doc/streaming-howto.txt

   1 STREAMING
   2 ----------------
   3
   4 [Last updated: 2012-07-17 by David Goulet]
   5
   6 This is a brief howto for network streaming feature of lttng 2.0 toolchain.
   7
   8 See the README file for installation procedure or use the various Linux
   9 distribution packages.
  10
  11 Terminology:
  12
  13         * The "target" is the traced machine (either UST or/and kernel tracer)
  14
  15         * The "remote" is the machine that receives the traces over network
  16         streaming transport layer.
  17
  18 Basics:
  19
  20 Here are the basic concepts of the new streaming component. We use two network
  21 ports for that called _control_ and _data_ respectively defined by default to
  22 5342 and 5343.
  23
  24 The control port is where the commands AND metadata data are sent since this
  25 stream is considered to be the reliable and priority transport channel. The
  26 data port is the stream which transports the tracing raw data.
  27
  28 In order to gather traces from the network, the remote machine MUST have a
  29 lttng-relayd running on it bound to network interfaces remotely reachable by the
  30 target.
  31
  32 [remote] $ lttng-relayd -d
  33 (to daemonize)
  34
  35 [remote] $ lttng-relayd -vvv
  36 (foreground with debug output)
  37
  38 [remote] $ lttng-relayd -C tcp://0.0.0.0:1234 -D tcp://0.0.0.0:5678
  39 (control port set to TCP/1234 and data port to TCP/5678 on all IP addresses)
  40
  41 For now, only TCP is supported on IPv4/IPv6.
  42
  43 Once done, the following examples shows you how to start streaming from the
  44 target machine to the remote host where we just started a lttng relay.
  45
  46 Example 1:
  47 ----------------
  48
  49 Simple and quick network streaming.
  50
  51 1) Create a tracing session that will be streamed over the network for the
  52 specified domain. This session will contain, in our example, syscall events.
  53
  54   # lttng create syscall-session
  55
  56 2) Enable the consumer to send data over the network for the kernel domain.
  57
  58   # lttng enable-consumer --kernel net://<remote_addr>
  59
  60   You can also skip this step and directly use the lttng create command like so:
  61
  62   # lttng create -U net://<remote_addr> syscall-session
  63
  64 3) Set and start the tracing. Nothing new here.
  65
  66   # lttng enable-event -a --syscall -k
  67   # lttng start
  68   (wait and get coffee)
  69   # lttng stop
  70
  71 By default on the relay side, the trace will be written to the lttng-traces/
  72 directory of the relayd user in:
  73
  74   hostname/session-name/kernel/*
  75
  76 The -o option of lttng-relayd allows the user to override the default output
  77 path.
  78
  79 Just run babeltrace or lttng view -t PATH with the previous path.
  80
  81 Example 2:
  82 ----------------
  83
  84 This example uses all possible options to fine grained control the streaming.
  85
  86 1) Again, create a tracing session that will be streamed over the network for
  87 the specified domain.
  88
  89   # lttng create syscall-session
  90
  91 2) Set relayd URIs for the tracing session and kernel domain.
  92
  93 ONLY set the remote relayd URIs (both control and data at the same destination
  94 and using default ports) on the consumer but does not enable the consumer to use
  95 network streaming yet.
  96
  97   # lttng enable-consumer -k -U net://<remote_addr>
  98
  99 You can also set both control and data URIs using -C and -D respectively for
 100 that like so:
 101
 102   # lttng enable-consumer -k -C tcp://<remote_addr> -D tcp://<remote_addr>
 103
 104 3) Enable the consumer previously setup with the relayd URIs.
 105
 106 This enables the previous network destination. From this point on, the consumer
 107 is ready to stream once tracing is started.
 108
 109   # lttng enable-consumer -k --enable
 110
 111 4) Set and start the tracing. Nothing new here.
 112
 113   # lttng enable-event -a --syscall -k
 114   # lttng start
 115   (wait and get coffee)
 116   # lttng stop
 117
 118 Again, run babeltrace as mentioned in the previous example on the relayd side.
 119
 120 For more information, please read the --help options of each command or the man
 121 pages lttng(1) and the lttng-relayd(8)