> ## Documentation Index
> Fetch the complete documentation index at: https://docs.odigos.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Custom Instrumentation

> The "Custom Instrumentation" rule can be used to define custom eBPF-based instrumentations for arbitrary functions in your application code or its dependencies.

## Considerations

If you wish to create custom eBPF-based instrumentations for Go or Java applications, you can define a "Custom Instrumentation" rule via the Odigos InstrumentationRule CRD or the Odigos UI.

This feature is a great way to extend Odigos's auto-instrumentation capabilities to cover your specific use cases and application logic.

## Configuration Options

<AccordionGroup>
  <Accordion title="Golang">
    <Warning>
      When `function` is specified, `receiverName` and `receiverMethodName` must NOT be specified, and vice versa, if `receiverName` and `receiverMethodName` are specified, `function` must NOT be specified.

      `PackageName` is required in all cases.
    </Warning>

    <AccordionGroup>
      <Accordion title="packageName">
        **packageName** `string` - The name of the package containing the function to instrument.

        * This field is *required*
      </Accordion>

      <Accordion title="functionName">
        **functionName** `string` - The name of the function to instrument.

        * This field is *optional*
      </Accordion>

      <Accordion title="receiverName">
        **receiverName** `string` - The name of the receiver type if the function is a method.

        * This field is *optional*
      </Accordion>

      <Accordion title="receiverMethodName">
        **receiverMethodName** `string` - The name of the method receiver if the function is a method.

        * This field is *optional*
      </Accordion>
    </AccordionGroup>
  </Accordion>

  <Accordion title="Java">
    <AccordionGroup>
      <Accordion title="class">
        **class** `string` - The fully qualified name of the class containing the method to instrument.

        * This field is *required*
      </Accordion>

      <Accordion title="method">
        **method** `string` - The name of the method to instrument.

        * This field is *required*
      </Accordion>
    </AccordionGroup>
  </Accordion>
</AccordionGroup>

## Basic Example

The following example shows how to create a "Custom Instrumentation" rule that instruments a function named `ProcessOrder` in the `github.com/example/ecommerce` package.

<Steps>
  <Step>
    Create a YAML file named `custom-instrumentation.yaml` with the following content:

    <Accordion title="Package and function(golang)">
      ```yaml theme={null}
      apiVersion: odigos.io/v1alpha1
      kind: InstrumentationRule
      metadata:
          name: custom-instrumentation-rule
          namespace: odigos-system
      spec:
          ruleName: "Custom Instrumentation for ProcessOrder"
          customInstrumentation:
              golang:
                  packageName: "github.com/example/ecommerce"
                  functionName: "ProcessOrder"
      ```
    </Accordion>

    <Accordion title="Receiver method(golang)">
      ```yaml theme={null}
      apiVersion: odigos.io/v1alpha1
      kind: InstrumentationRule
      metadata:
          name: custom-instrumentation-rule
          namespace: odigos-system
      spec:
          ruleName: "Custom Instrumentation for ProcessOrder Method"
          customInstrumentation:
              golang:
                  packageName: "github.com/example/ecommerce"
                  receiverName: "OrderProcessor"
                  receiverMethodName: "ProcessOrder"
      ```
    </Accordion>
  </Step>

  <Step>
    Apply the action to the cluster:

    ```shell theme={null}
    kubectl apply -f custom-instrumentation.yaml
    ```
  </Step>
</Steps>