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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 | ## Running the example | |
35 | ||
36 | 1) Launch a session daemon using: | |
37 | ``` | |
38 | $ lttng-sessiond | |
39 | ``` | |
40 | 2) Launch the `demo.sh` script | |
41 | 3) Launch the `instrumented-app` | |
42 | ||
43 | The following output should be produced: | |
44 | ||
45 | ``` | |
46 | $ ./demo.sh | |
47 | Registering a notification trigger named "demo_trigger" for the trigger_example:my_event user-space event | |
48 | Trigger registered successfully. | |
49 | Trigger registered successfully. | |
50 | Subscribed to notifications of trigger "demo_trigger_capture" | |
51 | Subscribed to notifications of trigger "demo_trigger" | |
52 | [08-24-2020] 17:20:33.598221 - Received notification of event rule matches trigger "demo_trigger" | |
53 | [08-24-2020] 17:20:33.598855 - Received notification of event rule matches trigger "demo_trigger_capture" | |
54 | Captured field values: | |
55 | Field: iteration Value: [Unsigned int] 0, | |
56 | Field: does_not_exist Value: Capture unavailable, | |
57 | Field: $ctx.vtid Value: [Unsigned int] 2302494, | |
58 | Field: $ctx.procname Value: [String] instrumented-ap. | |
59 | [08-24-2020] 17:20:35.598556 - Received notification of event rule matches trigger "demo_trigger" | |
60 | [08-24-2020] 17:20:35.599293 - Received notification of event rule matches trigger "demo_trigger_capture" | |
61 | Captured field values: | |
62 | Field: iteration Value: [Unsigned int] 1, | |
63 | Field: does_not_exist Value: Capture unavailable, | |
64 | Field: $ctx.vtid Value: [Unsigned int] 2302494, | |
65 | Field: $ctx.procname Value: [String] instrumented-ap. | |
66 | [08-24-2020] 17:20:37.598977 - Received notification of event rule matches trigger "demo_trigger" | |
67 | [08-24-2020] 17:20:37.599676 - Received notification of event rule matches trigger "demo_trigger_capture" | |
68 | Captured field values: | |
69 | Field: iteration Value: [Unsigned int] 2, | |
70 | Field: does_not_exist Value: Capture unavailable, | |
71 | Field: $ctx.vtid Value: [Unsigned int] 2302494, | |
72 | Field: $ctx.procname Value: [String] instrumented-ap. | |
73 | [08-24-2020] 17:20:39.599430 - Received notification of event rule matches trigger "demo_trigger" | |
74 | [08-24-2020] 17:20:39.600178 - Received notification of event rule matches trigger "demo_trigger_capture" | |
75 | Captured field values: | |
76 | Field: iteration Value: [Unsigned int] 3, | |
77 | Field: does_not_exist Value: Capture unavailable, | |
78 | Field: $ctx.vtid Value: [Unsigned int] 2302494, | |
79 | Field: $ctx.procname Value: [String] instrumented-ap. | |
80 | ... | |
81 | ``` | |
82 | ||
83 | ``` | |
84 | $ ./instrumented-app | |
85 | [08-24-2020] 17:20:33.597441 - Tracing event "trigger_example:my_event" | |
86 | [08-24-2020] 17:20:35.597703 - Tracing event "trigger_example:my_event" | |
87 | [08-24-2020] 17:20:37.597997 - Tracing event "trigger_example:my_event" | |
88 | ... | |
89 | ``` | |
90 | ||
91 |