contents/understanding-lttng/core-concepts/domain.md

   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
   8 There are currently four known domains:
   9
  10   * Linux kernel
  11   * user space
  12   * `java.util.logging` (JUL)
  13   * log4j
  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.