Files
scylladb/tracing
Vlad Zolotarov 37da6f53f8 tracing: fix a session "duration" semantics
A session's "duration" should be a time it took to
handle a request, which is a time till response to a user.
In other words - till a consistency level is reached.

Before this patch is was a time that takes a complete
handling of a request, which is the time it takes to handle
all replicas and not only those required to reach a CL.

This patch fixes this situation by extending the trace_state's state
values to 3 states: inactive, foreground and background.

A primary session may be in 3 states:
  - "inactive": between the creation and a begin() call.
  - "foreground": after a begin() call and before a
    stop_foreground_and_write() call.
  - "background": after a stop_foreground_and_write() call and till the
    state object is destroyed.

- Traces are not allowed while state is in an "inactive" state.
- The time the primary session was in a "foreground" state is the time
  reported as a session's "duration".
- Traces that have arrived during the "background" state will be recorded
  as usual but their "elapsed" time will be greater or equal to the
  session's "duration".

Secondary sessions may only be in an "inactive" or in a "foreground"
states.

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
2016-08-16 12:32:34 +03:00
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