE  character-set-server=utf8mb4  collation-server=utf8mb4_unicode_ci  init_connect='SET NAMES utf8mb4 COLLATE utf8mb4_unicode_ci'  slave.cnf: |  # Apply this config only on slaves.  [client]  default-character-set=utf8mb4   [mysql]  default-character-set=utf8mb4   [mysqld]  # 机器设置只读  super-read-only  max_connections=10000  default-time-zone='+8:00'  character-set-client-handshake=FALSE  character-set-server=utf8mb4  collation-server=utf8mb4_unicode_ci  init_connect='SET NAMES utf8mb4 COLLATE utf8mb4_unicode_ci'

创建service

service.yaml

apiVersion: v1
kind: Service metadata:  name: mysql-svc-master  labels:  app: mysql spec:  selector:  app: mysql  ports:  - port: 3306  name: mysql  clusterIP: None

需要先创建一个Headless Service，用于从机去访问主机。从机可以通过<pod-name>.mysql-svc-master去访问到指定的pod。

创建statefulSet

apiVersion: apps/v1
kind: StatefulSet metadata:  name: mysql-ss spec:  selector:  matchLabels:  app: mysql # 匹配 .spec.template.metadata.labels  serviceName: mysql-svc-master  replicas: 3  template:  metadata:  labels:  app: mysql # 匹配 .spec.selector.matchLabels  spec:  imagePullSecrets:  - name: myregistry  initContainers:  - name: init-mysql  image: registry.cn-hangzhou.aliyuncs.com/benjamin-learn/mysql:8.0  command:  - bash  - "-c"  - |  set ex  # Generate mysql server-id from pod ordinal index.  [[ `hostname` =~ -([0-9]+)$ ]] || exit 1  ordinal=${BASH_REMATCH[1]}  echo [mysqld] > /mnt/conf.d/server-id.cnf   # Add an offset to avoid reserved server-id=0 value.  echo server-id=$((100 + $ordinal)) >> /mnt/conf.d/server-id.cnf   # Copy appropriate conf.d files from config-map to emptyDir.  if [[ $ordinal -eq 0 ]]; then  cp /mnt/config-map/master.cnf /mnt/conf.d/  else  cp /mnt/config-map/slave.cnf /mnt/conf.d/  fi  volumeMounts:  - name: conf  mountPath: /mnt/conf.d  - name: config-map  mountPath: /mnt/config-map  - name: clone-mysql  image: registry.cn-hangzhou.aliyuncs.com/benjamin-learn/xtrabackup:1.0  command:  - bash  - "-c"  - |  set -ex  # Skip the clone if data already exists.  [[ -d /var/lib/mysql/mysql ]] && exit 0   # Skip the clone on master (ordinal index 0).  [[ `hostname` =~ -([0-9]+)$ ]] || exit 1  ordinal=${BASH_REMATCH[1]}  [[ $ordinal -eq 0 ]] && exit 0   # Clone data from previous peer.  ncat --recv-only mysql-ss-$(($ordinal-1)).mysql-svc-master 3307 | xbstream -x -C /var/lib/mysql  # Prepare the backup.  xtrabackup --prepare --target-dir=/var/lib/mysql  volumeMounts:  - name: data  mountPath: /var/lib/mysql  subPath: mysql  - name: conf  mountPath: /etc/mysql/conf.d  containers:  - name: mysql  image: mysql:8.0  args: ["--default-authentication-plugin=mysql_native_password"]  env:  - name: MYSQL_ALLOW_EMPTY_PASSWORD  value: "1"  ports:  - name: mysql  containerPort: 3306  volumeMounts:  - name: data  mountPath: /var/lib/mysql  subPath: mysql  - name: conf  mountPath: /etc/mysql/conf.d  resources:  requests:  cpu: 250m  memory: 256Mi  limits:  cpu: 500m  memory: 512Mi  livenessProbe:  exec:  command: ["mysqladmin", "ping"]  initialDelaySeconds: 30  periodSeconds: 10  timeoutSeconds: 5  readinessProbe:  exec: # Check we can execute queries over TCP (skip-networking is off).  command: ["mysql", "-h", "127.0.0.1", "-e", "SELECT 1"]  initialDelaySeconds: 5  periodSeconds: 2  timeoutSeconds: 1  - name: xtrabackup  image: mzmuer/xtrabackup:1.0  ports:  - name: xtrabackup  containerPort: 3307  command:  - bash  - "-c"  - |  set -ex  cd /var/lib/mysql # Determine binlog position of cloned data, if any.  if [[ -s xtrabackup_slave_info ]]; then # XtraBackup already generated a partial "CHANGE MASTER TO" query # because we're cloning from an existing slave.  mv xtrabackup_slave_info change_master_to.sql.in # Ignore xtrabackup_binlog_info in this case (it's useless).  rm -f xtrabackup_binlog_info  elif [[ -f xtrabackup_binlog_info ]]; then # We're cloning directly from master. Parse binlog position. [[ `cat xtrabackup_binlog_info` =~ ^(.*?)[[:space:]]+(.*?)$ ]] || exit 1  rm xtrabackup_binlog_info  echo "CHANGE MASTER TO MASTER_LOG_FILE='${BASH_REMATCH[1]}',\  MASTER_LOG_POS=${BASH_REMATCH[2]}" > change_master_to.sql.in  fi # Check if we need to complete a clone by starting replication.  if [[ -f change_master_to.sql.in ]]; then  echo "Waiting for mysqld to be ready (accepting connections)"  until mysql -h 127.0.0.1 -e "SELECT 1"; do sleep 1; done  echo "Initializing replication from clone position" # In case of container restart, attempt this at-most-once.  mv change_master_to.sql.in change_master_to.sql.orig  mysql -h 127.0.0.1 <<EOF  $(<change_master_to.sql.orig),  MASTER_HOST='mysql-ss-0.mysql-svc-master',  MASTER_USER='root',  MASTER_PASSWORD='',  MASTER_CONNECT_RETRY=10;  START SLAVE;  EOF  fi # Start a server to send backups when requested by peers.  exec ncat --listen --keep-open --send-only --max-conns=1 3307 -c \ "xtrabackup --backup --slave-info --stream=xbstream --host=127.0.0.1 --user=root"  volumeMounts:  - name: data  mountPath: /var/lib/mysql  subPath: mysql  - name: conf  mountPath: /etc/mysql/conf.d  resources:  requests:  cpu: 100m  memory: 100Mi  limits:  cpu: 200m  memory: 200Mi  volumes:  - name: conf  emptyDir: {}  - name: config-map  configMap:  name: mysql  volumeClaimTemplates:  - metadata:  name: data  spec: # 这里需要注意下，要修改为自己的StorageClass的名称  storageClassName: managed-nfs-storage  accessModes:  - ReadWriteOnce  resources:  requests:  storage: 10Gi

init-mysql
初始化配置文件和server-id文件，分别给主机和从机不同的配置文件。
clone-mysql
初始化mysql。如果是从机需要先用xtrabackup做一次全量的备份，备份的数据来自于前一个pod。
mysql
按照配置启动mysql
xtrabackup
执行命令启动slave，并利用ncat启动监听，如果扩展新的节点，传输数据到新节点。

验证集群数据同步

进入主库创建个db名称test