projects / lttngtop.git / blame
| Commit | Line | Data |
|---|---|---|
| 3e06508b JD |
1 | As of LTTng v2.4, we can now process traces while they are being recorded |
| 2 | (called live-tracing). LTTngtop can read live traces either in the ncurses GUI | |
| 3 | or in text mode. | |
| 4 | ||
| 5 | In order to use this feature, start by creating a live session with at least | |
| 6 | the events and contexts required for LTTngtop (see the manpage for that). A | |
| 7 | simple script to do the basic setup is available in | |
| 8 | utils/create-live-session.sh | |
| 9 | ||
| 10 | Once the session is created, you can list the sessions established on the | |
| 11 | relay with : | |
| 12 | $ lttngtop -r net://relaydhostname | |
| 13 | ||
| 14 | And attach to a session with | |
| 15 | $ lttngtop -r net://relaydhostname/host/<hostname/<session-name> | |
| 16 | ||
| 17 | A few seconds later, you should begin to see your live trace being displayed in | |
| 18 | lttngtop gui. | |
| 19 | To use the textdump feature, use the -t (and see --help for more options). You | |
| 20 | can also use the new lttngtrace provided by lttngtop which does all the setup | |
| 21 | for a live trace in textdump on localhost. | |
| 22 | ||
| 23 | ||
| 24 | EXPERIMENTAL : | |
| 25 | In order to use the (beta) MMAP live tracing features of LttngTop, you need these | |
| ce56380f JD |
26 | branches : |
| 27 | ||
| 28 | git clone -b lttngtop-live git://git.dorsal.polymtl.ca/~jdesfossez/lttng-tools | |
| 29 | git clone -b lttngtop-live git://git.dorsal.polymtl.ca/~jdesfossez/babeltrace | |
| 30 | ||
| 31 | The only difference between these branches and the master branch is that they | |
| 32 | export an additional library that is used by lttngtop to do live tracing. | |
| 33 | ||
| 34 | You have to compile and install lttng-tools before babeltrace since there are | |
| 35 | dependencies on the library exposed by this special lttng-tools in babeltrace | |
| 36 | for live mmap buffer consuming. | |
| 37 | ||
| 38 | Then you can compile and use the live branch of LttngTop : | |
| 39 | git clone -b live git://git.lttng.org/lttngtop.git | |
| 62895477 JD |
40 | |
| 41 | Once everything is installed, you can start as root lttng-sessiond and use | |
| 42 | lttngtop (as root or from a user part of the "tracing" group). | |
| 43 | ||
| 44 | Note: if lttng-sessiond has been used to record a trace before starting | |
| 45 | lttngtop (normal lttng use-case), you need to restart it because it | |
| 46 | automatically spawned a consumer that prevents lttngtop from registering its | |
| 47 | own consumer. The same applies when you finish using lttngtop, you need to | |
| 48 | restart the lttng-sessiond daemon to allow others to record traces again. This | |
| 49 | is a know problem of integration that will be fixed. |