lttng-dev.lists.lttng.org archive mirror
 help / color / mirror / Atom feed
From: Eqbal via lttng-dev <lttng-dev@lists.lttng.org>
To: Jonathan Rajotte-Julien <jonathan.rajotte-julien@efficios.com>
Cc: lttng-dev@lists.lttng.org
Subject: Re: [lttng-dev] lttng live event loss with babeltrace2
Date: Mon, 10 May 2021 17:35:41 -0700	[thread overview]
Message-ID: <CAPj=Wkgmf1xGq0H4ka5B5KyXipGReFMuQo4=aMK5NS6fPVL3oA@mail.gmail.com> (raw)
In-Reply-To: <20210507180532.GA1227214@joraj-alpa>


[-- Attachment #1.1: Type: text/plain, Size: 2528 bytes --]

Hi,

I ran my test with the new changes and it seems to improve the lossiness
but not eliminate it. For example it seems in the hello world example that
if the application exits too quickly after emitting the tracepoint, we
might still lose some events in the consumer even though they are present
in the relayd output folder. I don't quite understand why that is. Would
love some explanations on the various timing windows where we have a
potential to lose the events on the consumer side.

Thanks,
Eqbal

On Fri, May 7, 2021 at 11:05 AM Jonathan Rajotte-Julien <
jonathan.rajotte-julien@efficios.com> wrote:

> Hi,
>
> See
> https://github.com/lttng/lttng-tools/commit/c876d657fb08a91ca7c907b92f1b7604aee664ee
> .
>
> We would appreciate your feedback on this if possible based on your use
> case.
>
> Cheers
>
> On Mon, May 03, 2021 at 05:05:10PM -0700, Eqbal via lttng-dev wrote:
> > Hi,
> >
> > I have a lttng live session trace consumer application using
> libbabeltrace2
> > where I create a graph to consume lttng live session traces and output to
> > another sink. I am running the graph in a loop at some polling interval
> as
> > long as I get BT_GRAPH_RUN_STATUS_AGAIN status. What I am noticing is
> that
> > if my polling interval is large enough I tend to lose either all or some
> of
> > the events. I experimented with various polling intervals and it seems if
> > the polling interval is less than *DELAYUS *from "lttng-create
> > --live=DELAYUS" option then I am able to get all the events, otherwise I
> > tend to lose events.
> >
> > Here are the steps I follow:
> > 1. start session daemon and relay daemon
> > 2. create a live session (with default delay of 1s), enable events and
> start
> > 3. Start my application (hello world example from lttng docs)
> > 4. Start the consumer application built using libbabeltrace that connects
> > to the live session
> >
> > I noticed that the events are actually persisted in the ~/lttng-traces by
> > the relay daemon, but it does not reach babeltrace consumer application.
> I
> > have noticed the same behavior with babeltrace2 cli.
> >
> > I would like to understand what is the reason for such behavior and if
> > playing with the polling interval in relation to the DELAYUS value is the
> > right thing to do.
> >
> > Thanks,
> > Eqbal
>
> > _______________________________________________
> > lttng-dev mailing list
> > lttng-dev@lists.lttng.org
> > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>
>
> --
> Jonathan Rajotte-Julien
> EfficiOS
>

[-- Attachment #1.2: Type: text/html, Size: 3448 bytes --]

[-- Attachment #2: Type: text/plain, Size: 156 bytes --]

_______________________________________________
lttng-dev mailing list
lttng-dev@lists.lttng.org
https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

  reply	other threads:[~2021-05-11  0:35 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-04  0:05 Eqbal via lttng-dev
2021-05-04 13:16 ` Jonathan Rajotte-Julien via lttng-dev
2021-05-04 14:44 ` Jonathan Rajotte-Julien via lttng-dev
2021-05-07 18:05 ` Jonathan Rajotte-Julien via lttng-dev
2021-05-11  0:35   ` Eqbal via lttng-dev [this message]
2021-05-11  1:14     ` Jonathan Rajotte-Julien via lttng-dev

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAPj=Wkgmf1xGq0H4ka5B5KyXipGReFMuQo4=aMK5NS6fPVL3oA@mail.gmail.com' \
    --to=lttng-dev@lists.lttng.org \
    --cc=eqbalzee@gmail.com \
    --cc=jonathan.rajotte-julien@efficios.com \
    --subject='Re: [lttng-dev] lttng live event loss with babeltrace2' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).