Maxscale, ranks and priority

Question

I'm using a maxscale (6.2) readwritesplit router with 3 galera servers (mariadb 10.4). 2 of them are in DC1, and a 3rd one is on a distant DC2.

Using ranks is the only option I see here, as priority will be used by galeramon to select the master.

My goal is to tell maxscale to use DC1 as much as possible, so server1 as master (priority=1, rank=primary), server2 as slave (priority=2, rank=primary), and use DC2 server3 only if server1 or server2 are not reachable (priority=3, rank=secondary).

Is this the correct behavior?

[server1]
type=server
address=192.168.0.11
priority=1
rank=primary

[server2]
type=server
address=192.168.0.12
priority=2
rank=primary

[server3]
type=server
address=192.168.0.21
priority=3
rank=secondary

[split]
type=service
router=readwritesplit
servers=server1,server2,server3

[monitor]
type=monitor
module=galeramon
servers=server1,server2,server3
root_node_as_master=true
use_priority=true

You don't need `root_node_as_master=true` if you use priorities as the priority mechanism overrides all other monitoring logic. — markusjm, Feb 22 '22 at 12:53

score 1 · Accepted Answer · answered Feb 22 '22 at 12:57

1

Yes, the readwritesplit module only uses connections that have the same rank. This means that if both server1 and server2 fail, the readwritesplit service will use server3 as long as it is up.

When either of the two other servers comes back up, the galeramon monitor will shift the Master label from server3 to one of the other nodes. At that point readwritesplit will discard the connection to server3 and reconnect to the nodes with the higher rank, if possible.

answered Feb 22 '22 at 12:57

markusjm

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Thanks markus. What happens if server2 fails? Will server1 get reads and writes, or will writes go to server1 and reads to server3? – CrazyRabbit Feb 22 '22 at 14:07
1

All traffic will go to server1 at that point. – markusjm Feb 23 '22 at 07:52

Maxscale, ranks and priority

1 Answers1