<font size=2 face="sans-serif">Hi,</font>
<br>
<br><font size=2 face="sans-serif">I have reproduced the issue with babeltrace
-v option . </font>
<br>
<br><font size=2 face="sans-serif"><br>
<br>
Thanks & Regards<br>
Venkata Ranganadh Kantimahanthi<br>
</font>
<br><font size=1 color=#800080 face="sans-serif">----- Forwarded by Venkata
Kantimahanthi/HYD/TCS on 02/24/2015 03:02 PM -----</font>
<br>
<br><font size=1 color=#5f5f5f face="sans-serif">From:
</font><font size=1 face="sans-serif">Venkata Kantimahanthi
<venkata.kantimahanthi@tcs.com></font>
<br><font size=1 color=#5f5f5f face="sans-serif">To:
</font><font size=1 face="sans-serif">lttng-dev@lists.lttng.org</font>
<br><font size=1 color=#5f5f5f face="sans-serif">Date:
</font><font size=1 face="sans-serif">02/18/2015 02:29 PM</font>
<br><font size=1 color=#5f5f5f face="sans-serif">Subject:
</font><font size=1 face="sans-serif">[lttng-dev]
Error is thrown when continously using babeltrace</font>
<br>
<hr noshade>
<br>
<br>
<br><font size=2 face="sans-serif">Hi,</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
We are using babeltrace 1.2.4 and LTTng Trace Control 2.5.3. Continously
giving babeltrace is throwing this error. I am actually getting this
while reading a snapshot session . I have given continously babeltrace
and path to read the traces . Then I am getting this error.</font><font size=3>
<br>
</font><font size=2 color=#ff0041 face="Calibri"><br>
************************************************</font><font size=1 color=#ff0041 face="Arial">
</font><font size=2 color=#ff0041 face="Calibri"><br>
[error] Unexpected end of packet. Either the trace data stream is corrupted
or metadata description does not match data layout.</font><font size=1 color=#ff0041 face="Arial">
</font><font size=2 color=#ff0041 face="Calibri"><br>
[error] Reading event failed.</font><font size=1 color=#ff0041 face="Arial">
</font><font size=2 color=#ff0041 face="Calibri"><br>
Error printing trace.</font><font size=1 color=#ff0041 face="Arial"> <br>
</font><font size=2 color=#ff0041 face="Calibri"><br>
************************************************</font><font size=1 color=#ff0041 face="Arial">
</font><font size=1 face="Arial"><br>
As you said previously "</font><font size=2 face="Arial"><b>The corrupted
stream probably can't be handled by Babeltrace anymore at that point.</b></font><font size=1 face="Arial">"
</font><font size=3><br>
</font><font size=2 face="sans-serif"><br>
Please see the below code snippet how we are using the lttng calls
to handle our requirement</font><font size=3> </font><font size=2 face="sans-serif"><b><br>
creation of session:</b></font><font size=3> </font><font size=2 face="sans-serif"><br>
lttng create s1 --snapshot -o /pramfs/telog</font><font size=3>
</font><font size=2 face="sans-serif"><br>
lttng enable-channel ch1 -u --buffers-uid
--subbuf-size 4096 --num-subbuf 16</font><font size=3> </font><font size=2 face="sans-serif"><br>
# Enable default events</font><font size=3>
</font><font size=2 face="sans-serif"><br>
lttng enable-event -u -c ch1 --loglevel
TRACE_INFO '*'</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
After succesful creation of the session we are able to read the traces
using babeltrace successfully. But we have written a wrappers for using
lttng API calls in such a way to meet our requirement which is reading
only traces inside the buffer at that instant by writing into a file by
removing previously created snapshots.</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
lttng_sessions[0].path contains</font><font size=2 color=blue face="sans-serif">
/pramfs/telog</font><font size=3> </font><font size=2 face="sans-serif"><br>
myrm is a function pointer which cleans the directory and returns 770 permissions
to that particular snapshot path.</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
if (ted_ss_reboot == SS_RB_CONF) {</font><font size=3>
</font><font size=2 face="sans-serif"><br>
/* Only read snapshot
from last reboot once */</font><font size=3> </font><font size=2 face="sans-serif"><br>
ted_ss_reboot =
SS_RB_DONE;</font><font size=3> </font><font size=2 face="sans-serif"><br>
extra = FCORRELATE;</font><font size=3>
</font><font size=2 face="sans-serif"><br>
} else {</font><font size=3> </font><font size=2 face="sans-serif"><br>
/* Remove all previous
snapshots from output folder</font><font size=3> </font><font size=2 face="sans-serif"><br>
* This way filesystem
will not be flooded by snapshots</font><font size=3> </font><font size=2 face="sans-serif"><br>
* taken every
time user reads the log. OBS, All dirs under</font><font size=3> </font><font size=2 face="sans-serif"><br>
* path will be
deleted.</font><font size=3> </font><font size=2 face="sans-serif"><br>
*/</font><font size=3>
</font><font size=2 face="sans-serif"><br>
if (nftw(lttng_sessions[0].path,
myrm, FOPEN_MAX, FTW_DEPTH) < 0) {</font><font size=3> </font><font size=2 face="sans-serif"><br>
ERR("Failed to clean path, %s", lttng_sessions[0].path);</font><font size=3>
</font><font size=2 face="sans-serif"><br>
goto send_rsp;</font><font size=3> </font><font size=2 face="sans-serif"><br>
}</font><font size=3>
</font><font size=2 face="sans-serif"><br>
}</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
/*</font><font size=3> </font><font size=2 face="sans-serif"><br>
* Take a snapshot of lttng buffers for
a given session</font><font size=3> </font><font size=2 face="sans-serif"><br>
*/</font><font size=3> </font><font size=2 face="sans-serif"><br>
/* Create a output handle */</font><font size=3>
</font><font size=2 face="sans-serif"><br>
if ((lttng_out = </font><font size=2 color=blue face="sans-serif">lttng_snapshot_output_create</font><font size=2 face="sans-serif">())
== NULL) {</font><font size=3> </font><font size=2 face="sans-serif"><br>
ERR("lttng_snapshot_output_create
failed");</font><font size=3> </font><font size=2 face="sans-serif"><br>
ret = -1;</font><font size=3>
</font><font size=2 face="sans-serif"><br>
goto send_rsp;</font><font size=3>
</font><font size=2 face="sans-serif"><br>
}</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
/* Take a snapshot, output path used is same
as configured for the session */</font><font size=3> </font><font size=2 face="sans-serif"><br>
ret =</font><font size=2 color=blue face="sans-serif">
lttng_snapshot_record</font><font size=2 face="sans-serif">(lttng_sessions[0].name,
lttng_out, 0);</font><font size=3> </font><font size=2 face="sans-serif"><br>
if (ret < 0) {</font><font size=3> </font><font size=2 face="sans-serif"><br>
ERR("lttng_snapshot_record
failed, ses:%s, %s",</font><font size=3> </font><font size=2 face="sans-serif"><br>
lttng_sessions[0].name,
lttng_strerror(ret));</font><font size=3> </font><font size=2 face="sans-serif"><br>
ret = -1;</font><font size=3>
</font><font size=2 face="sans-serif"><br>
goto send_rsp;</font><font size=3>
</font><font size=2 face="sans-serif"><br>
}</font><font size=3> <br>
<br>
</font><font size=2 face="sans-serif"><br>
lttng_snapshot_output_destroy(lttng_out);</font><font size=3>
<br>
</font><font size=2 face="sans-serif"><br>
/*</font><font size=3> </font><font size=2 face="sans-serif"><br>
* snapshot folder created by root lttng-sessiond
and all its</font><font size=3> </font><font size=2 face="sans-serif"><br>
* subfolders have permissions set to 770,
meaning non-privileged</font><font size=3> </font><font size=2 face="sans-serif"><br>
* user cant read/write from/to that folder.
A regular user should</font><font size=3> </font><font size=2 face="sans-serif"><br>
* be able to read traces generated by root
sessiond.</font><font size=3> </font><font size=2 face="sans-serif"><br>
* Changing permissions to this file tree.</font><font size=3>
</font><font size=2 face="sans-serif"><br>
*/</font><font size=3> </font><font size=2 face="sans-serif"><br>
nftw(lttng_sessions[0].path, mychmod, FOPEN_MAX,
FTW_DEPTH);</font><font size=3><br>
</font><font size=2 face="sans-serif"><br>
babeltrace --clock-date --clock-force-correlate /pramfs/telog</font><font size=3>
</font><font size=2 face="sans-serif"><br>
which was giving the logs which we were expecting but if we keep this process
repeatedly above mentioned error was coming. I am sharing the log file
(there te log read is the wrapper call for above process which I mentioned).Please
tell if any other logs were required.</font><font size=3> <br>
<br>
<br>
</font><font size=2 face="sans-serif"><br>
<br>
Thanks & Regards<br>
Venkata Ranganadh Kantimahanthi</font>
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