How to add a node into a worked xtradbcluster？

##摘之percona 论坛

if you initialized the first PXC node, so it's standalone primary node, then adding new nodes is very simple. On a new node, you just specify the existing node's IP in this variable: 
wsrep_cluster_address=gcomm://node1_IP  
Then full SST will copy data from existing node to a new node, eventually making both nodes identical.
Once all machines are joined into a cluster, then add all the IPs in the my.cnf on each node 

wsrep_cluster_address=gcomm://IP1,IP2,IPn 



##我实践过了，按照上面的方式是可以的！