[lttng-dev] babeltrace2: reading metadata + events from a single CTF file

[Dave Bort]

Hello! I'm adding CTF-compatible tracing to a custom/experimental OS and
have a question:

Can babeltrace2 read from a single CTF output file that contains both the
metadata stream and the binary trace streams?

My little trace system would like to bundle everything related to a trace
into a single file, making it easier to pass around (since there's not much
filesystem/network support yet). The CTF spec provides a way to embed the
metadata stream in the same bitstream as the data streams, but
https://babeltrace.org/docs/v2.0/man7/babeltrace2-source.ctf.fs.7/ says
that the `metadata` file needs to be separate. I see that LTTng manages
trace output as a collection of files, with a separate `metadata` file.

I'd rather avoid writing a custom tool to find and extract the metadata
stream from the full stream before passing the data on to babeltrace2 or
TraceCompass, but so far it looks like I may need to.

Would it be appropriate to add support for this
to babeltrace2-source.ctf.fs? Or would this warrant a new source.ctf
plugin? If I'm going to write some new code to handle this situation, I may
as well try to add it to the project.

Thank you! I'm really looking forward to benefiting from the
CTF/babeltrace/LTTng/TraceCompass work you've all done over the years. :)

--Dave Bort
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