Tracer (Pinot Service Provider Interface 0.12.1 API)

```
public interface Tracer
```
Tracer responsible for trace state management. Users can implement this to filter what data is recorded, choose what format it is reported in (e.g. logs, JFR events, in-memory) and where it goes.

Method Summary

Modifier and Type	Method	Description
`InvocationRecording`	`activeRecording()`
`default RequestScope`	`createRequestScope()`	Starts
`InvocationScope`	`createScope(Class<?> clazz)`
`void`	`register(long requestId)`	Registers the requestId on the current thread.
`void`	`unregister()`	Detach a trace from the current thread.

- Method Detail
  - register
```
void register(long requestId)
```
    Registers the requestId on the current thread. This means the request will be traced. TODO: Consider using string id or random id. Currently different broker might send query with the same request id.
    
    Parameters:
    
    requestId - the requestId
  - unregister
```
void unregister()
```
    Detach a trace from the current thread.
  - createScope
```
InvocationScope createScope(Class<?> clazz)
```
    Parameters:
    
    clazz - the enclosing context, e.g. Operator, PlanNode, BlockValSet...
    
    Returns:
    
    a new scope which MUST be closed on the current thread.
  - createRequestScope
```
default RequestScope createRequestScope()
```
    Starts
    
    Returns:
    
    the request record
  - activeRecording
```
InvocationRecording activeRecording()
```
    Returns:
    
    the active recording