* David Goulet ([email protected]) wrote: > > > On 11-01-31 02:06 PM, Mathieu Desnoyers wrote: >> * David Goulet ([email protected]) wrote: >>> Everything about a per-user ltt-sessiond will be added to the RFC! >>> >>> Comments below. >>> >>> On 11-01-31 12:10 PM, Mathieu Desnoyers wrote: >>>> * David Goulet ([email protected]) wrote: >>>>> This unique identifier SHOULD be a unique string consisting of the >>>>> username, a >>>>> session name and the number of already created session plus one. The last >>>>> number makes sure that the ID is unique in the ltt-sessiond context. In >>>>> the >>>>> implementation, a simple number could be use for performance purpose >>>>> instead of >>>>> comparing string at each iteration. >>>>> >>>>> Ex: Username - "dave", Session name - "mysession", Num. sessions - fifth >>>>> one >>>>> --> ID: dave.mysession-5 >>>> >>>> We will run into problems across reboots: session IDs might be reused, thus >>>> trying to overwrite older traces. Other ideas, possibly including UUID, >>>> would be >>>> welcome. >>> >>> Across reboot... I don't see the problem reusing IDs... The only problem >>> to overwrite older traces is if the session ID is used in the trace path >>> on the disk which is not the case. >> >> Then what do you propose using as directory name to hold the trace on disk ? >> Using the session name would seem natural. > > Yep, absolutely for the first level directory but the trace file path > should be quite different. We talked about something like this the other > day : > > $sessionID/ > $appname-$date-$time-$PID > > having $sessionID the above proposition : dave.session_name-5
Well, that's where I see a problem: if we gather a trace on a system from user "dave", with the same session name, the incremented "unique" number is only unique as long as we don't restart ltt-sessiond. So if we reboot the system, the same tracing session name will be reused, rendering it non-unique. I would really like drtrace to be able to work without requiring the user to explicitely specify a session name. This is why using a UUID (truly unique ID) would make sense as default session identifier. When the user specify the session name, I see no point in trying to fixup the clash with a postfix: we could simply return an error, saying that there is already a trace in there. > > The $time is a bit useless but makes the trace path "unique" since the > case of having the same date, appname and PID can occur. Sure, I agree on this one. Using "$appname-$date-$time-$PID" as subdirectory to hold the per-application traces makes sense. Thanks, Mathieu > I'm actually quite open for better suggestion :) > > I'll make sure the rest of that email is taking into account for the > next version! > > Thanks > David > > -- > David Goulet > LTTng project, DORSAL Lab. > > PGP/GPG : 1024D/16BD8563 > BE3C 672B 9331 9796 291A 14C6 4AF7 C14B 16BD 8563 -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com _______________________________________________ ltt-dev mailing list [email protected] http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
