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Bug #937

Babeltrace failure in live mode

Added by Li Liguang about 5 years ago. Updated about 5 years ago.

Status:
New
Priority:
Normal
Assignee:
-
Target version:
-
Start date:
09/10/2015
Due date:
% Done:

0%

Estimated time:

Description

When using LTTng in live mode, with the Babeltrace tool, the output of Babeltrace stalls after a while. The tracing continues, but the output is no longer seen from Babeltrace.The scenario seems to happen mostly under heavy loaded tracing.

lttng version is :
lttng version 2.7.0-pre - Gaia -v2.6.0-rc1-242-g60f7035.

When the failure occurs Babeltrace outputs the following message:

[error] Unexpected end of packet. Either the trace data stream is corrupted or metadata description does not match data layout.
[error] Reading event failed.
[warning] [Context] Cannot open_trace of format lttng-live at path net://localhost/host/localhost/dcsession.
[warning] [Context] cannot open trace "net://localhost/host/localhost/dcsession" for reading.
[error] opening trace "net://localhost/host/localhost/dcsession" for reading.

[error] none of the specified trace paths could be opened.

Sometimes Babeltrace outputs the following message:

[error] get_next_index: error
[error] get_next_index failed

The scenario can easily be reproduces as follows:
1. lttng-relayd d -o /tmp/lttng/live
2.lttng-sessiond --no-kernel --daemonize
3.lttng -n create session --live 1000000 -U net://localhost/
4.lttng enable-channel channel0 -u --buffers-uid -C 1024k -W 1
5.lttng enable-event --userspace --channel channel0 -a
6.lttng start
7../hello ---
>(demo application)
8.babeltrace --clock-date --no-delta -i lttng-live net://localhost/host/localhost/session

This is my demo application:

1 #include <stdio.h>
2 #include "hello-tp.h"
3
4 void test_bp(void)
5 {
6 printf("\r\ncome in bp function for testing\r\n");
7 return;
8 }
9
10 int main(int argc, char* argv[])
11 {
12 int x;
13
14 puts("Hello, World!\nPress Enter to continue...");
15
16 /* The following getchar() call is only placed here for the purpose
17 * of this demonstration, for pausing the application in order for
18 * you to have time to list its events. It's not needed otherwise.
19 /
20 getchar();
21
22 /
A tracepoint() call. Arguments, as defined in hello-tp.tp:
23 *
24 * 1st: provider name (always)
25 * 2nd: tracepoint name (always)
26 * 3rd: my_integer_arg (first user-defined argument)
27 * 4th: my_string_arg (second user-defined argument)
28 *
29 * Notice the provider and tracepoint names are NOT strings;
30 * they are in fact parts of variables created by macros in
31 * hello-tp.h.
32 */
33 for(;;)
34 {
35 // sleep(2);
36 tracepoint(hello_world, my_first_tracepoint, 23, "hi there!");
37
38 for (x = 0; x < argc; ++x) {
39 tracepoint(hello_world, my_first_tracepoint, x, argv[x]);
40 }
41 // test_bp();
42 }
43 puts("Quitting now!");
44
45 // test_bp();
46 tracepoint(hello_world, my_first_tracepoint, x * x, "x^2");
47
48
49
50 return 0;
51 }

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