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Bug #972

closed

Babeltrace terminates unexpectedly during lttng-live trace reading

Added by Li Liguang about 9 years ago. Updated about 9 years ago.

Status:
Resolved
Priority:
Low
Assignee:
-
Category:
-
Target version:
-
Start date:
11/04/2015
Due date:
% Done:

100%

Estimated time:

Description

Problem description:
Watching the tracking log on another host by using lttng-relayd and babeltrace as a lttng-live viewer, during live tracing, babeltrace unexpected stops without any error reported.

How can the problem be reproduced:
First execute the following two commands on a Ubuntu host.
1). lttng-relayd -d -o /tmp/lttng/live/
2). lttng-session -d --no-kernel

Then execute the following commands on another Ubuntu host.
3). lttng-relayd -d -o /tmp/lttng/live/
4). lttng-session -d --no-kernel
5). lttng create s1 --live -U net://ip (ip: the address of the first Ubuntu host)
6). lttng enable-event -u -a
7). lttng start
8). ./hello (a test application can be found on LTTng web site: http://lttng.org/docs/#doc-tracing-your-own-user-application)

At last, observe tracking log on the first Ubuntu host.
9). babeltrace --clock-date --no-delta /tmp/lttng/live/localhost/s1-20000107-015309/

About twenty minutes, the babeltrace tracing stops without any error reported.

The debug log is as following:

[04:36:03.081401633] (+0.010076186) localhost hello_world:my_first_tracepoint: { timestamp_begin = 678972918036556, timestamp_end = 678973917652555, content_size = 20768, packet_size = 32768, events_discarded = 0, cpu_id = 0 }, { id = ( "compact" : container = 0 ), v = { compact = { timestamp = 109183534 } } }, { my_string_field = "i'm there", my_integer_field = 3 }
[debug] ctf_pos_get_event offset 20608content_size 20768
[debug] ctf_move_pos test EOF: 20608
[debug] ctf_move_pos after increment: 20608
[debug] ctf_move_pos test EOF: 20608
[debug] ctf_move_pos after increment: 20608
[debug] ctf_move_pos test EOF: 20608
[debug] ctf_move_pos after increment: 20613
[debug] ctf_move_pos test EOF: 20613
[debug] ctf_move_pos after increment: 20613
[debug] ctf_move_pos test EOF: 20613
[debug] ctf_move_pos after increment: 20613
[debug] ctf_move_pos test EOF: 20613
[debug] ctf_move_pos after increment: 20613
[debug] ctf_move_pos test EOF: 20613
[debug] ctf_move_pos after increment: 20640
[debug] ctf_move_pos test EOF: 20640
[debug] ctf_move_pos after increment: 20640
[debug] ctf_move_pos test EOF: 20640
[debug] ctf_move_pos after increment: 20640
[debug] CTF string read i'm there
[debug] ctf_move_pos test EOF: 20640
[debug] ctf_move_pos after increment: 20720
[debug] ctf_move_pos test EOF: 20720
[debug] ctf_move_pos after increment: 20736
[debug] ctf_move_pos test EOF: 20736
[debug] ctf_move_pos after increment: 20768
[04:36:03.091477819] (+0.010076186) localhost hello_world:my_first_tracepoint: { timestamp_begin = 678972918036556, timestamp_end = 678973917652555, content_size = 20768, packet_size = 32768, events_discarded = 0, cpu_id = 0 }, { id = ( "compact" : container = 0 ), v = { compact = { timestamp = 119259720 } } }, { my_string_field = "i'm there", my_integer_field = 3 }
[debug] ctf_packet_seek (before call): 20768
[debug] ctf_packet_seek (after call): -1
[verbose] finished converting. Output written to:
<stdout>

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 #1

Updated by Jonathan Rajotte Julien about 9 years ago

Hi Li

As long as I remember the use of babeltrace on a live trace without the use of a "--input-format lttng-live" argument does not guarantee synchronization of reading thus if babeltrace read an EOF for the trace it exit. As seen in this debug line:

[verbose] finished converting

See https://lttng.org/docs/#doc-lttng-live for proper usage of the live mode.

Also there is some big incoherence in the way you expect live to work.

The proper scenario would be:

First ubuntu host:

lttng-relayd -d -o /tmp/lttng/live/

Starting a sessiond is useless here.

On the second host:

lttng-sessiond -d --no-kernel
lttng create s1 --live -U net://ip (ip: the address of the first Ubuntu host)
lttng enable-event -u -a
lttng start
./hello

No need to start a relayd here since we send data to a remote relayd.

On the first ubuntu host:
First list the available live session for localhost:

babeltrace --clock-date --no-delta -i lttng-live net://localhost

Then hook babeltrace with the full url (opn my tegst it was):
babeltrace -i lttng-live --clock-date --no-delta net://localhost/host/myhostname/s1

Could you make sure to redo your experiment this way and report your finding?

Cheers!

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 #2

Updated by Jonathan Rajotte Julien about 9 years ago

  • Status changed from New to Feedback
  • Priority changed from Normal to Low
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 #3

Updated by Li Liguang about 9 years ago

Hi,

Thanks for the feedback, i didn't understand clearly about the remote live mode at that time.

Follow the steps you provide, this problem no longer appear. Is my error, please close this issue. Thanks.

Regards.

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 #4

Updated by Jonathan Rajotte Julien about 9 years ago

  • Status changed from Feedback to Resolved
  • % Done changed from 0 to 100
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