Confusion on Mysql Management node? Where to run queries?



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    This is a great question, many have it so thanks for bringing it up here.

    Management servers (ndb_mgmd) are NOT involved in query handling and no queries/routing or whatever related to queries are relayed through the management serverrs, but it manages:

    • Cluster Configuration
    • Writes a log file (ndb cluster log)
    • .. and a couple of more things (network arbitration etc)
    Query processing is handled by the MySQL Servers connected to the Data Nodes. The MySQL Servers converts SQL to a protocol the data nodes understand (the api is called the NDBAPI).
    You typically have to MySQL Servers (for HA).
    You can LB over these two MySQL servers using e.g HaProxy or a Hardware LB.  Some SQL drivers like Connector/J + php mysqlnd have Load Balancing built in that can be used.

    Hope this helps.


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    Severalnines Support

    By the way, you can easily add HA Proxy to your MySQL Cluster or Galera deployment using these scripts:

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