[lttng-dev] Creating custom application

[Mosleh Uddin]

Hi,

That makes complete sense. I was more curious about the sessiond
executable. I'm guessing this is something I will have to create along with
my build?

Regards,
Mosleh

On Tue, Apr 2, 2019 at 5:18 PM Jonathan Rajotte-Julien <
jonathan.rajotte-julien at efficios.com> wrote:

> On Tue, Apr 02, 2019 at 04:54:00PM -0400, Mosleh Uddin wrote:
> > Hello,
> >
> > Could you give me some more insight into spawning my own sessiond? Sorry
> > I'm not completely clear on the topic.
> > Thank you for all your assistance.
>
> Normally lttng-sessiond is treated as a "server/service/daemon" (think http
> server as apache) and is *normally* launched as a daemon
> (systemd/sysVinit) at
> boot time.
>
> Managing manually the lifetime of a lttng-sessiond process is done the
> same way
> as any other process. You can manage it via the command line
> (./lttng-sessiond), via a
> service manager (systemd/upstart etc.) or with a custom service manager (a
> python script/c etc.).
>
> You could spawn a lttng-sessiond from your application with the appropriate
> parameters set to isolate it if you need. LTTNG_HOME is an important one.
> The
> output directory also can be manipulated. See man lttng-sessiond for more
> details. You will need to manage the process or leave it to a system
> administrator and only active tracing when a sessiond is present for
> example.
>
> Cheers
>
> >
> > Regards,
> > Mosleh
> >
> > On Wed, Mar 27, 2019 at 1:52 PM Jonathan Rajotte-Julien <
> > jonathan.rajotte-julien at efficios.com> wrote:
> >
> > > Hi Mosleh,
> > >
> > > On Wed, Mar 27, 2019 at 12:09:54PM -0400, Mosleh Uddin wrote:
> > > > Hello,
> > > >
> > > > Thank you for the quick response. I was able to use the
> documentation you
> > > > provided to start a session and get tracepoint list. I do have some
> > > > follow-up questions:
> > > >
> > > > 1) I needed to create a session daemon before executing my custom
> > > > application. In the API I did see functionality to see if a daemon is
> > > > active, however, it is possible to spawn a session daemon in my
> custom
> > > app?
> > >
> > > liblttng-ctl does not expose a lttng-sessiond spawning function since
> by
> > > definition it is a daemon executable (think apache,mysql etc.), you
> will
> > > have to
> > > use system/popen/exec.. to spawn the lttng-sessiond process etc. if you
> > > want to
> > > control its lifetime using your custom application.
> > >
> > > >
> > > > 2) I am able to get a list of active traces lttng can see in
> userspace, I
> > > > enable all the traces and start tracing. The traces however seem to
> not
> > > be
> > > > written anywhere on my filesystem. Do I have to specify a location?
> Or
> > > am I
> > > > missing something? My current flow is:
> > >
> > > Please refer to the create command. If outputting locally you will
> need to
> > > pass
> > > a "file://...." url to lttng_create_session.
> > >
> > > You can check on the result for each steps using "lttng list" and
> "lttng
> > > list
> > > <session_name>" as you go to troubleshot your setup script.
> > >
> > > While debugging you can also start the lttng-sessiond in verbose mode
> to
> > > understand what is going on.
> > >
> > > Also note that you could also use the lttng "load" api if the session
> you
> > > are
> > > trying to load is "static" and always the same. You would only need to
> > > ship an
> > > xml file with your application.
> > >
> > > Cheers
> > >
> > > >
> > > >    - Creating a session
> > > >    - Specifying the domain
> > > >    - Creating a handle
> > > >    - Creating a channel (with default attributes)
> > > >    - Enabling the channel
> > > >    - Enabling event (for all traces)
> > > >    - Start tracing
> > > >
> > > > Thanks again for all the assistance.
> > > >
> > > > Regards,
> > > > Mosleh
> > > >
> > > > On Tue, Mar 26, 2019 at 11:29 AM Jonathan Rajotte-Julien <
> > > > jonathan.rajotte-julien at efficios.com> wrote:
> > > >
> > >
>
> --
> Jonathan Rajotte-Julien
> EfficiOS
>
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