[lttng-dev] babeltrace error when reading traces

[Jérémie Galarneau]

On Fri, Nov 7, 2014 at 9:26 AM, Anand Neeli <anand.neeli at gmail.com> wrote:
> Hi All,
> I'm getting following error when reading traces using babeltrace. I have
> enabled lttng using relayd and created live session.
>
> I get this error till the time app is running. After app exits, babeltrace
> is able to read the traces.
>
> Is there any error in my config? or am i doing anything wrong here?
>
> $>babeltrace
> /var/tmp/lttng-traces/node/mysession-20141107-051543/ust/pid/logtrace-5797-20141107-061325/
>
> [warning] Ill-shapen or missing "/* CTF x.y" header for text-only metadata.
>
> [warning] Unsupported CTF specification version 552137642.32558. Trying
> anyway.
>
> [error] at line 1: token "": syntax error, unexpected $end
>
> [error] Error creating AST
>
> [warning] Unable to open trace metadata for path
> "/var/tmp/lttng-traces/node/mysession-20141107-051543/ust/pid/logtrace-5797-20141107-061325".
>
> [warning] [Context] Cannot open_trace of format ctf at path
> /var/tmp/lttng-traces/vevo_re_node/mysession-20141107-051543/ust/pid/logtrace-5797-20141107-061325.
>
> [warning] [Context] cannot open trace
> "/var/tmp/lttng-traces/node/mysession-20141107-051543/ust/pid/logtrace-5797-20141107-061325"
> from
> /var/tmp/lttng-traces/node/mysession-20141107-051543/ust/pid/logtrace-5797-20141107-061325/
> for reading.
>
> [error] Cannot open any trace for reading.
>
> [error] opening trace
> "/var/tmp/lttng-traces/node/mysession-20141107-051543/ust/pid/logtrace-5797-20141107-061325/"
> for reading.
>
> [error] none of the specified trace paths could be opened.
>
>
>
> The way i'm enabling lttng:
>
>
> sudo -H /usr/bin/lttng-relayd -o /var/tmp/lttng-traces -d
>
> sudo -H /usr/bin/lttng-sessiond --consumerd32-path
> /usr/lib/lttng/libexec/lttng-consumerd --consumerd32-libdir /usr/lib/
> --consumerd64-path /usr/lib64/lttng/libexec/lttng-consumerd
> --consumerd64-libdir /usr/lib64/ -b --no-kernel
>
> sudo -H /usr/bin/lttng create mysession --live 1000000 -U net://$ipaddr
>
> sudo -H /usr/bin/lttng enable-channel mychannel --userspace --buffers-pid -s
> mysession --tracefile-size 8388608 --tracefile-count 8
>
> sudo -H /usr/bin/lttng enable-event --channel mychannel --userspace --all
> --exclude 'ust_libc:*' -s mysession
>
> sudo -H /usr/bin/lttng start
>

It seems you are reading a trace from disk before stopping the tracing
session. This is unsupported since we have no way to guarantee the
trace is readable at all time.
The intended way of consuming a live trace while a session is active
is to connect to the relay daemon using babeltrace's "-i lttng-live"
option.

Assuming the relay daemon and the viewer are running on the same
machine, connecting to the relay daemon will provide you with a list
of available tracing sessions.

babeltrace -i lttng-live net://localhost

You can then connect to a specific session using

babeltrace -i lttng-live net://localhost/my_session

Regards,
Jérémie

>
> Thanks,
>
> Anand Neeli
>
>
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>



-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com