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5e0cbfb0 PP |
1 | --- |
2 | id: sending-trace-data-over-the-network | |
3 | --- | |
4 | ||
5 | The possibility of sending trace data over the network comes as a | |
6 | built-in feature of LTTng-tools. For this to be possible, an LTTng | |
7 | _relay daemon_ must be executed and listening on the machine where | |
8 | trace data is to be received, and the user must create a tracing | |
9 | session using appropriate options to forward trace data to the remote | |
10 | relay daemon. | |
11 | ||
12 | The relay daemon listens on two different TCP ports: one for control | |
13 | information and the other for actual trace data. | |
14 | ||
15 | Starting the relay daemon on the remote machine is as easy as: | |
16 | ||
17 | <pre class="term"> | |
18 | lttng-relayd | |
19 | </pre> | |
20 | ||
21 | This will make it listen to its default ports: 5342 for control and | |
22 | 5343 for trace data. The `--control-port` and `--data-port` options may | |
23 | be used to specify different ports. | |
24 | ||
25 | Traces written by `lttng-relayd` are written to | |
26 | <code>~/lttng-traces/<em>hostname</em>/<em>session</em></code> by | |
27 | default, where <code><em>hostname</em></code> is the host name of the | |
28 | traced (monitored) system and <code><em>session</em></code> is the | |
29 | tracing session name. Use the `--output` option to write trace data | |
30 | outside `~/lttng-traces`. | |
31 | ||
32 | On the sending side, a tracing session must be created using the | |
33 | `lttng` tool with the `--set-url` option to connect to the distant | |
34 | relay daemon: | |
35 | ||
36 | <pre class="term"> | |
37 | lttng create my-session --set-url net://distant-host | |
38 | </pre> | |
39 | ||
40 | The URL format is described in the output of `lttng create --help`. | |
41 | The above example will use the default ports; the `--ctrl-url` and | |
42 | `--data-url` options may be used to set the control and data URLs | |
43 | individually. | |
44 | ||
45 | Once this basic setup is completed and the connection is established, | |
46 | you may use the `lttng` tool on the target machine as usual; everything | |
47 | you do will be transparently forwarded to the remote machine if needed. | |
48 | For example, a parameter changing the maximum size of trace files will | |
49 | have an effect on the distant relay daemon actually writing the trace. |