doc/examples/trigger-on-event/README.md

   1 # Trigger notification example
   2
   3 ## Description
   4 This example is made-up of three executables.
   5
   6 ### `notification-client`
   7
   8 ```
   9 Usage: notification-client TRIGGER_NAME TRIGGER_NAME2 ...
  10 ```
  11
  12 A simple client that subscribes to the notifications emitted by the `TRIGGER_NAME` trigger.
  13
  14 Multiple trigger names can be passed and subscribed to.
  15
  16
  17 ### `instrumented-app`
  18
  19 An application that emits the `trigger_example:my_event` event every 2 seconds.
  20
  21 ### `demo.sh`
  22
  23 This script adds a trigger named `demo_trigger` which emits a notification when
  24 the user-space `trigger_example:my_event` event occurs.
  25
  26 This script also adds a trigger named `demo_trigger_capture` which emits a
  27 notification when the user-space `trigger_example:my_event` event occurs and
  28 provides captured fields if present.
  29
  30 Once the triggers have been setup, the notification-client is launched to print
  31 all notifications emitted by the `demo_trigger` and `demo_trigger_capture`
  32 trigger.
  33
  34 ## Building
  35
  36 Simply run the included Makefile.
  37
  38 ## Running the example
  39
  40 1) Launch a session daemon using:
  41         ```
  42         $ lttng-sessiond
  43         ```
  44 2) Launch the `demo.sh` script
  45 3) Launch the `instrumented-app`
  46
  47 The following output should be produced:
  48
  49 ```
  50 $ ./demo.sh
  51 Registering a notification trigger named "demo_trigger" for the trigger_example:my_event user-space event
  52 Trigger registered successfully.
  53 Subscribed to notifications of trigger "demo_trigger"
  54 [02-14-2020] 18:13:34.779652 - Received notification of event rule trigger "demo_trigger_capture"
  55 Captured field values:
  56   Unsigned int: 0,
  57   CAPTURE UNAVAILABE
  58 [02-14-2020] 18:13:34.779766 - Received notification of event rule trigger "demo_trigger"
  59 [02-14-2020] 18:13:36.779798 - Received notification of event rule trigger "demo_trigger_capture"
  60 Captured field values:
  61   Unsigned int: 1,
  62   CAPTURE UNAVAILABE
  63 [02-14-2020] 18:13:36.779888 - Received notification of event rule trigger "demo_trigger"
  64 [02-14-2020] 18:13:38.780234 - Received notification of event rule trigger "demo_trigger_capture"
  65 Captured field values:
  66   Unsigned int: 2,
  67   CAPTURE UNAVAILABE
  68 [02-14-2020] 18:13:38.780514 - Received notification of event rule trigger "demo_trigger"
  69 [02-14-2020] 18:13:40.780574 - Received notification of event rule trigger "demo_trigger_capture"
  70 Captured field values:
  71   Unsigned int: 3,
  72   CAPTURE UNAVAILABE
  73 [02-14-2020] 18:13:40.780656 - Received notification of event rule trigger "demo_trigger"
  74 ```
  75
  76 ```
  77 $ ./instrumented-app
  78 [02-14-2020] 18:13:34.779433 - Tracing event "trigger_example:my_event"
  79 [02-14-2020] 18:13:36.779693 - Tracing event "trigger_example:my_event"
  80 [02-14-2020] 18:13:38.780010 - Tracing event "trigger_example:my_event"
  81 [02-14-2020] 18:13:40.780286 - Tracing event "trigger_example:my_event"
  82 ```