Merge branch 'handle-no-lttng-python-module-found' into 'master'

Improve handling and reporting of LTTng Python module status

See merge request micro-ROS/ros_tracing/ros2_tracing!132

tracetools_trace/tracetools_trace/tools/lttng.py

@@ -14,6 +14,8 @@
 
 """Interface for tracing with LTTng."""
 
+import sys
+
 from typing import List
 from typing import Optional
 
@@ -21,8 +23,18 @@ try:
     from . import lttng_impl
 
     _lttng = lttng_impl
+
+    # Check lttng module version
+    from distutils.version import StrictVersion
+    current_version = _lttng.get_version()
+    LTTNG_MIN_VERSION = '2.10.7'
+    if current_version is None or current_version < StrictVersion(LTTNG_MIN_VERSION):
+        print(
+            f'lttng module version >={LTTNG_MIN_VERSION} required, found {str(current_version)}',
+            file=sys.stderr,
+        )
 except ImportError:
-    # Fall back on empty functions
+    # Fall back on stub functions so that this still passes linter checks
     from . import lttng_stub
 
     _lttng = lttng_stub

tracetools_trace/tracetools_trace/tools/lttng_impl.py

@@ -14,8 +14,11 @@
 
 """Implementation of the interface for tracing with LTTng."""
 
+from distutils.version import StrictVersion
+import re
 from typing import List
 from typing import Optional
+from typing import Union
 
 import lttng
 
@@ -26,6 +29,23 @@ from .path import DEFAULT_BASE_PATH
 from .path import get_full_session_path
 
 
+def get_version() -> Union[StrictVersion, None]:
+    """
+    Get the version of the lttng module.
+
+    The module does not have a __version__ attribute, but the version is mentioned in its __doc__,
+    and seems to be written in a consistent way across versions.
+
+    :return: the version as a StrictVersion object, or `None` if it cannot be extracted
+    """
+    doc_lines = lttng.__doc__.split('\n')
+    first_line = list(filter(None, doc_lines))[0]
+    version_string = first_line.split(' ')[1]
+    if not re.compile(r'^[0-9]+\.[0-9]+\.[0-9]+$').match(version_string):
+        return None
+    return StrictVersion(version_string)
+
+
 def setup(
     session_name: str,
     base_path: str = DEFAULT_BASE_PATH,

tracetools_trace/tracetools_trace/tools/lttng_stub.py

@@ -15,17 +15,20 @@
 """Stub version of the interface for tracing with LTTng."""
 
 
+ERROR_MESSAGE = 'lttng module not found, but still tried to use it'
+
+
 def setup(*args, **kwargs) -> None:
-    pass
+    raise RuntimeError(ERROR_MESSAGE)
 
 
 def start(*args, **kwargs) -> None:
-    pass
+    raise RuntimeError(ERROR_MESSAGE)
 
 
 def stop(*args, **kwargs) -> None:
-    pass
+    raise RuntimeError(ERROR_MESSAGE)
 
 
 def destroy(*args, **kwargs) -> None:
-    pass
+    raise RuntimeError(ERROR_MESSAGE)