[lttng-docs.git] / contents / understanding-lttng / core-concepts / domain.md

---
id: domain
---

A tracing _domain_ is the official term the LTTng project uses to
designate a tracer category.

There are currently four known domains:

  * Linux kernel
  * user space
  * `java.util.logging` (JUL)
  * log4j

Different tracers expose common features in their own interfaces, but,
from a user's perspective, you still need to target a specific type of
tracer to perform some actions. For example, since both kernel and user
space tracers support named tracepoints (probes manually inserted in
source code), you need to specify which one is concerned when enabling
an event because both domains could have existing events with the same
name.

Some features are not available in all domains. Filtering enabled
events using custom expressions, for example, is currently not
supported in the kernel domain, but support could be added in the
future.
Commit	Line	Data
5e0cbfb0 PP	1	---
	2	id: domain
	3	---
	4
	5	A tracing _domain_ is the official term the LTTng project uses to
	6	designate a tracer category.
	7
c23b8cb1	8	There are currently four known domains:
5e0cbfb0 PP	9
	10	* Linux kernel
	11	* user space
c23b8cb1 PP	12	* `java.util.logging` (JUL)
c23b8cb1 PP	13	* log4j
5e0cbfb0 PP	14
	15	Different tracers expose common features in their own interfaces, but,
	16	from a user's perspective, you still need to target a specific type of
	17	tracer to perform some actions. For example, since both kernel and user
	18	space tracers support named tracepoints (probes manually inserted in
	19	source code), you need to specify which one is concerned when enabling
	20	an event because both domains could have existing events with the same
	21	name.
	22
	23	Some features are not available in all domains. Filtering enabled
	24	events using custom expressions, for example, is currently not
	25	supported in the kernel domain, but support could be added in the
	26	future.