GSoC Project | Basic Support for Trace Compass

[Sebastian Huber]

On 04/06/2019 19:26, Ravindra Kumar Meena wrote:
> Hi Sebastian,
>
> I am in regular touch with Babeltrace community to figure out the 
> solution for conversion of trace data into CTF. I came to the 
> conclusion that current version 1.5.6 of Babeltrace does not have a 
> feature to convert live trace stream into CTF(we already had a 
> discussion about it). However, this feature is currently available in 
> Babeltrace 2.0(master branch) but it is currently in pre-stage.
>
> The approach they shared is that after post-processing phase to 
> convert traces from some existing format to CTF we have to create a 
> Babeltrace 2 source plugin which reads our trace format into the 
> Babeltrace 2 intermediate representation by using the APIs exposed to 
> plugins by Babeltrace 2. Babeltrace 2 has a generic CTF sink which can 
> serialize the resulting trace intermediate representation into CTF.
>
> The conversation I had between them in May is: 
> https://lists.lttng.org/pipermail/lttng-dev/2019-May/028944.html
>
> and this months conversation is: 
> https://lists.lttng.org/pipermail/lttng-dev/2019-June/029022.html
>
> Please have a look at the above thread. The community is very helpful 
> they have even shared a decoder(source plugin) example(you can see 
> them in the thread itself) which is necessary for whatever is produced 
> as trace output to convert into CTF. I will have a look at it.

Thanks for the summary. The Babeltrace 2 source plugin look like the way 
to go.

>
> I also came to know that Trace Compass does not support live 
> traces. It is made for post-mortem analyses, so it works only on 
> complete trace. They briefly supported live traces a few years back, 
> but that made the code much more complicated, so this support was 
> dropped. TraceCompass is not made for trace monitoring!

Hm, interesting. This limitation is not really visible from the 
marketing sites.

>
> You can view the whole conversation here(I did this during application 
> period): 
> https://lists.lttng.org/pipermail/lttng-dev/2019-March/028677.html

In the e-mail a session rotation is mentioned. This doesn't sound that 
bad. At the moment this is not really important. We need the basics first.

>
> So, in my point of view, we should stick with the post-processing 
> method. We should store the traces in the disk and then convert it to CTF.

I would try to concentrate on a Babeltrace 2 source plugin. If it works 
we should try to upstream it to:

https://github.com/efficios/babeltrace/tree/master/plugins

Alternatively, you can try to write the converter using support from 
barectf.

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
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E-Mail  : sebastian.huber at embedded-brains.de
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