From: Mathieu Desnoyers
Sent: Tuesday, November 05, 2013 3:20 PM
To: DavidLindström
Cc: [email protected]
Subject: Re: [lttng-dev] Tagging traces with arbitrary data (as in
custommetadata)
------------------------------------------------------------------------------
From: "David Lindström" <[email protected]>
To: [email protected]
Sent: Tuesday, November 5, 2013 9:15:14 AM
Subject: [lttng-dev] Tagging traces with arbitrary data (as in custom
metadata)
Hi, I was wondering if there’s a way to tag a trace with some additional
information. A general example would be to include a description of the current
experiment. One way to do this currently would be to create a custom
lttng-message application with some UST tracepoint and then just log that to a
separate channel, but that would be pretty ugly. It would be much cleaner to
insert extra fields into the metadata stream. Is something like that possible
in current versions of LTTng and/or would it be possible to add it for a future
version?
The CTF metadata has an environment (env {}) section that contains this kind
of information. LTTng already uses it to store the tracer version and some info
about the system. We could eventually add a feature like this, a "tag", that
would be added to the CTF environment information. I would guess that users
would provide this tag on the lttng command line for their session, and it
would be passed to the tracers by sessiond.
Thoughts ?
I have no idea how this would be implemented, I’m only looking at potential
uses. A simple tag field in the env{} section should cover my initial use
cases. I have to wonder though, how much more complicated it would be to allow
multiple named tags? For example, tags.description = ”Some description” instead
of tag = “Some description”?
Also, how would one specify this? As an option to the lttng create command or
as a separate command (lttng set-tag ...)?
Mvh
David Lindström
Thanks,
Mathieu
Mvh
David Lindström
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--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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