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Instrumentation Process

Asynchronous instrumentation (default)

The approach inspectIT Ocelot takes for instrumenting is fundamentally different from the approach of most other JVM instrumentation agents. InspectIT Ocelot does not instrument classes when they are loaded, the instrumentation is performed purely asynchronous in the background.

In this background task inspectIT Ocelot essentially looks at every loaded class and performs an instrumentation if required by the active configuration. Hereby, the agent manages the classes he has to analyze in a queue. This queue is processed in batches to ensure that no CPU resources are blocked if they are required by the instrumented application. The batching is configurable using the internal settings.

If the instrumentation uses actions, inspectIT Ocelot will inject new classes into target classloaders, which implement these actions. In case actions exist, which are no longer used, the injected classes implementing these actions are considered as orphans. Such orphan classes cannot be garbage collected. Thus, inspectIT Ocelot will attempt to recycle such classes for new actions. If this feature causes exceptions, you can disable the recycling of old action classes.

inspectit:
  instrumentation:
    # settings for fine-tuning the instrumentation process
    internal:
      # the time to pause between executing batches of class instrumentation updates
      inter-batch-delay: 50ms
      # defines how many classes are checked at once for updates of their configuration per batch
      class-configuration-check-batch-size: 1000
      # defines the maximum number of classes which are instrumented per batch
      class-retransform-batch-size: 10

      # defines how often the agent should check if new classes have been defined.
      new-class-discovery-interval: 10s
      # defines how often the new class discovery is performed after a new class has been loaded
      num-class-discovery-trials: 2
      
      # defines whether orphan action classes are recycled or new classes should be injected instead
      recyclingOldActionClasses: true

In addition, the size of the instrumentation queue can be used as an indicator for the instrumentation progress. It is accessible via the self-monitoring of the agent.

InspectIT allows you to perform instrumentation by injecting custom code into your application. If your JVM has a SecurityManager enabled, you might also want to control the ProtectionDomain of these injected classes.

By default, inspectIT will use its own ProtectionDomain for injected classes. Alternatively, you can make inspectIT to use the ProtectionDomain for which the action is being created using the following configuration:

inspectit:
  instrumentation:
    internal:
      use-inspectit-protection-domain: false

Synchronous instrumentation (BETA!)

caution

Enabling synchronous instrumentation in Java 8 environments will result in significant boot time performance degradation!

See: JDK-7018422

By default, all instrumentation is performed purely asynchronously in the background. There may be situations where this is not appropriate and a class must be instrumented directly at the first load, e.g. in batch processes.

InspectIT can be configured to instrumented classes on first class load by updating the following configuration:

inspectit:
  instrumentation:
    internal:
      async: false