= babeltrace2-source.ctf.lttng-live(7)
:manpagetype: component class
:revdate: 14 September 2019


== NAME

babeltrace2-source.ctf.lttng-live - Babeltrace 2's LTTng live source
component class


== DESCRIPTION

A Babeltrace~2 compcls:source.ctf.lttng-live message iterator
connects to a local or remote https://lttng.org/[LTTng] relay daemon,
receives the streams of a specific tracing session, and emits
corresponding messages.

----
CTF streams over
LTTng live (TCP)
  |
  |   +--------------------+
  |   | src.ctf.lttng-live |
  '-->|                    |
      |                out @--> Sorted messages of one
      +--------------------+    or more streams
----

More information about LTTng live is available in the
https://lttng.org/docs/#doc-lttng-live[LTTng Documentation].

include::common-see-babeltrace2-intro.txt[]

A compcls:source.ctf.lttng-live component has a single output port: its
message iterator muxes (sorts) the messages from the various CTF data
streams internally.

A compcls:source.ctf.lttng-live message iterator handles the messages of
one, and only one LTTng tracing session. A single LTTng tracing session
can contain one or more traces, depending on the active tracing domains
and the configured user space buffering scheme.

The component connects to an LTTng relay daemon using the param:inputs
parameter. This is an array of exactly one string which is the URL of
the LTTng relay daemon to connect to.

By default, if the remote tracing session name does not exist, the
message iterator returns "try again later". This default mode makes the
message iterator never end: even if the remote tracing session is
destroyed, the message iterator keeps on waiting for a tracing session
with the same name to exist. You can change this behaviour with the
param:session-not-found-action initialization parameter.

NOTE: As of this version, you can only create one message iterator per
compcls:source.ctf.lttng-live component. This is because the LTTng live
protocol accepts at most one client per tracing session per LTTng relay
daemon.


== INITIALIZATION PARAMETERS

param:inputs='URL' vtype:[array of one string]::
    Use 'URL' to connect to the LTTng relay daemon.
+
'URL' is an array of exactly one string of which the format is:
+
--
[verse]
net[4]://__RDHOST__[:__RDPORT__]/host/__TGTHOST__/__SESSION__

'RDHOST'::
    LTTng relay daemon's host name or IP address.

'RDPORT'::
    LTTng relay daemon's listening port.
+
If not specified, the component uses the default port ({defrdport}).

'TGTHOST'::
    Target's host name or IP address.

'SESSION'::
    Name of the LTTng tracing session from which to receive data.
--

param:session-not-found-action=(`continue` | `fail` | `end`) vtype:[optional string]::
    When the message iterator does not find the specified remote tracing
    session ('SESSION' part of the param:inputs parameter), do one of:
+
--
`continue` (default)::
    Keep on trying, returning "try again later" to the downstream user
    until the tracing session exists.
+
With this action, the message iterator never ends, as the LTTng live
protocol cannot currently indicate that a tracing session will never
exist.

`fail`::
    Fail.

`end`::
    End.
--


== PORTS

----
+--------------------+
| src.ctf.lttng-live |
|                    |
|                out @
+--------------------+
----


=== Output

`out`::
    Single output port.


== QUERY OBJECTS

=== `babeltrace.support-info`

See man:babeltrace2-query-babeltrace.support-info(7) to learn more
about this query object.

For a string input which honors the LTTng live URL format (see the
param:inputs parameter), the result object is 0.75.


=== `sessions`

You can query the `sessions` object to get a list of available LTTng
tracing sessions for a given LTTng relay daemon URL.

Parameters:

nlparam:url='URL' vtype:[string]::
    Use 'URL' to connect to the LTTng relay daemon.
+
The format of 'URL' is:
+
--
[verse]
net[4]://__RDHOST__[:__RDPORT__]

'RDHOST'::
    LTTng relay daemon's host name or IP address.

'RDPORT'::
    LTTng relay daemon's listening port.
+
If not specified, the query operation uses the default port
({defrdport}).
--

Result object (array of maps, one element for each available tracing
session):

qres:client-count vtype:[unsigned integer]::
    Current number of LTTng live clients connected to the relay daemon
    to receive data from this tracing session.

qres:session-name vtype:[string]::
    Tracing session's name.

qres:stream-count vtype:[unsigned integer]::
    Current number of CTF streams in this tracing sessions, including
    the metadata streams.

qres:target-hostname vtype:[string]::
    Hostname of the tracing session.
+
This is not necessarily the relay daemon's hostname.

qres:timer-us vtype:[unsigned integer]::
    Tracing session's configured live timer's period (µs)
    (see man:lttng-create(1)).

qres:url vtype:[string]::
    URL to use as the first element of the param:inputs parameter to
    connect to the same LTTng relay daemon and receive data from this
    tracing session.


include::common-footer.txt[]


== SEE ALSO

man:babeltrace2-intro(7),
man:babeltrace2-plugin-ctf(7),
man:lttng-relayd(8),
man:lttng-create(1)
