Re: [lttng-dev] Usage example of libbabeltrace (babeltrace2) to read CTF traces from a GUI

[Steven Rostedt <rostedt@goodmis.org>]

[ Adding linux-trace-devel too ]

On Tue, 15 Jun 2021 11:13:41 -0400
Philippe Proulx <pproulx@efficios.com> wrote:

> On Mon, Jun 14, 2021 at 4:01 PM Mathieu Desnoyers via lttng-dev
> <lttng-dev@lists.lttng.org> wrote:
> >
> > Hi Philippe, Hi Jeremie,
> >
> > Steven is interested to use libbabeltrace as a CTF trace reader in the KernelShark
> > project. It's a GUI which shows Linux kernel traces.
> >
> > He notices that most of the documented usage examples of the libbabeltrace API
> > focus on use-cases where a custom trace format is converted into CTF.
> >
> > I know that the babeltrace2 program is the main user of libbabeltrace at this
> > point, and that it reads CTF as source.
> >
> > For using libbabeltrace as CTF reader for a GUI, what would be the best examples
> > to look at as starting point ? Perhaps the babeltrace2 binary, or just adapt a
> > smaller example program and change the custom trace format source to "ctf.fs" ?
> > Or anything else ?  
> 
> Hello,
> 
> Unfortunately, the Babeltrace 2 C API documentation [1] doesn't offer a
> graph building example at the moment.
> 
> Therefore, indeed, the "best" example would be the babeltrace2(1) CLI
> (see `src/cli`), although I understand that it's a very generic example
> which can be overwhelming to explore.
> 
> However, note that instead of instantiating an existing sink component
> class (as found in a plugin), you'll want to make your own sink
> component class to get access to each event message while also
> controlling the graph operations. Using
> bt_graph_add_simple_sink_component() [2] would be a good start.
> 
> I can cook a minimal working example in the following days.

That would be great, thanks!

-- Steve

> 
> Phil
> 
> [1]: https://babeltrace.org/docs/v2.0/libbabeltrace2/
> [2]: https://babeltrace.org/docs/v2.0/libbabeltrace2/group__api-graph.html#gaa8432f03a967d01b764fb1bc959c8e89
> 
> >
> > Thanks,
> >
> > Mathieu
> >
> > --
> > Mathieu Desnoyers
> > EfficiOS Inc.
> > http://www.efficios.com
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