This section describes how the inspectIT Ocelot Java agent can be used to inject predefined or custom monitoring code into the target application.
InspectIT Ocelot gives you a very large degree of freedom when it comes to defining instrumentation. The first step is usually defining your scopes. A scope acts as a selector for finding the methods you want to instrument.
Scopes are then used by rules. While scopes define which methods you instrument, rules define the actual monitoring actions which will be performed. Examples for such actions would be recording the response time or extracting the HTTP url for further processing.
For the definition of rules, actions are a key concept. Long story short: actions allow you to specify Java snippets in your configuration which will be executed to extract any data you want. This can be performance data such as the response time or any kind of business data, e.g. the shopping cart size.
All instrumentation settings can be changed without restarting the application!
They can even be changed while a previous instrumentation is still in progress. In this case the inspectIT Ocelot agent will automatically switch to the new instrumentation as soon as the configuration is loaded.
Disabling the Instrumentation
1.12.2, the agent provides the option to disable its instrumentation process.
When disabled, the agent will revert any instrumentations done and restore the original state of all instrumented classes.
This would be like having no single rule (also none in the agent's default configuration) defined.
This results in no more runtime data (traces and metrics) being recorded from executed methods.
Metrics which are not based on instrumentations like e.g. JVM internals (thread statistics, memory statistics, ...) are not affected by this option.
Differentiating between rules, actions and scopes as well as differentiating between keys and values in the configuration can be tricky from time to time. Therefore, to increase readability of your configuration files the following naming convention is recommended:
- Scope names always start with
- Action names always start with
- Rule names always start with
- Context variables names should start with
- Fields which are defined by the user should always be put in single quotations marks, e.g.
input: 'my_input'. This rule also applies to keys which can be entirely defined by the user, for example when defining the name of a custom action or attribute names.
This naming convention is used both in this documentation and the default configuration provided.