Merge branch '72-setup-lttng-session-daemon' into 'master'

Start LTTng session daemon if there isn't one

Closes #72

See merge request micro-ROS/ros_tracing/ros2_tracing!155

.gitlab-ci.yml

@@ -23,7 +23,6 @@ tracing_enabled:
   image: $BASE_IMAGE_ID:$DISTRO
   script:
     - lttng --version && apt list lttng-tools liblttng-ust-dev python3-lttng python3-babeltrace
-    - lttng-sessiond --daemonize
     - colcon build --symlink-install --event-handlers console_cohesion+ --packages-up-to $PACKAGES_LIST
     - . install/local_setup.sh
     - ./build/tracetools/status

tracetools_trace/tracetools_trace/tools/lttng_impl.py

@@ -16,6 +16,7 @@
 
 from distutils.version import StrictVersion
 import re
+import subprocess
 from typing import List
 from typing import Optional
 from typing import Set
@@ -74,6 +75,13 @@ def setup(
     :param channel_name_kernel: the kernel channel name
     :return: the full path to the trace directory
     """
+    # Check if there is a session daemon running
+    if lttng.session_daemon_alive() == 0:
+        # Otherwise spawn one without doing any error checks
+        subprocess.run(
+            ['lttng-sessiond', '--daemonize'],
+        )
+
     # Convert lists to sets
     if not isinstance(ros_events, set):
         ros_events = set(ros_events)