[lttng-dev] [bug]session create failed

[Jérémie Galarneau]

Hi Lingyu,

See below for an explanation of the error messages you get.

On Tue, Mar 18, 2014 at 12:25 PM, Lingyu Zhu <lynuszhu at gmail.com> wrote:
> Hello,
> Sorry for being away a few days. My thesis opening proposal is hiting the
> deadline, which happens to be same date for GSoC. Now I can be fully devoted
> to lttng and compose my GSoC proposal.
>
> Anyway, I may have found a bug.I'm not very sure. Here is my log:
>
> ===================================================
> [lynus at slave1 ~]$lttng create
> Spawning a session daemon
> Session auto-20140319-081547 created.
> Traces will be written in /home/lynus/lttng-traces/auto-20140319-081547
> [lynus at slave1 ~]$ lttng enable-event page_block -k
> Error: Event page_block: Tracing the kernel requires a root lttng-sessiond
> daemon, as well as "tracing" group membership or root user ID for the lttng
> client. (channel channel0, session auto-20140319-081547)
> Warning: Some command(s) went wrong

As the error message indicates, only a root session daemon can
interact with the kernel tracer. To allow non-root users the ability
to perform kernel tracing, users can interact with the kernel tracer
via the session daemon, but only if they are a member of the "tracing"
group. This is expected.

Note that a session daemon was launched and is now running as user
"lynus". This session daemon is waiting for Java applications to
register on port 5345, by default.

> [lynus at slave1 ~]$ lttng destroy
> Session auto-20140319-081547 destroyed
> [lynus at slave1 ~]$ sudo su -
> [sudo] password for lynus:
> root at slave1:~# lttng create
> Spawning a session daemon

Now, a second session daemon, running as "root", is launched.

> Warning: No tracing group detected
> Session auto-20140319-081615 created.
> Traces will be written in /root/lttng-traces/auto-20140319-081615
> PERROR [4774/4882]: bind inet: Address already in use (in
> lttcomm_bind_inet_sock() at inet.c:109)
> Warning: An other session daemon is using this JUL port. JUL support will be
> deactivated not interfering with the tracing.

This indicates that the second session daemon could not bind to the
default Java (JUL) registration port.

One way to work around this issue is to either ensure you have only
one session daemon running, or to specify a different jul-tcp-port by
launching the session daemon manually and using its "--jul-tcp-port"
option. See LTTNG-SESSIOND(8).

This only affects JUL application tracing; the userspace and kernel
tracing features will work as expected.

Let me know if you need more help,
Jérémie.

> root at slave1:~# lttng create
> Session auto-20140319-081620 created.
> Traces will be written in /root/lttng-traces/auto-20140319-081620
> root at slave1:~#
> [END] 2014/3/19 0:04:31
> ======================================================
>
> These command is issued right after my machine is booted. And if I directly
> switch to root and create a seesion, everything is normal. So I guess I may
> have come across a bug.
> Any comment?
>
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>



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