参考链接：https://kubernetes.io/docs/tasks/run-application/run-replicated-stateful-application/
一、创建ConfigMap
apiVersion: v1
kind: ConfigMap
metadata:
name: mysql
labels:
app: mysql
data:
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.
二、创建headless service
# Headless service for stable DNS entries of StatefulSet members.
apiVersion: v1
kind: Service
metadata:
name: mysql
labels:
app: mysql
spec:
ports:
- name: mysql
port: 3306
clusterIP: None
selector:
app: mysql三、创建StatefulSet
apiVersion: apps/v1beta1
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: mysql
spec:
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 <<EOF
$(<change_master_to.sql.orig),
MASTER_HOST='mysql-0.mysql',
MASTER_USER='root',
MASTER_PASSWORD='123',
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 --password=123"
volumeMounts:
- name: data
mountPath: /var/lib/mysql
subPath: mysql
- name: conf
mountPath: /etc/mysql/conf.d
resources:
requests:
cpu: 100m
memory: 100Mi
volumes:
- name: conf
emptyDir: {}
- name: config-map
configMap:
name: mysql
volumeClaimTemplates:
- metadata:
name: data
spec:
accessModes: ["ReadWriteOnce"]
resources:
requests:
storage: 10Gi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http://www.mamicode.com/info-detail-2149700.html)。
四、创建用于访问Service
# Client service for connecting to any MySQL instance for reads.
# For writes, you must instead connect to the master: mysql-0.mysql.
apiVersion: v1
kind: Service
metadata:
name: mysql-access
labels:
app: mysql
spec:
ports:
- name: mysql
port: 3306
selector:
app: mysql五、查看
root@node4:~# kubectl -n admin-d2069c get pvc,pv,statefulset,pod,service,configmap |grep mysql
pvc/storage-mysql-0 Bound pvc-bb591208-c2f4-11e8-b599-0050568eef9f 512M RWX managed-nfs-storage 12m
pvc/storage-mysql-1 Bound pvc-c4ada169-c2f4-11e8-b599-0050568eef9f 512M RWX managed-nfs-storage 12m
pvc/storage-mysql-2 Bound pvc-ce20ad71-c2f4-11e8-b599-0050568eef9f 512M RWX managed-nfs-storage 11m
pv/pvc-bb591208-c2f4-11e8-b599-0050568eef9f 512M RWX Delete Bound admin-d2069c/storage-mysql-0 managed-nfs-storage 12m
pv/pvc-c4ada169-c2f4-11e8-b599-0050568eef9f 512M RWX Delete Bound admin-d2069c/storage-mysql-1 managed-nfs-storage 12m
pv/pvc-ce20ad71-c2f4-11e8-b599-0050568eef9f 512M RWX Delete Bound admin-d2069c/storage-mysql-2 managed-nfs-storage 11m
statefulsets/mysql 3 3 12m
po/mysql-0 2/2 Running 0 12m
po/mysql-1 2/2 Running 0 12m
po/mysql-2 2/2 Running 0 11m
svc/mysql ClusterIP None <none> 3306/TCP 12m
svc/mysql-access ClusterIP 10.68.8.223 <none> 3306/TCP 12m
cm/mysql 2 12m
六、测试集群
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.