Alarms, alerts, and gauges alert administrators to changes in server conditions that might require attention.
An alarm represents a stateful condition of the server or a resource that might indicate a problem, such as low disk space or external server unavailability.
Alarms have severity, name, and message. Alarms will always have a Condition property, and can have a Specific Problem or Resource property. If surfaced through SNMP, a Probable Cause property and Alarm Type property are also listed. You can configure alarms to generate alerts when the alarm's severity changes.
You can configure the Alarm Manager, which governs the actions performed when an alarm state is entered, through the dsconfig tool and the administrative console. A complete list of system alerts, alarms, and their severity is available in <server-root>/docs/admin-alerts-list.csv.
The server complies with the International Telecommunication Union CCITT Recommendation X.733 (1992) standard for generating and clearing alarms. If configured, entering or exiting an alarm state might result in one or more alerts.
An alarm state is exited when the condition no longer applies. An alarm_cleared alert type is generated by the system when an alarm's severity changes from a non-normal severity to any other severity. An alarm_cleared alert will correlate to a previous alarm when the Condition and Resource properties are the same. The Condition corresponds to the Summary column in the admin-alerts-list.csv file.
Like the Alerts Backend, which stores information in cn=alerts, the Alarm Backend stores information within the cn=alarms backend. Unlike alerts, alarm thresholds have a state over time that can change in severity and be cleared when a monitored value returns to normal. You can view alarms with the status tool. As with other alert types, you can configure alert handlers can to manage the alerts generated by alarms.
There are two alert types supported by the server: standard and alarm-specific.
The server constantly monitors for conditions that might need administrator attention, such as low disk space. For this condition, the standard alert is low-disk-space-warning, and the alarm-specific alert is alarm-warning.
You can configure the server to generate alarm-specific alerts as well as standard alerts. By default, standard alerts are generated for conditions internally monitored by the server. However, gauges can only generate alarm-alerts.
A gauge defines a set of threshold values with a specified severity that, when crossed, cause the server to enter or exit an alarm state.
Numeric gauges monitor continuous values like CPU load or free disk space. Indicator gauges monitor enumerated set of values such as 'server unavailable' or ‘server unavailable’. Gauges generate alarms when the gauge’s severity changes due to changes in the monitored value.
The server installs a set of gauges that are specific to the product and that can be cloned or configured through the dsconfig tool. You can tailor existing gauges to fit each environment by adjusting the update interval and threshold values. Configuration of system gauges determines the criteria by which alarms are triggered.
Use the Stats Logger to view historical information about the value and severity of all system gauges. For more information, see Profiling server performance using the Stats Logger.