Redundant management nodes in MySQL Cluster-优快云博客

本文详细介绍了如何在MySQL集群环境中为管理节点设置冗余，并实现故障转移，确保集群的高可用性和稳定性。通过在配置文件中添加多个管理节点实例，配置管理节点间的连接字符串，以及确保所有管理节点配置一致，可以轻松实现这一目标。

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Every time I teach the MySQL Cluster architecture, someone inevitably asks "Isn't the management node (ndb_mgmd) a single point of failure?" The short answer: no. The management node is not a SPOF because the cluster can continue without it. However, it's inconvenient if your management node is down because the management node does several things such as:

Provide status information about the cluster and allow you to use the ndb_mgm for various maintenance tasks like taking a hot backup
Own the cluster config file (therefore it must be running to start a node)
Arbitration in case of a potential split-brain
Logging

So while the management node can be down, it is nice to have a redundant one for failover. This is very easy to do:

Add 2 [NDB_MGMD] sections to config.ini:
[NDB_MGMD]
#Id is required when defining multiple mgmt nodes
Id=1
Hostname=192.168.0.31

[NDB_MGMD]
Id=2
Hostname=192.168.0.32
Change the ndb-connectstring to include both IPs of the management nodes:
[mysql_cluster]
ndb-connectstring=192.168.0.31,192.168.0.32
Make sure the config.ini is on both management nodes and that the files are identical. Start both ndb_mgmd nodes.

That's it! The management nodes will act in an active-passive way and failover as necessary. Make sure you do not run any management node on the same physical host as a data node - it will cause a cluster shutdown if they fail simultaneously.