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Re: Recommendation for running a MySQL cluster on 3 servers
Posted by: Jon Stephens
Date: June 22, 2018 04:15AM

The loss of a management node or SQL/API node should not bring down the cluster.

The STOP command has a built-in safety feature, which you can use to find out whether the loss of a given data node would bring down the cluster, like this:

ndb_mgm> SHOW
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=5    @127.0.0.1  (mysql-5.7.23 ndb-7.6.8, Nodegroup: 0, *)
id=6    @127.0.0.1  (mysql-5.7.23 ndb-7.6.8, Nodegroup: 0)

[ndb_mgmd(MGM)] 1 node(s)
id=50   @127.0.0.1  (mysql-5.7.23 ndb-7.6.8)

[mysqld(API)]   2 node(s)
id=100 (not connected, accepting connect from 127.0.0.1)
id=101 (not connected, accepting connect from any host)

ndb_mgm> 5 STOP
Node 5: Node shutdown initiated

Node 5: Node shutdown completed.
Node 5 has shutdown.

ndb_mgm> SHOW
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=5 (not connected, accepting connect from 127.0.0.1)
id=6    @127.0.0.1  (mysql-5.7.23 ndb-7.6.8, Nodegroup: 0, *)

[ndb_mgmd(MGM)] 1 node(s)
id=50   @127.0.0.1  (mysql-5.7.23 ndb-7.6.8)

[mysqld(API)]   2 node(s)
id=100 (not connected, accepting connect from 127.0.0.1)
id=101 (not connected, accepting connect from any host)

ndb_mgm> 6 stop
Node 6: Node shutdown aborted
Shutdown failed.
*  2002: Stop failed
*        Node shutdown would cause system crash: Permanent error: Application error

ndb_mgm> show
Cluster Configuration
---------------------
[ndbd(NDB)]     2 node(s)
id=5 (not connected, accepting connect from 127.0.0.1)
id=6    @127.0.0.1  (mysql-5.7.23 ndb-7.6.8, Nodegroup: 0, *)

[ndb_mgmd(MGM)] 1 node(s)
id=50   @127.0.0.1  (mysql-5.7.23 ndb-7.6.8)

[mysqld(API)]   2 node(s)
id=100 (not connected, accepting connect from 127.0.0.1)
id=101 (not connected, accepting connect from any host)

cheers

Jon Stephens
MySQL Documentation Team @ Oracle
Orlando, Florida, USA

MySQL Dev Zone
MySQL Server Documentation
Oracle

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Re: Recommendation for running a MySQL cluster on 3 servers
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June 22, 2018 04:15AM


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