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Re: [tracecompass-dev] How To View Live Traces
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On 2016-03-07 01:36 PM, Michael Steppe wrote:
Ah, I missed the Import button in the LTTng Control view. Unfortunately,
this still didn't work for me. Although I was enabled all UST events (I am
in the process of compiling the kernel modules and figured I would test the
userspace portion a while). When I click the Import button after creating
my session, channel, and enabling all UST events, I get the following error:
'Importing Traces...' has encountered a problem.
The connection to the relayd could not be established. The trace could not
be opened in Live mode.
When I click on the details I get the following:
The connection to the relayd could not be established. The trace cannot be
opened in Live mode.
Error, trace has no metadata.
I have checked the chkconfig values, and relayd is on and I have checked
the init.d service status and it says that relayd is running.
As far as I know, the relayd is not supposed to start automatically. You
mention "chkconfig", I assume you are on Red Hat or CentOS? Do the Red
Hat packages include an init.d script that starts the relayd
automatically? And if so, does it start the correct one that matches
your version of lttng-tools and UST?
Cheers,
Alex
On Mon, Mar 7, 2016 at 12:58 PM, Bernd Hufmann <bernd.hufmann@xxxxxxxxxxxx>
wrote:
You don't need to navigate to the trace. It should be linked automatically
into the Project Explorer view. I just tried it with the following steps:
In the LTTng Control view
- Right mouse-click on Sessions
- Click on context-sensitive menu item "Create Session..."
- Enter session name (optional)
- Click on Live radio button
- Click on OK button.
After that enable relevant events and start the session. Then click on the
import button of the toolbar of LTTng Control view (alternatively right
mouse click on the session in the tree and click on "Import..."). This will
create a link to the trace in the Project Explorer under the "Remote"
tracing project. Also, it will open the trace. The trace name is the
session name.
On my machine, I only enabled the sched_switch event of the Kernel. In my
case the Events Table, Histogram view, Control Flow view is updated. It
works but it seems to be very slow. Then I closed all views besides the
Events Table and it works better.
Please let me know how it goes.
Bernd
On 03/07/2016 12:19 PM, Michael Steppe wrote:
Thank you Bernd. I am running LTTng 2.7 and Trace Compass 1.2.
Unfortunately, I cannot figure out how to open the live trace while it is
running. I start the live trace in the Control view and then click
Import>Tracing>Trace Import and cannot figure out how to navigate to the
path of the live trace, as it is running on "tcp4://127.0.0.1:5342/". Any
ideas how to do this?
On Mon, Mar 7, 2016 at 11:21 AM, Bernd Hufmann <bernd.hufmann@xxxxxxxxxxxx
wrote:
Hi Michael
Live trace reading within Trace Compass is supported but it is still
rudimentary and needs some improvements. When implementing the support for
live trace reading in Trace Compass the use cases were not fully clear. We
still need some user feedback to improve upon the current implementation.
If you have any suggestions please let us know (on the mailing list or on
bugzilla). Due to other priorities we are not currently working on this.
However, we would be glad to review any contributions and improvements.
What is currently possible
----------------------------------
It is possible to create a live session using the LTTng Control view (as
you already realized). One thing to know is that the lttng-relayd and Trace
Compass has to run on the same host. It is not possible to use a
lttng-relayd running on a separate node for live trace reading.
After configuring the live session from Trace Compass (using the Control
view) you can import the trace from the control view. This will link the
trace into the tracing project where you can open the trace. Trace Compass
will discover new events using the lttng-relayd and the following views
will be updated when new data arrives:
- Events table
- Histogram view
- Statistics view
- Views that are using a state system are updated (e.g. Control Flow view)
Note that Trace Compass will read the data from the disk written by
lttng-relayd. It is not requesting the trace events directly from the
lttng-relayd. That's why lttng-relayd and Trace Compass have to run at the
same host.
The last time I tried it I realized some issues. I used with LTTng 2.7
and Trace Compass 1.2 at that time. I opened 2 bugs to track the issues and
improvements [1] and [2]. Note that traced system, lttng-relayd and Trace
Compass were running at the same machine in my test.
Known limitations
-----------------------
- Tracing the system (kernel and/UST) on the same node than lttng-relayd
and Trace Compass is performant
- Live updating of several views is very slow
- It's only possible to stream one trace at a time, e.g. just LTTng
Kernel or one UST application with per-uid buffers for tracing.
Best Regards
Bernd
[1] https://bugs.eclipse.org/bugs/show_bug.cgi?id=486728
[2] https://bugs.eclipse.org/bugs/show_bug.cgi?id=486727
On 03/04/2016 11:39 AM, Michael Steppe wrote:
Hello,
I have looked in your documentation at
<http://archive.eclipse.org/tracecompass/doc/org.eclipse.tracecompass.doc.user/LTTng-Tracer-Control.html>
http://archive.eclipse.org/tracecompass/doc/org.eclipse.tracecompass.doc.user/LTTng-Tracer-Control.html
and have been able to create and run a live trace (both through the command
line and through Eclipse's control plugin). What I cannot figure out is how
to view this live trace in Eclipse as it is happening. I am able to open
the trace after stopping and destroying it, but would like to see events
streaming in. Is this even possible?
Thanks!
Michael
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