The frequency and thresholds defined for a rule are default
recommendations. To edit these properties choose the
Create/Edit Rule
link.
The following image shows the screen used to edit rules:
Beside the rule name is the Advisor
drop-down
list box, used for setting the advisor group. This list box shows
existing groupings and any you may have added. The
Expression
textarea shows the advisor rule,
Variable Assignment
the data item associated
with variable(s) used in the rule and
Thresholds
determines when to trigger each
alert type.
The three levels of Thresholds
are
Info Alert
, Warning Alert
,
and Critical Alert
indicating increasing levels
of severity. Levels can be triggered by the expression result
being equal to a certain value, greater than a certain value, or
less than a certain value.
The data items that variables are associated with are operating
system (OS) properties such as available RAM or MySQL
characteristics such as the InnoDB buffer pool. To see all
available data items drop down the Data Item
list box. For a listing of these data items see
Data Collection Items.
In Figure 15.43, “MySQL Enterprise Dashboard: Editing Rules” the drop-down
Data Item
list box within the Variable
Assignment
frame shows the various MySQL server status
or operating system specific variables that may be used in
expressions. The text boxes below Thresholds
define the levels at which informational, warning, or critical
alerts are issued.
To lower the threshold for an informational alert, simply increase
the number given in the Info Alert
text box.
When a data item can apply to multiple objects, you need to
specify which instance to use for that item, hence the
Instance
text box. In almost all cases this
should be set to local
. The exceptions are as
follows:
For CPU-related items set Instance to
cpu0
. Additional CPUs on a system are
referred to as cpu1, cpu2
and so on.
There can be multiple disks mounted on a system. To refer to
a specific drive set Instance to the
name of of the mounted drive. On Windows this would be
C:, D:
, and so on. On Unix systems, use
whatever is valid for the df command.
For RAM-related items set Instance to
mem
.
Where there are table-specific variables, the database name and table name must be specified in the Instance text box. This topic is discussed in detail in what follows.
It is not possible to have a data item that is unrelated to an
instance. This raises the error, You must map
"<variable>" to an instance
, and you will be
unable to save the rule.
An agent can only collect data from one MySQL server, so the
instance
entry for a variable in a rule does
not need to specify which MySQL server to use; no matter how many
servers are being monitored there is always a one-to-one
relationship between an agent and its monitored server.
However, on one server there may be multiple occurrences of a
variable. For example, there are multiple possible occurrences of
table-specific variables such as Avg_row_length
because there can be multiple databases and tables defined in a
MySQL server. In this case, the “instance” refers to
the database and table that a data item should be associated with,
specified in the form
databasename
.tablename
.
So, for example, if you want to reference the
Avg_row_length
of the mysql
database user
table in an expression, select
the mysql:tablestatus:Avg_row_length
from the
Data Item list box and specify
mysql.user
in the Instance
text box.
On the other hand, in the case of a global server variable, there
is only one possible target. For example, there can only be one
instance of delay_key_write
because this
variable is global and applies to the server as a whole. In this
case specify local
in the
Instance text box.
To save your changes click the save button at the bottom of the page.
You can change only the thresholds and the frequency of built-in rules. So that rules function properly when updated, other changes are prohibited.
Should you wish to make other changes to a built-in rule, copy it and modify it as desired.
You can edit a rule even if it is currently scheduled. Your
changes will not be overwritten when new rules are imported using
the Check for Updates
link.
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