----- On Jul 2, 2020, at 8:45 AM, Jonathan Rajotte
jonathan.rajotte-jul...@efficios.com wrote:
> On Thu, Jul 02, 2020 at 08:38:57AM +0800, zhenyu.ren via lttng-dev wrote:
>> Thanks a lot. I will try single quotes but it may take hours get the result.
>> Yesterday, I enabled the verbose option ,and found the following message "UST
>> app reply event failed. Application died (in add_event_ust_registry() at
>> ust-app.c:5405)" and "UST app notify socket unregister 34 (in
>> ust_app_notify_sock_unregister() at ust-app.c:5562)". In fact ,the socket
>> that
>> Lttng-sessiond send reply to my app return an error with EPIPE. It seems that
>> the pipe breaked.So do you have any hint for that?
>
> From lttng master:
> ret = ustctl_reply_register_event(sock, event_id, ret_code);
> if (ret < 0) {
> if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
> ERR("UST app reply event failed with ret %d", ret);
> } else {
> DBG3("UST app reply event failed. Application died");
> }
> /*
> * No need to wipe the create event since the application socket will
> * get close on error hence cleaning up everything by itself.
> */
> goto error;
> }
>
> EPIPE ifor this socket is considered as an expected scenario.
>
> This normally indicates a short-lived application or that your application
> crashed while lttng-ust and lttng-tools were performing an event registration.
> Considering that the path leading to the ustctl_reply_register_event call is
> preceded by a call fetching information from the same socket
> (ustctl_recv_register_event), I expect this to be a completely normal scenario
> unless you provide evidence that this application under tracing was acting
> normally and had a long lifetime.
In addition, one thing to consider is that if the application is a daemon
process closing all file descriptors, using fork, clone or daemon, then
helper libraries need to be preloaded with the daemon following instructions
in the man-page lttng-ust(3) under section "Using LTTng-UST with daemons".
Failure to preload those libraries in daemons would trigger the observed
scenario: the application hangs up the UST communication socket
and never reconnects.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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