[ltt-dev] [RFC UST] Processes model

[Stefan Hajnoczi]

On Tue, Jan 18, 2011 at 11:46 AM, Nils Carlson
<nils.carlson at ericsson.com> wrote:
> Stefan Hajnoczi wrote:
>>
>> On Tue, Jan 18, 2011 at 11:15 AM, Nils Carlson
>> <nils.carlson at ericsson.com> wrote:
>>
>>>
>>> Hi,
>>>
>>> Stefan Hajnoczi wrote:
>>>
>>>>
>>>> On Mon, Jan 17, 2011 at 9:13 PM, David Goulet <david.goulet at polymtl.ca>
>>>> wrote:
>>>>
>>>>>
>>>>> I'm submitting a RFC about a "new daemon model" for UST.
>>>>>
>>>>> This is the *first* draft... so a lot of feedback will be appreciated
>>>>> for
>>>>> improvements and ideas!
>>>>>
>>>>
>>>> At first glance I'm concerned about a root ustd daemon.  One of the
>>>> things I like about LTTng UST is that it's low on administration
>>>> overhead and configuration.  Putting a central service in place that
>>>> mediates access introduces a level of complexity that makes it harder
>>>> for unprivileged users who want to quickly trace something in an app
>>>> they are running or developing.
>>>>
>>>
>>> The central daemon is already in place. I assume your talking about
>>> using the usttrace command?
>>>
>>
>> I don't remember ever running as root or having the daemon get in the
>> way.  It makes sense to have an out-of-process daemon but keeping
>> lightweight ad-hoc usage supported is important.  Especially for
>> userspace tracing, LTTng has a big advantage over SystemTap here due
>> to less headaches installing and configuring the tracing system.
>>
>>
>
> The daemon, ustd or ustconsumerd (renamed in the latest version) can run
> in multiple instances. If you run it as a normal user using the usttrace
> command it will create its socket in a different place than the central
> daemon and the application started by usttrace will connect to your its own
> daemon using that socket. I think this design should be possible to keep
> without too much ado.
>
> Do you ever start applications without using the usttrace command and
> connect
> to them with ustctl?

I haven't used UST in a while so I don't remember exactly how I've
invoked it, sorry.

Stefan