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参考链接：
apiVersion: v1kind: ConfigMapmetadata: name: mysql labels: app: mysqldata: master.cnf: | # Apply this config only on the master. [mysqld] log-bin slave.cnf: | # Apply this config only on slaves. [mysqld] super-read-only
在pod初始化时, pod会根据自身标识(master或slave)从configmap中应用指定配置. 被应用配置将覆盖my.cnf中的配置. 目的是使master向slave提供复制日志服务，并设置slave拒绝非复制写入.
# Headless service for stable DNS entries of StatefulSet members.apiVersion: v1kind: Servicemetadata: name: mysql labels: app: mysqlspec: ports: - name: mysql port: 3306 clusterIP: None selector: app: mysql
apiVersion: apps/v1beta1apiVersion: apps/v1kind: StatefulSetmetadata: name: mysqlspec: selector: matchLabels: app: mysql serviceName: mysql replicas: 3 template: metadata: labels: app: mysql spec: initContainers: - name: init-mysql image: mysql:5.7 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 [[ $ordinal -eq 0 ]]; then cp /mnt/config-map/master.cnf /mnt/conf.d/ else cp /mnt/config-map/slave.cnf /mnt/conf.d/ fi volumeMounts: - name: conf mountPath: /mnt/conf.d - name: config-map mountPath: /mnt/config-map - name: clone-mysql image: gcr.io/google-samples/xtrabackup:1.0 command: - bash - "-c" - | set -ex # Skip the clone if data already exists. [[ -d /var/lib/mysql/mysql ]] && exit 0 # Skip the clone on master (ordinal index 0). [[ `hostname` =~ -([0-9]+)$ ]] || exit 1 ordinal=${BASH_REMATCH[1]} [[ $ordinal -eq 0 ]] && exit 0 # Clone data from previous peer. ncat --recv-only mysql-$(($ordinal-1)).mysql 3307 | xbstream -x -C /var/lib/mysql # Prepare the backup. xtrabackup --prepare --target-dir=/var/lib/mysql volumeMounts: - name: data mountPath: /var/lib/mysql subPath: mysql - name: conf mountPath: /etc/mysql/conf.d containers: - name: mysql image: mysql:5.7 env: - name: MYSQL_ROOT_PASSWORD value: "123", - name: MYSQL_REPLICATION_USER value: "sync", - name: MYSQL_REPLICATION_PASSWORD value: "sync", ports: - name: mysql containerPort: 3306 volumeMounts: - name: data mountPath: /var/lib/mysql subPath: mysql - name: conf mountPath: /etc/mysql/conf.d resources: requests: cpu: 500m memory: 1Gi livenessProbe: exec: command: ["mysqladmin", "-uroot", "-p123", "ping"] initialDelaySeconds: 30 periodSeconds: 10 timeoutSeconds: 5 readinessProbe: exec: # Check we can execute queries over TCP (skip-networking is off). command: ["mysql", "-h", "127.0.0.1", "-uroot", "-p123", "-e", "SELECT 1"] initialDelaySeconds: 5 periodSeconds: 2 timeoutSeconds: 1 - name: xtrabackup image: gcr.io/google-samples/xtrabackup:1.0 ports: - name: xtrabackup containerPort: 3307 command: - bash - "-c" - | set -ex cd /var/lib/mysql # Determine binlog position of cloned data, if any. if [[ -f xtrabackup_slave_info ]]; then # XtraBackup already generated a partial "CHANGE MASTER TO" query # because we're cloning from an existing slave. mv xtrabackup_slave_info change_master_to.sql.in # Ignore xtrabackup_binlog_info in this case (it's useless). rm -f xtrabackup_binlog_info elif [[ -f xtrabackup_binlog_info ]]; then # We're cloning directly from master. Parse binlog position. [[ `cat xtrabackup_binlog_info` =~ ^(.*?)[[:space:]]+(.*?)$ ]] || 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 -uroot -p123 -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 -uroot -p123 < 这里使用了两个初始化容器.
第一个初始化容器init-mysql作用包括根据pod名称后缀生成server_id文件, 从configmap中获取指定配置. 这里默认StatefulSet控制的第一个pod即mysql-0为master, 其余为slave. 第二个clone-mysql使用开源工具xtrabackup, 用于当前slave从前一个slave复制数据, 当有新的作为slave的pod加入集群时, 这个pod会从上一个pod(序号小1)的非master的pod复制数据, 因为新pod加入时, 我们必须假定master中的数据是不为空的, 需要进行一次复制操作, 这样在扩容时会避免数据丢失,而从前一个pod复制数据是因为StatefulSet按顺序启动, 当前一个pod为ready时才启动后一个pod的机制而来.当init容器执行完成后, 常规容器开始启动并运行. mysql Pods由运行mysqld服务的mysql容器和充当SideCar的xtrabackup容器组成(挎斗模式解析请见)。
# Client service for connecting to any MySQL instance for reads.# For writes, you must instead connect to the master: mysql-0.mysql.apiVersion: v1kind: Servicemetadata: name: mysql-access labels: app: mysqlspec: ports: - name: mysql port: 3306 selector: app: mysql
root@node4:~# kubectl -n admin-d2069c get pvc,pv,statefulset,pod,service,configmap |grep mysqlpvc/storage-mysql-0 Bound pvc-bb591208-c2f4-11e8-b599-0050568eef9f 512M RWX managed-nfs-storage 12mpvc/storage-mysql-1 Bound pvc-c4ada169-c2f4-11e8-b599-0050568eef9f 512M RWX managed-nfs-storage 12mpvc/storage-mysql-2 Bound pvc-ce20ad71-c2f4-11e8-b599-0050568eef9f 512M RWX managed-nfs-storage 11mpv/pvc-bb591208-c2f4-11e8-b599-0050568eef9f 512M RWX Delete Bound admin-d2069c/storage-mysql-0 managed-nfs-storage 12mpv/pvc-c4ada169-c2f4-11e8-b599-0050568eef9f 512M RWX Delete Bound admin-d2069c/storage-mysql-1 managed-nfs-storage 12mpv/pvc-ce20ad71-c2f4-11e8-b599-0050568eef9f 512M RWX Delete Bound admin-d2069c/storage-mysql-2 managed-nfs-storage 11mstatefulsets/mysql 3 3 12mpo/mysql-0 2/2 Running 0 12mpo/mysql-1 2/2 Running 0 12mpo/mysql-2 2/2 Running 0 11msvc/mysql ClusterIP None3306/TCP 12msvc/mysql-access ClusterIP 10.68.8.223 3306/TCP 12mcm/mysql 2 12m
登录mysql-0, 执行
kubectl -n admin-d2069c exec -it mysql-0 /bin/bash
进入mysql-0后连接mysql:
mysql -p123
创建database, 并以同样方式登录mysql-1或mysql-2, 发现其下已经将新创建的database同步则为验证成功.
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