Fix refcounting in relay

syndicate/relay.py

@@ -13,48 +13,57 @@ from .idgen import IdGenerator
 from .schema import externalProtocol as protocol, sturdy, transportAddress
 
 class InboundAssertion:
-    def __init__(self, remote_handle, local_handle, wire_symbols):
+    def __init__(self, remote_handle, local_handle, pins):
         self.remote_handle = remote_handle
         self.local_handle = local_handle
-        self.wire_symbols = wire_symbols
+        self.pins = pins
 
 _next_local_oid = IdGenerator()
 
 class WireSymbol:
-    def __init__(self, oid, ref):
+    def __init__(self, oid, ref, membrane):
         self.oid = oid
         self.ref = ref
+        self.membrane = membrane
         self.count = 0
 
     def __repr__(self):
         return '<ws:%d/%d:%r>' % (self.oid, self.count, self.ref)
 
+    def grab(self, pins):
+        self.count = self.count + 1
+        pins.append(self)
+
+    def drop(self):
+        self.count = self.count - 1
+        if self.count == 0:
+            del self.membrane.oid_map[self.oid]
+            del self.membrane.ref_map[self.ref]
+
 class Membrane:
     def __init__(self):
         self.oid_map = {}
         self.ref_map = {}
 
-    def _get(self, map, key, is_transient, ws_maker):
+    def _get(self, pins, map, key, is_transient, ws_maker):
         ws = map.get(key, None)
-        if ws is None:
+        if ws is None and ws_maker is not None:
             ws = ws_maker()
             self.oid_map[ws.oid] = ws
             self.ref_map[ws.ref] = ws
-        if not is_transient:
+        if not is_transient and ws is not None:
-            ws.count = ws.count + 1
+            ws.grab(pins)
         return ws
 
-    def get_ref(self, local_ref, is_transient, ws_maker):
+    def get_ref(self, pins, local_ref, is_transient, ws_maker):
-        return self._get(self.ref_map, local_ref, is_transient, ws_maker)
+        return self._get(pins, self.ref_map, local_ref, is_transient, ws_maker)
 
-    def get_oid(self, remote_oid, ws_maker):
+    def get_oid(self, pins, remote_oid, ws_maker):
-        return self._get(self.oid_map, remote_oid, False, ws_maker)
+        return self._get(pins, self.oid_map, remote_oid, False, ws_maker)
 
-    def drop(self, ws):
+def drop_all(wss):
-        ws.count = ws.count - 1
+    for ws in wss:
-        if ws.count == 0:
+        ws.drop()
-            del self.oid_map[ws.oid]
-            del self.ref_map[ws.ref]
 
 # There are other kinds of relay. This one has exactly two participants connected to each other.
 class TunnelRelay:
@@ -79,7 +88,7 @@ class TunnelRelay:
 
     def _reset(self):
         self.inbound_assertions = {} # map remote handle to InboundAssertion
-        self.outbound_assertions = {} # map local handle to wire_symbols
+        self.outbound_assertions = {} # map local handle to `WireSymbol`s
         self.exported_references = Membrane()
         self.imported_references = Membrane()
         self.pending_turn = []
@@ -94,49 +103,53 @@ class TunnelRelay:
         self._disconnect()
 
     def deregister(self, handle):
-        for ws in self.outbound_assertions.pop(handle, ()):
+        drop_all(self.outbound_assertions.pop(handle, ()))
-            self.exported_references.drop(ws)
 
-    def _lookup(self, local_oid):
+    def _lookup_exported_oid(self, local_oid, pins):
-        ws = self.exported_references.oid_map.get(local_oid, None)
+        ws = self.exported_references.get_oid(pins, local_oid, None)
-        return _inert_ref if ws is None else ws.ref
+        if ws is None:
+            return _inert_ref
+        return ws.ref
 
-    def register(self, assertion, maybe_handle):
+    def register_imported_oid(self, remote_oid, pins):
-        exported = []
+        self.imported_references.get_oid(pins, remote_oid, None)
+
+    def register(self, target_oid, assertion, maybe_handle):
+        pins = []
+        self.register_imported_oid(target_oid, pins)
         rewritten = map_embeddeds(
-            lambda r: Embedded(self.rewrite_ref_out(r, maybe_handle is None, exported)),
+            lambda r: Embedded(self.rewrite_ref_out(r, maybe_handle is None, pins)),
             assertion)
         if maybe_handle is not None:
-            self.outbound_assertions[maybe_handle] = exported
+            self.outbound_assertions[maybe_handle] = pins
         return rewritten
 
-    def rewrite_ref_out(self, r, is_transient, exported):
+    def rewrite_ref_out(self, r, is_transient, pins):
         if isinstance(r.entity, RelayEntity) and r.entity.relay == self:
             # TODO attenuation
             return sturdy.WireRef.yours(sturdy.Oid(r.entity.oid), ())
         else:
             ws = self.exported_references.get_ref(
-                r, is_transient, lambda: WireSymbol(next(_next_local_oid), r))
+                pins, r, is_transient, lambda: WireSymbol(next(_next_local_oid), r,
-            exported.append(ws)
+                                                          self.exported_references))
             return sturdy.WireRef.mine(sturdy.Oid(ws.oid))
 
-    def rewrite_in(self, turn, assertion):
+    def rewrite_in(self, turn, assertion, pins):
-        imported = []
         rewritten = map_embeddeds(
-            lambda wire_ref: Embedded(self.rewrite_ref_in(turn, wire_ref, imported)),
+            lambda wire_ref: Embedded(self.rewrite_ref_in(turn, wire_ref, pins)),
             assertion)
-        return (rewritten, imported)
+        return rewritten
 
-    def rewrite_ref_in(self, turn, wire_ref, imported):
+    def rewrite_ref_in(self, turn, wire_ref, pins):
         if wire_ref.VARIANT.name == 'mine':
             oid = wire_ref.oid.value
             ws = self.imported_references.get_oid(
-                oid, lambda: WireSymbol(oid, turn.ref(RelayEntity(self, oid))))
+                pins, oid, lambda: WireSymbol(oid, turn.ref(RelayEntity(self, oid)),
-            imported.append(ws)
+                                              self.imported_references))
             return ws.ref
         else:
             oid = wire_ref.oid.value
-            local_ref = self._lookup(oid)
+            local_ref = self._lookup_exported_oid(oid, pins)
             attenuation = wire_ref.attenuation
             if len(attenuation) > 0:
                 raise NotImplementedError('Non-empty attenuations not yet implemented') # TODO
@@ -178,44 +191,45 @@ class TunnelRelay:
 
     def _handle_turn_events(self, turn, events):
         for e in events:
-            ref = self._lookup(e.oid.value)
+            pins = []
+            ref = self._lookup_exported_oid(e.oid.value, pins)
             event = e.event
             variant = event.VARIANT.name
             if variant == 'Assert':
-                self._handle_publish(turn, ref, event.value.assertion.value, event.value.handle.value)
+                self._handle_publish(pins, turn, ref, event.value.assertion.value, event.value.handle.value)
             elif variant == 'Retract':
-                self._handle_retract(turn, ref, event.value.handle.value)
+                self._handle_retract(pins, turn, ref, event.value.handle.value)
             elif variant == 'Message':
-                self._handle_message(turn, ref, event.value.body.value)
+                self._handle_message(pins, turn, ref, event.value.body.value)
             elif variant == 'Sync':
-                self._handle_sync(turn, ref, event.value.peer)
+                self._handle_sync(pins, turn, ref, event.value.peer)
 
-    def _handle_publish(self, turn, ref, assertion, remote_handle):
+    def _handle_publish(self, pins, turn, ref, assertion, remote_handle):
-        (assertion, imported) = self.rewrite_in(turn, assertion)
+        assertion = self.rewrite_in(turn, assertion, pins)
         self.inbound_assertions[remote_handle] = \
-            InboundAssertion(remote_handle, turn.publish(ref, assertion), imported)
+            InboundAssertion(remote_handle, turn.publish(ref, assertion), pins)
 
-    def _handle_retract(self, turn, ref, remote_handle):
+    def _handle_retract(self, pins, turn, ref, remote_handle):
         ia = self.inbound_assertions.pop(remote_handle, None)
         if ia is None:
             raise ValueError('Peer retracted invalid handle %s' % (remote_handle,))
-        for ws in ia.wire_symbols:
+        drop_all(ia.pins)
-            self.imported_references.drop(ws)
+        drop_all(pins)
         turn.retract(ia.local_handle)
 
-    def _handle_message(self, turn, ref, message):
+    def _handle_message(self, pins, turn, ref, message):
-        (message, imported) = self.rewrite_in(turn, message)
+        message = self.rewrite_in(turn, message, pins)
-        if len(imported) > 0:
+        for ws in pins:
-            raise ValueError('Cannot receive transient reference')
+            if ws.count == 1:
+                raise ValueError('Cannot receive transient reference')
         turn.send(ref, message)
+        drop_all(pins)
 
-    def _handle_sync(self, turn, ref, wire_peer):
+    def _handle_sync(self, pins, turn, ref, wire_peer):
-        imported = []
+        peer = self.rewrite_ref_in(turn, wire_peer, pins)
-        peer = self.rewrite_ref_in(turn, wire_peer, imported)
         def done(turn):
             turn.send(peer, True)
-            for ws in imported:
+            drop_all(pins)
-                self.imported_references.drop(ws)
         turn.sync(ref, done)
 
     def _send(self, remote_oid, turn_event):
@@ -269,7 +283,7 @@ class RelayEntity(actor.Entity):
 
     def on_publish(self, turn, assertion, handle):
         self._send(protocol.Event.Assert(protocol.Assert(
-            protocol.Assertion(self.relay.register(assertion, handle)),
+            protocol.Assertion(self.relay.register(self.oid, assertion, handle)),
             protocol.Handle(handle))))
 
     def on_retract(self, turn, handle):
@@ -278,22 +292,23 @@ class RelayEntity(actor.Entity):
 
     def on_message(self, turn, message):
         self._send(protocol.Event.Message(protocol.Message(
-            protocol.Assertion(self.relay.register(message, None)))))
+            protocol.Assertion(self.relay.register(self.oid, message, None)))))
 
     def on_sync(self, turn, peer):
-        exported = []
+        pins = []
-        entity = SyncPeerEntity(self.relay, peer, exported)
+        self.relay.register_imported_oid(self.oid, pins)
-        rewritten = Embedded(self.relay.rewrite_ref_out(turn.ref(entity), False, exported))
+        entity = SyncPeerEntity(self.relay, peer, pins)
+        rewritten = Embedded(self.relay.rewrite_ref_out(turn.ref(entity), False, pins))
         self._send(protocol.Event.Sync(protocol.Sync(rewritten)))
 
 class SyncPeerEntity(actor.Entity):
-    def __init__(self, relay, peer, exported):
+    def __init__(self, relay, peer, pins):
         self.relay = relay
         self.peer = peer
-        self.exported = exported
+        self.pins = pins
 
     def on_message(self, turn, body):
-        self.relay.exported_references.drop(self.exported[0])
+        drop_all(self.pins)
         turn.send(self.peer, body)
 
 async def _default_on_connected(relay):