An alarm represents a stateful condition of the server or a resource that may indicate a problem, such as low disk space or external server unavailability. 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. Gauges are used for monitoring continuous values like CPU load or free disk space (Numeric Gauge), or an enumerated set of values such as 'server unavailable' or ‘server unavailable’ (Indicator Gauge). Gauges generate alarms, when the gauge’s severity changes due to changes in the monitored value. Like alerts, alarms have severity (NORMAL, WARNING, MINOR, MAJOR, CRITICAL), name, and message. Alarms will always have a Condition property, and may have a Specific Problem or Resource property. If surfaced through SNMP, a Probable Cause property and Alarm Type property are also listed. Alarms can be configured to generate alerts when the alarm's severity changes. The Alarm Manager, which governs the actions performed when an alarm state is entered, is configurable through the dsconfig tool and Administrative Console. A complete listing of system alerts, alarms, and their severity is available in <server-root>/docs/admin-alerts-list.csv.
There are two alert types supported by the server - standard and alarm-specific. The server constantly monitors for conditions that may need attention by administrators, such as low disk space. For this condition, the standard alert is low-disk-space-warning, and the alarm-specific alert is alarm-warning. The server can be configured to generate alarm-specific alerts instead of, or in addition to, standard alerts. By default, standard alerts are generated for conditions internally monitored by the server. However, gauges can only generate alarm-alerts.
The Directory Proxy Server installs a set of gauges that are specific to the product and that can be cloned or configured through the dsconfig tool. Existing gauges can be tailored to fit each environment by adjusting the update interval and threshold values. Configuration of system gauges determines the criteria by which alarms are triggered. The Stats Logger can be used to view historical information about the value and severity of all system gauges.
The Directory Proxy Server is compliant with the International Telecommunication Union CCITT Recommendation X.733 (1992) standard for generating and clearing alarms. If configured, entering or exiting an alarm state can 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. Alarms can be viewed with the status tool. As with other alert types, alert handlers can be configured to manage the alerts generated by alarms.