When defining a new alert, you have to define at least one condition that describes when the alert should be raised. If more conditions are specified, all must be fulfilled for an alert to be raised.
There are three condition types you can choose: value, baseline and cut-off condition.
Use it to specify a constant threshold value for the metric or metric expression.
By defining two value conditions for a selected metric, you can specify a range of values. For example, if one condition set to
greater than or equal to 100, and the other to
less than or equal to 200, it means all values between 100 and 200, including 100 and 200.
You can define maximum two value conditions for your alert.
Use it to compare the metric value with the calculated baseline value (see Baseline data), usually multiplied by a specified number (baseline multiplier).
In the single alert comparison mode, the current value of the metric being monitored is compared with the baseline value multiplied by the baseline multiplier . For example, for a metric measuring the number of transactions,
greater than 2 means that for the alert to be raised the number of transaction must be greater than two baseline values .
In the absolute or relative alert comparison modes, the calculated absolute or relative value of metric increment is compared to the specified percentage value .
The baseline condition may be accompanied by a value condition. For example, if the value condition is set to
greater than 500 and the baseline condition is set to greater than 2, the alert will be raised when the number of transactions exceeds two baseline values and it also must exceed the absolute value of 500 transactions.
Baseline condition is only available if the alert detector settings includes at least one dimension or combination of dimensions from the predefined list. For more information, see Limitations on using baseline conditions.
You can only define 1 baseline condition.
Use it to eliminate false alerts being triggered by insignificant changes of the monitored metric. For example, an increase in response time from 0.1 ms to 0.5 ms (milliseconds) may appear to be a substantial change (400%), but in real terms it is only 0.4 ms, which might be insignificant. Setting the cut-off condition for response time to
>1 will ensure that the change in the metric will be considered only for values above 1 ms.
This condition applies only to the last monitoring interval, and is available only for differential—absolute and relative—comparison modes. You can define maximum two cut-off thresholds for a selected metric.
Availability of conditions for different comparison modes
The availability of condition types is affected by the selected comparison mode in the alert detector settings. A comparison mode describes how the current metric values are compared against thresholds or baselines. Depending on the nature of the metric, you can monitor whether its value simply exceeds another predefined value (single mode), or you can monitor how much the value changed over time, as compared with how fast the baseline changed for the corresponding period of time (absolute and relative mode).
Combinations of conditions allowed in the single comparison mode:
Value and baseline
Combinations of conditions allowed in the absolute and relative comparison modes:
Value and baseline
Value and cut-off
Baseline and cut-off
Value, baseline and cut-off
The comparison mode is not the only element that may limit the use of some conditions. As mentioned in the note above, baseline condition is only available if the alert detector settings includes at least one dimension or combination of dimensions from the predefined list. For more information, see Limitations on using baseline conditions.