准备使用集群的时候发现集群起不来，
发现抱错集群各个节点都是readonly 状态，找了很多资料，由于集群处于不一致的情况需要防止不同的节点数据写入脏数据
取消节点readonly 方法如下：
MySQL 取消 super read only
直接关闭read only 模式
SET GLOBAL super_read_only = OFF;
登录 mysqlsh 执行
dba.configureLocalInstance()
Dba.configureLocalInstance: This function is not available through a session to an instance belonging to an unmanaged asynchronous replication topology (RuntimeError)
shell.connect('root@node1:3306')
Creating a session to 'root@node1:3306'
Fetching schema names for autocompletion... Press ^C to stop.
Closing old connection...
Your MySQL connection id is 215
Server version: 8.0.30 MySQL Community Server - GPL
No default schema selected; type \use <schema> to set one.
看到一个帖子说创建了一个集群就好了
开始创建集群：
var cluster = dba.createCluster('testCluster')
A new InnoDB Cluster will be created on instance 'node1:3306'.
Disabling super_read_only mode on instance 'node1:3306'.
Validating instance configuration at node1:3306...
This instance reports its own address as node1:3306
Instance configuration is suitable.
NOTE: Group Replication will communicate with other members using 'node1:3306'. Use the localAddress option to override.
Creating InnoDB Cluster 'testCluster' on 'node1:3306'...
Adding Seed Instance...
NOTE: User 'mysql_innodb_cluster_1891693795'@'%' already existed at instance 'node1:3306'. It will be deleted and created again with a new password.
Cluster successfully created. Use Cluster.addInstance() to add MySQL instances.
创建成功，添加实例
cluster.addInstance('root@node2:3306');
结果报错：
cluster.addInstance('root@node2:3306');
WARNING: A GTID set check of the MySQL instance at 'node2:3306' determined that it contains transactions that do not originate from the cluster, which must be discarded before it can join the cluster.
node2:3306 has the following errant GTIDs that do not exist in the cluster:
45fc6a70-48a9-11ed-adfc-000c29325d80:1
WARNING: Discarding these extra GTID events can either be done manually or by completely overwriting the state of node2:3306 with a physical snapshot from an existing cluster member. To use this method by default, set the 'recoveryMethod' option to 'clone'.
Having extra GTID events is not expected, and it is recommended to investigate this further and ensure that the data can be removed prior to choosing the clone recovery method.
Please select a recovery method [C]lone/[A]bort (default Abort): C
Validating instance configuration at node2:3306...
This instance reports its own address as node2:3306
Instance configuration is suitable.
NOTE: Group Replication will communicate with other members using 'node2:3306'. Use the localAddress option to override.
A new instance will be added to the InnoDB cluster. Depending on the amount of
data on the cluster this might take from a few seconds to several hours.
Adding instance to the cluster...
NOTE: User 'mysql_innodb_cluster_1780669600'@'%' already existed at instance 'node1:3306'. It will be deleted and created again with a new password.
Monitoring recovery process of the new cluster member. Press ^C to stop monitoring and let it continue in background.
Clone based state recovery is now in progress.
NOTE: A server restart is expected to happen as part of the clone process. If the
server does not support the RESTART command or does not come back after a
while, you may need to manually start it back.
* Waiting for clone to finish...
NOTE: node2:3306 is being cloned from node1:3306
** Stage DROP DATA: Completed
** Clone Transfer
FILE COPY ############################################################ 100% Completed
PAGE COPY ############################################################ 100% Completed
REDO COPY ############################################################ 100% Completed
NOTE: node2:3306 is shutting down...
* Waiting for server restart... ready
* node2:3306 has restarted, waiting for clone to finish...
** Stage RESTART: Completed
* Clone process has finished: 75.75 MB transferred in about 1 second (~75.75 MB/s)
State recovery already finished for 'node2:3306'
The instance 'node2:3306' was successfully added to the cluster.
实例中有的gts没同步过来，需要同步选择C 复制过来，第二个实例也添加成功了
再添加第三个实例
查看集群状态
cluster.status();
cluster.status();
{
"clusterName": "testCluster",
"defaultReplicaSet": {
"name": "default",
"primary": "node1:3306",
"ssl": "REQUIRED",
"status": "OK",
"statusText": "Cluster is ONLINE and can tolerate up to ONE failure.",
"topology": {
"node1:3306": {
"address": "node1:3306",
"memberRole": "PRIMARY",
"mode": "R/W",
"readReplicas": {},
"replicationLag": "applier_queue_applied",
"role": "HA",
"status": "ONLINE",
"version": "8.0.30"
},
"node2:3306": {
"address": "node2:3306",
"memberRole": "SECONDARY",
"mode": "R/O",
"readReplicas": {},
"replicationLag": "applier_queue_applied",
"role": "HA",
"status": "ONLINE",
"version": "8.0.30"
},
"node3:3306": {
"address": "node3:3306",
"memberRole": "SECONDARY",
"mode": "R/O",
"readReplicas": {},
"replicationLag": "applier_queue_applied",
"role": "HA",
"status": "ONLINE",
"version": "8.0.30"
}
},
"topologyMode": "Single-Primary"
},
"groupInformationSourceMember": "node1:3306"
}
集群状态运行正常