<font size=2 face="sans-serif">Hi,</font>
<br>
<br><font size=2 face="sans-serif">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>
<br>
<br><font size=2 color=#ff0041 face="Calibri">************************************************</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>
<br><font size=1 face="Arial">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>
<br>
<br><font size=2 face="sans-serif">Please see the below code snippet
how we are using the lttng calls to handle our requirement</font>
<br><font size=2 face="sans-serif"><b>creation of session:</b></font>
<br><font size=2 face="sans-serif"> lttng
create s1 --snapshot -o /pramfs/telog</font>
<br><font size=2 face="sans-serif"> lttng
enable-channel ch1 -u --buffers-uid --subbuf-size 4096 --num-subbuf 16</font>
<br><font size=2 face="sans-serif"> #
Enable default events</font>
<br><font size=2 face="sans-serif"> lttng
enable-event -u -c ch1 --loglevel TRACE_INFO '*'</font>
<br>
<br><font size=2 face="sans-serif">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>
<br>
<br><font size=2 face="sans-serif">lttng_sessions[0].path contains</font><font size=2 color=blue face="sans-serif">
/pramfs/telog</font>
<br><font size=2 face="sans-serif">myrm is a function pointer which cleans
the directory and returns 770 permissions to that particular snapshot path.</font>
<br>
<br><font size=2 face="sans-serif"> if (ted_ss_reboot
== SS_RB_CONF) {</font>
<br><font size=2 face="sans-serif">
/* Only read snapshot from last reboot once */</font>
<br><font size=2 face="sans-serif">
ted_ss_reboot = SS_RB_DONE;</font>
<br><font size=2 face="sans-serif">
extra = FCORRELATE;</font>
<br><font size=2 face="sans-serif"> } else {</font>
<br><font size=2 face="sans-serif">
/* Remove all previous snapshots from output folder</font>
<br><font size=2 face="sans-serif">
* This way filesystem will not be flooded by snapshots</font>
<br><font size=2 face="sans-serif">
* taken every time user reads the log. OBS, All dirs
under</font>
<br><font size=2 face="sans-serif">
* path will be deleted.</font>
<br><font size=2 face="sans-serif">
*/</font>
<br><font size=2 face="sans-serif">
if (nftw(lttng_sessions[0].path, myrm, FOPEN_MAX, FTW_DEPTH)
< 0) {</font>
<br><font size=2 face="sans-serif">
ERR("Failed to clean path,
%s", lttng_sessions[0].path);</font>
<br><font size=2 face="sans-serif">
goto send_rsp;</font>
<br><font size=2 face="sans-serif">
}</font>
<br><font size=2 face="sans-serif"> }</font>
<br>
<br><font size=2 face="sans-serif"> /*</font>
<br><font size=2 face="sans-serif"> *
Take a snapshot of lttng buffers for a given session</font>
<br><font size=2 face="sans-serif"> */</font>
<br><font size=2 face="sans-serif"> /* Create
a output handle */</font>
<br><font size=2 face="sans-serif"> 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>
<br><font size=2 face="sans-serif">
ERR("lttng_snapshot_output_create failed");</font>
<br><font size=2 face="sans-serif">
ret = -1;</font>
<br><font size=2 face="sans-serif">
goto send_rsp;</font>
<br><font size=2 face="sans-serif"> }</font>
<br>
<br><font size=2 face="sans-serif"> /* Take
a snapshot, output path used is same as configured for the session */</font>
<br><font size=2 face="sans-serif"> 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>
<br><font size=2 face="sans-serif"> if (ret
< 0) {</font>
<br><font size=2 face="sans-serif">
ERR("lttng_snapshot_record failed, ses:%s, %s",</font>
<br><font size=2 face="sans-serif">
lttng_sessions[0].name, lttng_strerror(ret));</font>
<br><font size=2 face="sans-serif">
ret = -1;</font>
<br><font size=2 face="sans-serif">
goto send_rsp;</font>
<br><font size=2 face="sans-serif"> }</font>
<br>
<br>
<br><font size=2 face="sans-serif"> lttng_snapshot_output_destroy(lttng_out);</font>
<br>
<br><font size=2 face="sans-serif"> /*</font>
<br><font size=2 face="sans-serif"> *
snapshot folder created by root lttng-sessiond and all its</font>
<br><font size=2 face="sans-serif"> *
subfolders have permissions set to 770, meaning non-privileged</font>
<br><font size=2 face="sans-serif"> *
user cant read/write from/to that folder. A regular user should</font>
<br><font size=2 face="sans-serif"> *
be able to read traces generated by root sessiond.</font>
<br><font size=2 face="sans-serif"> *
Changing permissions to this file tree.</font>
<br><font size=2 face="sans-serif"> */</font>
<br><font size=2 face="sans-serif"> nftw(lttng_sessions[0].path,
mychmod, FOPEN_MAX, FTW_DEPTH);<br>
</font>
<br><font size=2 face="sans-serif">babeltrace --clock-date --clock-force-correlate
/pramfs/telog</font>
<br><font size=2 face="sans-serif">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>
<br>
<br>
<br>
<br><font size=2 face="sans-serif"><br>
Thanks & Regards<br>
Venkata Ranganadh Kantimahanthi<br>
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