Allow EventHandlers to declare list of required events

tracetools_analysis/tracetools_analysis/processor/__init__.py

@@ -121,8 +121,9 @@ class EventHandler(Dependant):
 
         :param handler_map: the mapping from event name to handling method
         """
-        assert handler_map is not None and len(handler_map) > 0, \
+        assert handler_map is None or len(handler_map) > 0, \
             f'empty map: {self.__class__.__name__}'
+        assert all(required_name in handler_map.keys() for required_name in self.required_events())
         self._handler_map = handler_map
         self.processor = None
 
@@ -136,6 +137,16 @@ class EventHandler(Dependant):
         """Get the data model."""
         return None
 
+    @staticmethod
+    def required_events() -> List[str]:
+        """
+        Get the list of events required by this EventHandler.
+
+        Without these events, the EventHandler would be invalid/useless. Inheriting classes can
+        decide not to declare that they require specific events.
+        """
+        return []
+
     def register_processor(self, processor: 'Processor') -> None:
         """Register processor with this `EventHandler` so that it can query other handlers."""
         self.processor = processor

tracetools_analysis/tracetools_analysis/processor/cpu_time.py

@@ -15,6 +15,7 @@
 """Module for CPU time events processing."""
 
 from typing import Dict
+from typing import List
 
 from tracetools_read import get_field
 
@@ -51,6 +52,12 @@ class CpuTimeHandler(EventHandler):
         # cpu_id -> start timestamp of the running thread
         self._cpu_start: Dict[int, int] = {}
 
+    @staticmethod
+    def required_events() -> List[str]:
+        return [
+            'sched_switch',
+        ]
+
     @property
     def data(self) -> CpuTimeDataModel:
         return self._data_model

tracetools_analysis/tracetools_analysis/processor/memory_usage.py

@@ -15,6 +15,7 @@
 """Module for memory usage events processing."""
 
 from typing import Dict
+from typing import List
 
 from tracetools_read import get_field
 
@@ -96,6 +97,17 @@ class UserspaceMemoryUsageHandler(MemoryUsageHandler):
         # (used to know keep track of the memory size allocated at a given pointer)
         self._memory: Dict[int, int] = {}
 
+    @staticmethod
+    def required_events() -> List[str]:
+        return [
+            'lttng_ust_libc:malloc',
+            'lttng_ust_libc:calloc',
+            'lttng_ust_libc:realloc',
+            'lttng_ust_libc:free',
+            'lttng_ust_libc:memalign',
+            'lttng_ust_libc:posix_memalign',
+        ]
+
     def _handle_malloc(
         self, event: Dict, metadata: EventMetadata
     ) -> None:
@@ -200,6 +212,13 @@ class KernelMemoryUsageHandler(MemoryUsageHandler):
             **kwargs,
         )
 
+    @staticmethod
+    def required_events() -> List[str]:
+        return [
+            'kmem_mm_page_alloc',
+            'kmem_mm_page_free',
+        ]
+
     def _handle_malloc(
         self, event: Dict, metadata: EventMetadata
     ) -> None:

tracetools_analysis/tracetools_analysis/processor/profile.py

@@ -86,6 +86,14 @@ class ProfileHandler(EventHandler):
         #        ]
         self._current_funcs: Dict[int, List[List[Union[str, int]]]] = defaultdict(list)
 
+    @staticmethod
+    def required_events() -> List[str]:
+        return [
+            'lttng_ust_cyg_profile_fast:func_entry',
+            'lttng_ust_cyg_profile_fast:func_exit',
+            'sched_switch',
+        ]
+
     @staticmethod
     def addr_to_int(addr: Union[int, str]) -> int:
         """Transform an address into an `int` if it's a hex `str`."""