Error out if trace already exists unless 'append trace' option is used

Signed-off-by: Christophe Bedard <christophe.bedard@apex.ai>

tracetools_launch/tracetools_launch/action.py

@@ -109,6 +109,7 @@ def __init__(
         session_name: SomeSubstitutionsType,
         append_timestamp: bool = False,
         base_path: Optional[SomeSubstitutionsType] = None,
+        append_trace: bool = False,
         events_ust: Iterable[SomeSubstitutionsType] = names.DEFAULT_EVENTS_ROS,
         events_kernel: Iterable[SomeSubstitutionsType] = [],
         context_fields:
@@ -135,6 +136,8 @@ def __init__(
         :param append_timestamp: whether to append timestamp to the session name
         :param base_path: the path to the base directory in which to create the session directory,
             or `None` for default
+        :param append_trace: whether to append to the trace directory if it already exists,
+            otherwise an error is reported
         :param events_ust: the list of ROS UST events to enable
         :param events_kernel: the list of kernel events to enable
         :param context_fields: the names of context fields to enable
@@ -152,6 +155,7 @@ def __init__(
         self.__session_name = normalize_to_list_of_substitutions(session_name)
         self.__base_path = base_path \
             if base_path is None else normalize_to_list_of_substitutions(base_path)
+        self.__append_trace = append_trace
         self.__trace_directory = None
         self.__events_ust = [normalize_to_list_of_substitutions(x) for x in events_ust]
         self.__events_kernel = [normalize_to_list_of_substitutions(x) for x in events_kernel]
@@ -174,6 +178,10 @@ def session_name(self):
     def base_path(self):
         return self.__base_path
 
+    @property
+    def append_trace(self):
+        return self.__append_trace
+
     @property
     def trace_directory(self):
         return self.__trace_directory
@@ -272,6 +280,10 @@ def parse(cls, entity: Entity, parser: Parser):
         base_path = entity.get_attr('base-path', optional=True)
         if base_path:
             kwargs['base_path'] = parser.parse_substitution(base_path)
+        append_trace = entity.get_attr(
+            'append-trace', data_type=bool, optional=True, can_be_str=False)
+        if append_trace is not None:
+            kwargs['append_trace'] = append_trace
         # Make sure to handle empty strings and replace with empty lists,
         # otherwise an empty string enables all events
         events_ust = entity.get_attr('events-ust', optional=True)
@@ -402,6 +414,7 @@ def _setup(self) -> bool:
             self.__trace_directory = lttng.lttng_init(
                 session_name=self.__session_name,
                 base_path=self.__base_path,
+                append_trace=self.__append_trace,
                 ros_events=self.__events_ust,
                 kernel_events=self.__events_kernel,
                 context_fields=self.__context_fields,
@@ -436,6 +449,7 @@ def __repr__(self):
             'Trace('
             f'session_name={self.__session_name}, '
             f'base_path={self.__base_path}, '
+            f'append_trace={self.__append_trace}, '
             f'trace_directory={self.__trace_directory}, '
             f'events_ust={self.__events_ust}, '
             f'events_kernel={self.__events_kernel}, '

tracetools_trace/tracetools_trace/tools/args.py

@@ -76,3 +76,6 @@ def add_arguments(parser: argparse.ArgumentParser) -> None:
     parser.add_argument(
         '-l', '--list', dest='list', action='store_true',
         help='display lists of enabled events and context names (default: %(default)s)')
+    parser.add_argument(
+        '-a', '--append-trace', dest='append_trace', action='store_true',
+        help='append to trace if it already exists, otherwise error out (default: %(default)s)')

tracetools_trace/tracetools_trace/tools/lttng_impl.py

@@ -68,6 +68,7 @@ def setup(
     *,
     session_name: str,
     base_path: str,
+    append_trace: bool = False,
     ros_events: Union[List[str], Set[str]] = DEFAULT_EVENTS_ROS,
     kernel_events: Union[List[str], Set[str]] = [],
     context_fields: Union[List[str], Set[str], Dict[str, List[str]]] = DEFAULT_CONTEXT,
@@ -89,6 +90,8 @@ def setup(
     :param session_name: the name of the session
     :param base_path: the path to the directory in which to create the tracing session directory,
         which will be created if needed
+    :param append_trace: whether to append to the trace directory if it already exists, otherwise
+        an error is reported
     :param ros_events: list of ROS events to enable
     :param kernel_events: list of kernel events to enable
     :param context_fields: the names of context fields to enable
@@ -106,6 +109,11 @@ def setup(
     # Validate parameters
     if not session_name:
         raise RuntimeError('empty session name')
+    # Resolve full tracing directory path
+    full_path = os.path.join(base_path, session_name)
+    if os.path.isdir(full_path) and not append_trace:
+        raise RuntimeError(
+            f'trace directory already exists, use the append option to append to it: {full_path}')
 
     # Check if there is a session daemon running
     if lttng.session_daemon_alive() == 0:
@@ -179,9 +187,8 @@ def setup(
         channel_kernel.attr.output = lttng.EVENT_MMAP
         events_list_kernel = _create_events(kernel_events)
 
-    # Resolve full tracing directory path and create session
+    # Create session
     # LTTng will create the parent directories if needed
-    full_path = os.path.join(base_path, session_name)
     _create_session(session_name, full_path)
 
     # Handles, channels, events

tracetools_trace/tracetools_trace/trace.py

@@ -33,6 +33,7 @@ def init(
     *,
     session_name: str,
     base_path: Optional[str],
+    append_trace: bool,
     ros_events: List[str],
     kernel_events: List[str],
     context_fields: List[str],
@@ -46,6 +47,8 @@ def init(
     :param session_name: the name of the session
     :param base_path: the path to the directory in which to create the tracing session directory,
         or `None` for default
+    :param append_trace: whether to append to the trace directory if it already exists, otherwise
+        an error is reported
     :param ros_events: list of ROS events to enable
     :param kernel_events: list of kernel events to enable
     :param context_fields: list of context fields to enable
@@ -84,6 +87,7 @@ def init(
     trace_directory = lttng.lttng_init(
         session_name=session_name,
         base_path=base_path,
+        append_trace=append_trace,
         ros_events=ros_events,
         kernel_events=kernel_events,
         context_fields=context_fields,
@@ -137,6 +141,7 @@ def trace(args: argparse.Namespace) -> int:
         if not init(
             session_name=args.session_name,
             base_path=args.path,
+            append_trace=args.append_trace,
             ros_events=args.events_ust,
             kernel_events=args.events_kernel,
             context_fields=args.context_fields,