MySQL Enterprise Monitor 8.0 Release Notes
When MySQL Enterprise Monitor evaluates an expression, it replaces variables with values. For example, part of the expression for the “MyISAM Key Cache Has Sub-Optimal Hit Rate” advisor calculates the hit rate as follows:
100-((%Innodb_buffer_pool_reads% / %Innodb_buffer_pool_read_requests%)*100)
If the current value of
%Innodb_buffer_pool_reads% is 4522 and the
current value of
%Innodb_buffer_pool_read_requests% is 125989,
the hit ratio is 96.4%:
100 -((4522 / 125989) * 100)
By convention, the Advisors supplied by MySQL use
% as the delimiter, for example,
%Key_reads%. This makes variables more
readily identifiable.
Variables can be used in the Description,
Advice, Action, and
Links attributes of a advisor, as well as in
expressions. This lets you report the current value of an
expression. For instance, you can add the message, “The
current value of Innodb_buffer_pool_reads is
%Innodb_buffer_pool_reads%.” to the
Advice text box. When this is displayed on
the screen, the value of
%Innodb_buffer_pool_reads% is substituted
into the text. If
%%Innodb_buffer_pool_reads%% has a value of
4522, the message becomes “The current
value of Innodb_buffer_pool_reads is 4522.”