LTTng » LTTng-tools

If you create a session which streams its data, it is possible to specify a non-sensical arrangement where the control and data ports are the same (this is not possible on the receiving end since lttng-relayd will fail to launch when the ports are the same):

$ sudo -H lttng -vvv create rsession -U net://131.132.32.77:5342:5342
DEBUG3: URI string: net://131.132.32.77:5342:5342 [in uri_parse() at uri.c:253]
DEBUG2: IP address resolved to 131.132.32.77 [in set_ip_address() at uri.c:132]
DEBUG3: URI dtype: 1, proto: 1, host: 131.132.32.77, subdir: , ctrl: 5342, data: 5342 [in uri_parse() at uri.c:467]
DEBUG1: LSM cmd type : 8 [in send_session_msg() at lttng-ctl.c:261]
Session rsession created.
Traces will be written in net://131.132.32.77:5342:5342
DEBUG1: Init config session in /root [in config_init() at conf.c:294]
$ sudo -H lttng -vvv enable-event -k sched_switch
DEBUG2: Config file path found: /root [in get_session_name() at utils.c:50]
DEBUG1: Session name found: rsession [in get_session_name() at utils.c:51]
DEBUG1: Enabling kernel event sched_switch for channel channel0 [in enable_events() at commands/enable_events.c:458]
DEBUG1: LSM cmd type : 6 [in send_session_msg() at lttng-ctl.c:261]
kernel event sched_switch created in channel channel0
$ sudo -H lttng -vvv start
DEBUG2: Config file path found: /root [in get_session_name() at utils.c:50]
DEBUG1: Session name found: rsession [in get_session_name() at utils.c:51]
DEBUG1: Starting tracing for session rsession [in start_tracing() at commands/start.c:81]
DEBUG1: LSM cmd type : 16 [in send_session_msg() at lttng-ctl.c:261]
Tracing started for session rsession
$ sudo -H lttng -vvv stop
DEBUG2: Config file path found: /root [in get_session_name() at utils.c:50]
DEBUG1: Session name found: rsession [in get_session_name() at utils.c:51]
DEBUG1: LSM cmd type : 17 [in send_session_msg() at lttng-ctl.c:261]
DEBUG1: LSM cmd type : 24 [in send_session_msg() at lttng-ctl.c:261]
Waiting for data availability
Tracing stopped for session rsession
$ sudo -H lttng -vvv destroy
DEBUG2: Config file path found: /root [in get_session_name() at utils.c:50]
DEBUG1: Session name found: rsession [in get_session_name() at utils.c:51]
DEBUG1: LSM cmd type : 9 [in send_session_msg() at lttng-ctl.c:261]
Session rsession destroyed
DEBUG1: Removing /root/.lttngrc
 [in config_destroy() at conf.c:151]

At the receiving end, the only symptom is this occasional message (once the trace is started; it reflects the arrival of data at the control port):

Error: Received unknown command (0)