Should my.cnf settings be applied to all Mysql databases in the cluster or only to the CM db?

[#1]

Hi,

We have two Mysql databases in our cluster, one on the CM host and one on the Namenode host where CDH databases are located (oozie, metastore, hue, etc...)

It is unclear to me whether mysql my.cnf settings specified here:

https://www.cloudera.com/documentation/enterprise/latest/topics/cm_ig_mysql.html#cmig_topic_5_5_2

are supposed to be applied only to the Mysql database that Cloudera Manager uses or also to the Mysql database the CDH componets are using.

Can someone clarify this?

[#2]

@ivten

Having two mysql databases are common in the cluster where you have HA setup for MySQL. It works as master/slave... with that said, you have to apply the required setting in both the mysql databases.

Note: Here i've mentioned the standard method. Please make sure they are master & slave by running the following commands. 

login as root to mysql and run 

show slave status\G;
show master status\G;

[#3]

To clarify we don't have HA setup for mysql, but do use external mysql database for CDH services, which is located on one of the namenodes (we have HA Hadoop cluster). Cloudera management services use another mysql database on another host. 

[#4 · Accepted solution]

@ivten,

The "recommended" my.cnf in the Cloudera documentation is intended, in general, as a suggestion for MySQL used by any role.  DBAs may adjust as needed or desired.