Port RobotWebTools#464, RobotWebTools#496, and RobotWebTools#502 from…

… ROS1 branch

RobotWebTools#464
RobotWebTools#496
RobotWebTools#502

rosbridge_library/src/rosbridge_library/capabilities/subscribe.py

@@ -84,7 +84,7 @@ def unregister(self):
         """Unsubscribes this subscription and cleans up resources"""
         manager.unsubscribe(self.client_id, self.topic)
         with self.handler_lock:
-            self.handler.finish()
+            self.handler.finish(block=False)
         self.clients.clear()
 
     def subscribe(

rosbridge_library/src/rosbridge_library/internal/subscribers.py

@@ -222,6 +222,7 @@ class SubscriberManager:
     """
 
     def __init__(self):
+        self._lock = Lock()
         self._subscribers = {}
 
     def subscribe(self, client_id, topic, callback, node_handle, msg_type=None, raw=False):
@@ -234,15 +235,16 @@ def subscribe(self, client_id, topic, callback, node_handle, msg_type=None, raw=
         msg_type  -- (optional) the type of the topic
 
         """
-        if topic not in self._subscribers:
-            self._subscribers[topic] = MultiSubscriber(
-                topic, client_id, callback, node_handle, msg_type=msg_type, raw=raw
-            )
-        else:
-            self._subscribers[topic].subscribe(client_id, callback)
+        with self._lock:
+            if topic not in self._subscribers:
+                self._subscribers[topic] = MultiSubscriber(
+                    topic, client_id, callback, node_handle, msg_type=msg_type, raw=raw
+                )
+            else:
+                self._subscribers[topic].subscribe(client_id, callback)
 
-        if msg_type is not None and not raw:
-            self._subscribers[topic].verify_type(msg_type)
+            if msg_type is not None and not raw:
+                self._subscribers[topic].verify_type(msg_type)
 
     def unsubscribe(self, client_id, topic):
         """Unsubscribe from a topic
@@ -252,14 +254,15 @@ def unsubscribe(self, client_id, topic):
         topic     -- the topic to unsubscribe from
 
         """
-        if topic not in self._subscribers:
-            return
+        with self._lock:
+            if topic not in self._subscribers:
+                return
 
-        self._subscribers[topic].unsubscribe(client_id)
+            self._subscribers[topic].unsubscribe(client_id)
 
-        if not self._subscribers[topic].has_subscribers():
-            self._subscribers[topic].unregister()
-            del self._subscribers[topic]
+            if not self._subscribers[topic].has_subscribers():
+                self._subscribers[topic].unregister()
+                del self._subscribers[topic]
 
 
 manager = SubscriberManager()

rosbridge_library/src/rosbridge_library/internal/subscription_modifiers.py

@@ -30,6 +30,9 @@
 # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 # POSSIBILITY OF SUCH DAMAGE.
 
+import sys
+import traceback
+from collections import deque
 from threading import Condition, Thread
 from time import time
 
@@ -77,7 +80,7 @@ def transition(self):
         else:
             return QueueMessageHandler(self)
 
-    def finish(self):
+    def finish(self, block=True):
         pass
 
 
@@ -94,7 +97,7 @@ def transition(self):
         else:
             return QueueMessageHandler(self)
 
-    def finish(self):
+    def finish(self, block=True):
         pass
 
 
@@ -103,17 +106,17 @@ def __init__(self, previous_handler):
         Thread.__init__(self)
         MessageHandler.__init__(self, previous_handler)
         self.daemon = True
-        self.queue = []
+        self.queue = deque(maxlen=self.queue_length)
         self.c = Condition()
         self.alive = True
         self.start()
 
     def handle_message(self, msg):
         with self.c:
+            if not self.alive:
+                return
             should_notify = len(self.queue) == 0
             self.queue.append(msg)
-            if len(self.queue) > self.queue_length:
-                del self.queue[0 : len(self.queue) - self.queue_length]
             if should_notify:
                 self.c.notify()
 
@@ -126,37 +129,40 @@ def transition(self):
             return ThrottleMessageHandler(self)
         else:
             with self.c:
-                if len(self.queue) > self.queue_length:
-                    del self.queue[0 : len(self.queue) - self.queue_length]
+                old_queue = self.queue
+                self.queue = deque(maxlen=self.queue_length)
+                while len(old_queue) > 0:
+                    self.queue.append(old_queue.popleft())
                 self.c.notify()
             return self
 
-    def finish(self):
+    def finish(self, block=True):
         """If throttle was set to 0, this pushes all buffered messages"""
         # Notify the thread to finish
         with self.c:
             self.alive = False
             self.c.notify()
 
-        self.join()
+        if block:
+            self.join()
 
     def run(self):
         while self.alive:
+            msg = None
             with self.c:
-                while self.alive and (self.time_remaining() > 0 or len(self.queue) == 0):
-                    if len(self.queue) == 0:
-                        self.c.wait()
-                    else:
-                        self.c.wait(self.time_remaining())
+                if len(self.queue) == 0:
+                    self.c.wait()
+                else:
+                    self.c.wait(self.time_remaining())
                 if self.alive and self.time_remaining() == 0 and len(self.queue) > 0:
-                    try:
-                        MessageHandler.handle_message(self, self.queue[0])
-                    except Exception:
-                        pass
-                    del self.queue[0]
+                    msg = self.queue.popleft()
+            if msg is not None:
+                try:
+                    MessageHandler.handle_message(self, msg)
+                except:
+                    traceback.print_exc(file=sys.stderr)
         while self.time_remaining() == 0 and len(self.queue) > 0:
             try:
                 MessageHandler.handle_message(self, self.queue[0])
-            except Exception:
-                pass
-            del self.queue[0]
+            except:
+                traceback.print_exc(file=sys.stderr)

rosbridge_library/test/internal/subscribers/test_subscription_modifiers.py

@@ -75,6 +75,42 @@ def cb(msg):
         finally:
             handler.finish()
 
+    def test_queue_message_handler_dropping(self):
+        received = {"msgs": []}
+
+        def cb(msg):
+            received["msgs"].append(msg)
+            time.sleep(1)
+
+        queue_length = 5
+        msgs = range(queue_length * 5)
+
+        handler = subscribe.MessageHandler(None, cb)
+
+        handler = handler.set_queue_length(queue_length)
+        self.assertIsInstance(handler, subscribe.QueueMessageHandler)
+
+        # send all messages at once.
+        # only the first and the last queue_length should get through,
+        # because the callbacks are blocked.
+        for x in msgs:
+            handler.handle_message(x)
+            # yield the thread so the first callback can append,
+            # otherwise the first handled value is non-deterministic.
+            time.sleep(0)
+
+        # wait long enough for all the callbacks, and then some.
+        time.sleep(queue_length + 3)
+
+        try:
+            self.assertEqual([msgs[0]] + msgs[-queue_length:], received["msgs"])
+        except:
+            handler.finish()
+            raise
+
+        handler.finish()
+
+
     def test_queue_message_handler_rate(self):
         handler = subscribe.MessageHandler(None, self.dummy_cb)
         self.help_test_queue_rate(handler, 50, 10)

rosbridge_server/src/rosbridge_server/websocket_handler.py

@@ -34,6 +34,7 @@
 import threading
 import traceback
 import uuid
+from collections import deque
 from functools import partial, wraps
 
 from rosbridge_library.rosbridge_protocol import RosbridgeProtocol
@@ -65,6 +66,50 @@ def wrapper(*args, **kwargs):
     return wrapper
 
 
+class IncomingQueue(threading.Thread):
+    """Decouples incoming messages from the Tornado thread.
+
+    This mitigates cases where outgoing messages are blocked by incoming,
+    and vice versa.
+    """
+    def __init__(self, protocol):
+        threading.Thread.__init__(self)
+        self.daemon = True
+        self.queue = deque()
+        self.protocol = protocol
+
+        self.cond = threading.Condition()
+        self._finished = False
+
+    def finish(self):
+        """Clear the queue and do not accept further messages."""
+        with self.cond:
+            self._finished = True
+            while len(self.queue) > 0:
+                self.queue.popleft()
+            self.cond.notify()
+
+    def push(self, msg):
+        with self.cond:
+            self.queue.append(msg)
+            self.cond.notify()
+
+    def run(self):
+        while True:
+            with self.cond:
+                if len(self.queue) == 0 and not self._finished:
+                    self.cond.wait()
+
+                if self._finished:
+                    break
+
+                msg = self.queue.popleft()
+
+            self.protocol.incoming(msg)
+
+        self.protocol.finish()
+
+
 class RosbridgeWebSocket(WebSocketHandler):
     client_id_seed = 0
     clients_connected = 0
@@ -94,6 +139,8 @@ def open(self):
             self.protocol = RosbridgeProtocol(
                 cls.client_id_seed, cls.node_handle, parameters=parameters
             )
+            self.incoming_queue = IncomingQueue(self.protocol)
+            self.incoming_queue.start()
             self.protocol.outgoing = self.send_message
             self.set_nodelay(True)
             self._write_lock = threading.RLock()
@@ -115,18 +162,18 @@ def open(self):
     def on_message(self, message):
         if isinstance(message, bytes):
             message = message.decode("utf-8")
-        self.protocol.incoming(message)
+        self.incoming_queue.push(message)
 
     @log_exceptions
     def on_close(self):
         cls = self.__class__
         cls.clients_connected -= 1
-        self.protocol.finish()
         if cls.client_manager:
             cls.client_manager.remove_client(self.client_id, self.request.remote_ip)
         cls.node_handle.get_logger().info(
             f"Client disconnected. {cls.clients_connected} clients total."
         )
+        self.incoming_queue.finish()
 
     def send_message(self, message):
         if isinstance(message, bson.BSON):