README-LIVE

As of LTTng v2.4, we can now process traces while they are being recorded
(called live-tracing). LTTngtop can read live traces either in the ncurses GUI
or in text mode.

In order to use this feature, start by creating a live session with at least
the events and contexts required for LTTngtop (see the manpage for that).  A
simple script to do the basic setup is available in
utils/create-live-session.sh

Once the session is created, you can list the sessions established on the
relay with :
$ lttngtop -r net://relaydhostname

And attach to a session with 
$ lttngtop -r net://relaydhostname/host/<hostname/<session-name>

A few seconds later, you should begin to see your live trace being displayed in
lttngtop gui.
To use the textdump feature, use the -t (and see --help for more options). You
can also use the new lttngtoptrace provided by lttngtop which does all the setup
for a live trace in textdump on localhost.


EXPERIMENTAL :
In order to use the (beta) MMAP live tracing features of LttngTop, you need these
branches :

git clone -b lttngtop-live git://git.dorsal.polymtl.ca/~jdesfossez/lttng-tools
git clone -b lttngtop-live git://git.dorsal.polymtl.ca/~jdesfossez/babeltrace

The only difference between these branches and the master branch is that they
export an additional library that is used by lttngtop to do live tracing.

You have to compile and install lttng-tools before babeltrace since there are
dependencies on the library exposed by this special lttng-tools in babeltrace
for live mmap buffer consuming.

Then you can compile and use the live branch of LttngTop :
git clone -b live git://git.lttng.org/lttngtop.git

Once everything is installed, you can start as root lttng-sessiond and use
lttngtop (as root or from a user part of the "tracing" group).

Note: if lttng-sessiond has been used to record a trace before starting
lttngtop (normal lttng use-case), you need to restart it because it
automatically spawned a consumer that prevents lttngtop from registering its
own consumer. The same applies when you finish using lttngtop, you need to
restart the lttng-sessiond daemon to allow others to record traces again. This
is a know problem of integration that will be fixed.