[lttng-dev] Creating custom application

[Mosleh Uddin]

Hello,

Sorry, I should be more specific. I am creating a custom yocto build. I
have seen some examples where systemd is utilized to start the sessiond as
a service. The limitation I have is that I don't want to include the whole
lttng-tools librray in my build. I understand that the sessiond is an
executable, I am just unsure how I could build or get this in my build.
Moving forward from this I could use fork/exec to daemonize which would be
simple.
Is there perhaps a existing recipe?

Regards,
Mosleh

On Tue, Apr 2, 2019 at 6:01 PM Mosleh Uddin <mosleh1235 at gmail.com> wrote:

> 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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