Mathieu Desnoyers: > * David Goulet ([email protected]) wrote: >> Hi everyone, >> >> We discovered a week ago a "broken guarantee" which is that when a >> session is stopped by either using the lttng command or the API call >> lttng_stop_session the traced data MUST be ready to be read. >> >> However, we don't offer that at all for now for both local storage and >> network streaming. The stop command/call simply does _not_ wait for that >> state. >> >> Here is the proposal to fix this issue before the 2.1 stable release. >> Let's add a new API call (extending it) that probes the session daemon >> for the trace files state (still writing, no more data, closed, ...). >> >> Ex: lttng_data_state(handle) >> >> This will bring a change to the default behavior of the stop command. >> From now on, it will wait by default until the data is available to read >> (for both network and local). This will however be done on the client >> side in order to avoid blocking the session daemon client command sub >> system for an unknown amount of time. >> >> The way I propose we proceed is to use the new API call (mention above) >> on the liblttng-ctl side when a stop is done that requires it to wait. >> Unfortunately, there is no clean way to do that other than an active >> loop polling the session daemon... >> >> The "no wait" use case of the stop command will also be added with a >> lttng_stop_session_no_wait or something like that. >> >> In a nutshell: >> >> (new) lttng_data_state(handle) --> name is NOT final, please chip in for >> ideas! :) > > ideas: > > - lttng_data_pending() > - lttng_data_available()
lttng_data_ready? David > > >> (new) lttng_stop_session_no_wait(session_name) --> naming NOT final. > > lttng_stop_session_no_wait sounds ok to me. > > The rest looks good. Let's see if others find better names ;) > > Thanks, > > Mathieu > >> >> (changes) lttng stop (and lttng_stop_session) will now wait for the data >> to be available so babeltrace could be use right after for instance. A >> --no-wait will be added as well to the UI command. >> >> I would like everyone opinion on that because this is an important issue >> that _MUST_ be fixed in 2.1 stable or at least in the 2.1.x series. >> >> Thanks a lot! >> David >> >> _______________________________________________ >> lttng-dev mailing list >> [email protected] >> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
