Add example for events.

Author: rlubke

.coveragerc

@@ -1,6 +1,6 @@
 [run]
 omit =
-  coherence/messages_pb2.py
-  coherence/messages_pb2_grpc.py
-  coherence/services_pb2.py
-  coherence/services_pb2_grpc.py
+  src/coherence/messages_pb2.py
+  src/coherence/messages_pb2_grpc.py
+  src/coherence/services_pb2.py
+  src/coherence/services_pb2_grpc.py

examples/events.py

@@ -0,0 +1,87 @@
+# Copyright (c) 2023, Oracle and/or its affiliates.
+# Licensed under the Universal Permissive License v 1.0 as shown at
+# https://oss.oracle.com/licenses/upl.
+
+import asyncio
+
+from coherence import Filters, NamedMap, Session
+from coherence.event import MapLifecycleEvent, MapListener
+from coherence.filter import MapEventFilter
+
+
+async def do_run() -> None:
+    """
+    Demonstrates listeners for entry events and cache lifecycle.
+
+    :return: None
+    """
+    session: Session = Session()
+    try:
+        namedMap: NamedMap[int, str] = await session.get_map("listeners-map")
+        await namedMap.put(1, "1")
+
+        print("NamedMap lifecycle events")
+
+        namedMap.on(MapLifecycleEvent.RELEASED, lambda x: print("RELEASED", x))
+        namedMap.on(MapLifecycleEvent.TRUNCATED, lambda x: print("TRUNCATE", x))
+        namedMap.on(MapLifecycleEvent.DESTROYED, lambda x: print("DESTROYED", x))
+
+        print("Truncating the NamedMap; this should generate an event ...")
+        await namedMap.truncate()
+        await asyncio.sleep(1)
+
+        print("Releasing the NamedMap; this should generate an event ...")
+        namedMap.release()
+        await asyncio.sleep(1)
+
+        print("Destroying the NamedMap; this should generate an event ...")
+        await namedMap.destroy()
+        await asyncio.sleep(1)
+
+        print("\n\nNamedMap eventy events")
+
+        namedMap = await session.get_map("listeners-map")
+
+        listener1: MapListener[int, str] = MapListener()
+        listener1.on_any(lambda e: print(e))
+
+        print("Added listener for all events")
+        print("Events will be generated when an entry is inserted, updated, and removed")
+        await namedMap.add_map_listener(listener1)
+
+        await namedMap.put(1, "1")
+        await namedMap.put(1, "2")
+        await namedMap.remove(1)
+        await asyncio.sleep(1)
+
+        await namedMap.remove_map_listener(listener1)
+
+        print("\nAdded listener for all entries, but only when they are inserted")
+        filter = Filters.event(Filters.always(), MapEventFilter.INSERTED)
+        await namedMap.add_map_listener(listener1, filter)
+
+        await namedMap.put(1, "1")
+        await namedMap.put(1, "2")
+        await namedMap.remove(1)
+        await asyncio.sleep(1)
+
+        await namedMap.remove_map_listener(listener1, filter)
+
+        print("\nAdded listener for entries with a length larger than one, but only when they are updated or removed")
+        filter = Filters.event(Filters.greater("length()", 1), MapEventFilter.UPDATED | MapEventFilter.DELETED)
+        await namedMap.add_map_listener(listener1, filter)
+
+        for i in range(12):
+            await namedMap.put(i, str(i))
+            await namedMap.put(i, str(i + 1))
+            await namedMap.remove(i)
+
+        await asyncio.sleep(1)
+
+        await namedMap.remove_map_listener(listener1, filter)
+        await namedMap.clear()
+    finally:
+        await session.close()
+
+
+asyncio.run(do_run())

src/coherence/client.py

@@ -562,9 +562,9 @@ async def clear(self) -> None:
         r = self._request_factory.clear_request()
         await self._client_stub.clear(r)
 
-    @_pre_call_cache
     async def destroy(self) -> None:
         self._internal_emitter.once(MapLifecycleEvent.DESTROYED.value)
+        self._internal_emitter.emit(MapLifecycleEvent.DESTROYED.value, self.name)
         r = self._request_factory.destroy_request()
         await self._client_stub.destroy(r)
 
@@ -1211,11 +1211,13 @@ def _setup_event_handlers(self, client: NamedCacheClient[K, V]) -> None:
         this: Session = self
 
         def on_destroyed(name: str) -> None:
-            del this._caches[name]
+            if name in this._caches:
+                del this._caches[name]
             self._emitter.emit(MapLifecycleEvent.DESTROYED.value, name)
 
         def on_released(name: str) -> None:
-            del this._caches[name]
+            if name in this._caches:
+                del this._caches[name]
             self._emitter.emit(MapLifecycleEvent.RELEASED.value, name)
 
         client.on(MapLifecycleEvent.DESTROYED, on_destroyed)