What is a sensor?
A Sensor is a small piece of code that instuments the monitored applications at certain points to extract the relevant data. For example, a Sensor can transport tagging information from one host to another when a web service call is executed. The AppMon installation includes a set of built-in Knowledge Sensor Packs for a wide set of application servers and frameworks. These Knowledge Sensor Packs are maintained by AppMon. You can activate/deactivate them as needed.
Hot Sensor Placement
Whenever a class is loaded in a monitored application, the Agent sends this class over the network to the AppMon Collector for instrumentation. Sensors are injected if necessary. The class is sent back to the Agent if it has been manipulated. If a sensor is placed or removed while the monitored application is running, you must reload the affected classes to enforce re-instrumentation. This Hot Sensor Placement is provided as an explicit operation in Sensor maintenance.
An entry point is the starting point of a new PurePath. It is defined by a placed and active sensor with the appropriate configuration. For most users, the Knowledge Sensor Packs already define the correct entrypoints. See Sensor Configuration for more information.
AppMon provides additional information on PurePaths without the need to do specific configuration. Auto Sensors automatically retrieve additional call hierarchy information and place this information on the respective PurePaths. This information includes class and method names, parameter and return types, and access modifiers. Auto Sensors are enabled by default.
Because Auto Sensors do not inject code into the monitored application, the timing information that is provided is not as accurate as the timing information delivered by explicitly placed Sensors.
The following figure illustrates the information captured by Auto Sensors.
Auto Sensor resolution
Auto Sensors adjust automatically to ensure they do not incur more overhead than the percentage setting. The amount of detail captured depends on the complexity of the application or environment. You may need to adjust the resolution settings until you see the desired level of detail for a tolerable amount of overhead. See Agent Group - Agent Mapping Advanced Settings to learn how to adjust sensor resolution.
You can manually create additional sensors by defining Sensor rules. Sensor Rules specify a Sensor's location through class and method patterns. The rules also enable the Sensor to access data such as method parameters or return values. User-defined Sensors are typically used to specify additional Entrypoints or access specific information in a method's parameters. See Sensor Configuration for more information.