Re: [linuxtools-dev] LTTng question

[Mathieu Desnoyers <compudj@xxxxxxxxxxxxxxxxxx>]

* William Bourque (william.bourque@xxxxxxxxxx) wrote:
> 
> Mathieu Desnoyers wrote:
> > * William Bourque (william.bourque@xxxxxxxxxx) wrote:
> >> Xavier RAYNAUD wrote:
> > 
> > [...]
> > 
> >>> I guess I've compiled a wrong version of LTTv application ?
> >>> Which one should I use instead ?
> >>
> >> Hi,
> >>
> >> The help files and the instruction are (already?) a bit outdated, as
> >> well as the sample trace given with the plugin. The traces currently
> >> given with the plugin are no longer compatible with the reading code.
> >> The traces should have been changed already, we will make sure to push
> >> new sample traces today (and to remove the old one). You could also
> >> record one if you have installed the latest Lttng kernel patches.
> >>
> >> Also, make sure to use the latest version of the Lttv C library (you
> >> better use the one at
> >> http://git.dorsal.polymtl.ca/?p=liblttngtrace.git;a=summary  for now,
> >> some changes are not yet been pushed to the main tree).
> >>
> >> Sorry about that, we kind of forgot about these.
> >>
> >>
> >>
> >> To tell you the exact technical details, what's happen is that our
> >> Eclipse plugin use some JNI code to load the C library that handle
> >> parsing and/or moving in the traces. It's the library that is giving you
> >> the warnings and debug information you see.
> >> The library itself is part of the Lttv application and is developped by
> >> another open source project (lttng.org) not related to linuxtools or
> >> Eclipse. The problem that this team recently decide to change their
> >> trace format, so our old trace are no longer supported by their library.
> >> We had already planned to support multiple trace version at the same
> >> time but it's not ready yet so for now we decide to stick with their
> >> latest version. We are currently working with the Lttng.org team so they
> >> add what we need in their library to support multiple trace format,
> >> hopefully it should be ready for the next release of linuxtools.
> > 
> > Hi William,
> > 
> > You should probably create your own "compatibility list" which you post
> > on a website so your users (and yourself) remember which versions fit
> > together in the future. Saying "use the latest version" is vague and
> > does not tell much when someone read a mailing list archive one month in
> > the future.
> 
> Hi,
> 
> You are right and it's already planned to have it for the official
> release of the Eclipse Lttng plugin in linuxtools.
> It's quite hard to do for now, however, as we are playing with
> developpement versions of everything (TMF, Eclipse Lttng and JNI hooks
> in Lttv). The APIs are not yet fixed so "compatible versions" change on
> a weekly basis, it is just not possible to keep track of all changes for
> now.
> "Latest of everything" is the best answer we can give for now,
> especially since a lot of these things have not official versionning out
> of the SVN timestamp.

Then you may want to give svn version number snapshots of where things
were compatible, even in a not-so-official version table somewhre on a
website. The LTTng tracer APIs have been changing a lot in the past
years, and keeping a compatibility list is, I think, the only thing that
helped users keeping up. Please don't do the same mistakes that were
done with the earlier LTT versions, where finding compatible tracer/tool
versions had to result from heroic efforts.

Thanks,

Mathieu

> 
> - William
> 
> > 
> > Thanks,
> > 
> > Mathieu
> > 
> > 
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-- 
Mathieu Desnoyers
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