Types of anomalous behavior in Health Log Analytics
Anomalous behavior in a CI or a service can indicate an important issue. For example, a spike in the frequency or number of messages of a particular type can indicate a problem.
To build models of expected behavior, Health Log Analytics monitors the log stream to learn baselines for patterns, metrics, and gauges over various time periods. Time periods can be hourly, daily, weekly, or unlimited. Behavior that departs from the learned models is considered anomalous behavior.
Types of log property
Pattern
A pattern is a value or rate that repeats, whether in text, time, or relationships.
Meter
A meter property is a numeric or text value. For example, a status code, a response code, an action, or a pattern.
Gauge
A gauge property has a numerical value that is reported continuously. Gauge properties represent operations that consume resources. For example, CPU usage, memory usage, or response time.
How anomalies appear in Health Log Analytics
The Anomaly card illustrates the anomalous activity that led to the alert. The chart shows:
- Recent anomalous activity
- Expected behavior (the learned baseline)
- Baseline values from one day earlier
- Baseline values from the previous week
In this example, the system tracks the baseline rate (the average number of events per minute) for a specific log pattern. When this typically inactive log generates a spike in events, the system detects the deviation from the baseline and generates an alert.
Anomaly card identifies and illustrates anomalous behavior.
Kinds of anomalies
| Behavior | Description |
|---|---|
| New behavior | A pattern that has not ever been seen. The New Behavior alert type does not display a chart. |
| Signal dead/Stopped appearing | All pattern or log data from a source has stopped. There has been no signal for at least five minutes. |
| Signal alive/Appearing again | A pattern or log data from a "dead" source is appearing again. For a baseline of one hour, a pattern is "dead" if it appears less than once per minute. |
| Anomaly above average or below average | Activity that deviates from expected baseline behavior for pattern or meter or gauge metrics, such as keywords metrics or severity metrics. |
| Baseline reference increase or decrease | An increase or decrease in the value or volume of a log property as compared to the one-hour or one-week baseline. |
| Correlation of severity and keyword alerts | An increase in the volume of a severity level or keyword. |