MySQL Enterprise Monitor 8.0.16 Manual

18.3 Advisor Thresholds

Thresholds are the predefined limits for Advisors. If the monitored value breaches the defined threshold, an event is generated and displayed on the Events page for the asset.

Advisor thresholds use a variety of different value types, depending on the monitored value. Some use percentages, such as percentage of maximum number of connections. Others use timed durations, such as the average statement execution time. It is also possible to check if specific configuration elements are present or correct.

The following thresholds, listed in order of severity, can be defined for most Advisors:

Note

Not all Advisors require threshold parameters, others do not have any parameters, such as the Graphing Advisors.

The following image shows an example of threshold definitions on the Parameters tab of an advisor:

Figure 18.6 Threshold Definitions Example

Example of advisor threshold definitions.

The values shown are taken from the Availability Advisor, Maximum Connection Limit Nearing or Reached. The values define the percentage of maximum connections at which an event is logged. For example:

Time-based Thresholds

The majority of the time-based thresholds use simple duration values, such as seconds, minutes and so on. These are used to monitor such values as system uptime and, if the value for uptime drops below a certain value, indicating a restart, trigger an event.

Others use an Exponential Moving Average Window, which monitors values over a predefined time period. One such advisor is the CPU Utilization Advisor. The moving average window is used because CPU utilization can spike many times a minute, for a variety of different reasons. Raising an event for each spike would not be useful. The moving average enables you to monitor CPUs for long durations and take an average CPU utilization across that duration. Thresholds are defined against that average.

Percentage-based Thresholds

Percentage-based thresholds trigger events based on percentages of a server-defined value. Maximum number of connections, for example, raises events based on a percentage value of the total number of connections to the monitored instance or group.

Text-based Thresholds

Text-based thresholds are used to check specific configuration values are properly defined, or to retrieve success or failure messages for system processes such as backups.