SoW-2019-0007-2: Dynamic Snapshot: Triggers send partial event payload with notifications

[lttng-tools.git] / doc / examples / trigger-on-event / README.md

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+# Trigger notification example
+
+## Description
+This example is made-up of three executables.
+
+### `notification-client`
+
+```
+Usage: notification-client TRIGGER_NAME TRIGGER_NAME2 ...
+```
+
+A simple client that subscribes to the notifications emitted by the `TRIGGER_NAME` trigger.
+
+Multiple trigger names can be passed and subscribed to.
+
+
+### `instrumented-app`
+
+An application that emits the `trigger_example:my_event` event every 2 seconds.
+
+### `demo.sh`
+
+This script adds a trigger named `demo_trigger` which emits a notification when
+the user-space `trigger_example:my_event` event occurs.
+
+This script also adds a trigger named `demo_trigger_capture` which emits a
+notification when the user-space `trigger_example:my_event` event occurs and
+provides captured fields if present.
+
+Once the triggers have been setup, the notification-client is launched to print
+all notifications emitted by the `demo_trigger` and `demo_trigger_capture`
+trigger.
+
+## Building
+
+Simply run the included Makefile.
+
+## Running the example
+
+1) Launch a session daemon using:
+        ```
+        $ lttng-sessiond
+        ```
+2) Launch the `demo.sh` script
+3) Launch the `instrumented-app`
+
+The following output should be produced:
+
+```
+$ ./demo.sh
+Registering a notification trigger named "demo_trigger" for the trigger_example:my_event user-space event
+Trigger registered successfully.
+Subscribed to notifications of trigger "demo_trigger"
+[02-14-2020] 18:13:34.779652 - Received notification of event rule trigger "demo_trigger_capture"
+Captured field values:
+  Unsigned int: 0,
+  CAPTURE UNAVAILABE
+[02-14-2020] 18:13:34.779766 - Received notification of event rule trigger "demo_trigger"
+[02-14-2020] 18:13:36.779798 - Received notification of event rule trigger "demo_trigger_capture"
+Captured field values:
+  Unsigned int: 1,
+  CAPTURE UNAVAILABE
+[02-14-2020] 18:13:36.779888 - Received notification of event rule trigger "demo_trigger"
+[02-14-2020] 18:13:38.780234 - Received notification of event rule trigger "demo_trigger_capture"
+Captured field values:
+  Unsigned int: 2,
+  CAPTURE UNAVAILABE
+[02-14-2020] 18:13:38.780514 - Received notification of event rule trigger "demo_trigger"
+[02-14-2020] 18:13:40.780574 - Received notification of event rule trigger "demo_trigger_capture"
+Captured field values:
+  Unsigned int: 3,
+  CAPTURE UNAVAILABE
+[02-14-2020] 18:13:40.780656 - Received notification of event rule trigger "demo_trigger"
+```
+
+```
+$ ./instrumented-app
+[02-14-2020] 18:13:34.779433 - Tracing event "trigger_example:my_event"
+[02-14-2020] 18:13:36.779693 - Tracing event "trigger_example:my_event"
+[02-14-2020] 18:13:38.780010 - Tracing event "trigger_example:my_event"
+[02-14-2020] 18:13:40.780286 - Tracing event "trigger_example:my_event"
+```