One Problem description

mariadb There is one master and two slaves , Example ：

192.168.144.249

192.168.144.250

192.168.144.251

At first 249 This server is the main database ,250,251 It's from （ From the library read_only）, Then there was a master-slave switch ,250 It becomes the main library ,249,251 It automatically becomes 250 Slave Library . Then it restarted 250, Find out maxscale Displays the status of all three databases Slave,Running：

notice maxscale The following errors are reported in the log ：

    21 2022-06-16 01:00:50   warning: [mariadbmon] The current master server 'srv-cls01-02' is no longer valid because it is in read-only mode, but there is no valid alternative to swap to.
     22 2022-06-16 01:00:50   error  : [mariadbmon] No Master can be determined. Last known was 192.168.144.250:3306

Because there is no master database , As a result, the business cannot write data .

Two Cause of error

Restarting the database is fast , There is no time to trigger automatic database failover , Failed to promote the slave database to the master database . And it's rebooted 250 database , Will read the read-only configuration in the configuration file , therefore maxscale I don't know who the master database is , So all three are Slave,Running.

3、 ... and terms of settlement

Log in to the database , Change parameter configuration online ：

set global read_only=on;

Cancel database mariadb In the configuration file read_only To configure .

In order to avoid colleagues connecting directly to a slave database （ Not even maxscale The agent address of ） Made modifications , Lead to inconsistency between master and slave , Can limit only maxscale ip Connect to database ( establish host by maxscale The server ip Users of ), But this way , Connect from the client maxscale agent ip Will report a mistake ：

Need to be in maxscale Add a parameter to the listener in the configuration file , skip maxscale Authentication of account Authority ：

authenticator_options=skip_authentication=true

And then restart maxscale