DTrace Probes

FoundationDB contains many dtrace probes that can be inspected during runtime with tools like bcc and SystemTap. All of them are in the foundationdb provider namespace.

FDB_TRACE_PROBE is simply an alias to the varias DTRACE_PROBE macros.

Probes

Actors

FDB_TRACE_PROBE(actor_create, "actorname")
FDB_TRACE_PROBE(actor_destroy, "actorname")

Get’s called whenever an actor is created or gets destroyed. It provides one argument which is a string and it is the name of the actor.

FDB_TRACE_PROBE(actor_enter, "name", index)
FDB_TRACE_PROBE(actor_exit, "name", index)

Whenever we call into an actor (either directly through a function call or indirectly through a callback) we call actor_enter. Whenever we leave an actor (either because it returns or because it calls into wait) we call actor_exit. The first argument is a string of the name of the actor and the second is an index. -1 means that we entered/exited through in a main function call, otherwise it is a generated index.

Main-Loop

FDB_TRACE_PROBE(run_loop_begin)

Is called whenever the main network loop starts over.

FDB_TRACE_PROBE(run_loop_ready_timers, numTimers)

On each iteration of the run-loop, this indicates how many timers (created through delay or yield) are ready. Its argument is of type int.

FDB_TRACE_PROBE(run_loop_thread_ready, numReady)

On each loop-iteration. The second argument is of type int and it is the number of thread ready processes.

FDB_TRACE_PROBE(run_loop_yield)

Run loop yields.

FDB_TRACE_PROBE(run_loop_tasks_start, queueSize)

FDB_TRACE_PROBE(run_loop_done, queueSize)

One iteration of the run-loop is done. The argument is of type int and is the remaining number of tasks on the ready queue.