warn when the server stops listening for connections because its in overflow

2 files changed, 35 insertions, 1 deletions

diff --git a/src/waitress/server.py b/src/waitress/server.py
index b053c69..639b9de 100644
--- a/src/waitress/server.py
+++ b/src/waitress/server.py
@@ -179,6 +179,7 @@ class BaseWSGIServer(wasyncore.dispatcher):
     next_channel_cleanup = 0
     socketmod = socket  # test shim
     asyncore = wasyncore  # test shim
+    in_connection_overflow = False
 
     def __init__(
         self,
@@ -296,7 +297,26 @@ class BaseWSGIServer(wasyncore.dispatcher):
         if now >= self.next_channel_cleanup:
             self.next_channel_cleanup = now + self.adj.cleanup_interval
             self.maintenance(now)
-        return self.accepting and len(self._map) < self.adj.connection_limit
+
+        if (
+            not self.in_connection_overflow
+            and len(self._map) >= self.adj.connection_limit
+        ):
+            self.in_connection_overflow = True
+            self.logger.warning(
+                'server active connections reached the connection limit, '
+                'no longer accepting new connections'
+            )
+        elif (
+            self.in_connection_overflow
+            and len(self._map) < self.adj.connection_limit
+        ):
+            self.in_connection_overflow = False
+            self.logger.info(
+                'server active connections dropped below the connection limit, '
+                'listening again'
+            )
+        return self.accepting and not self.in_connection_overflow
 
     def writable(self):
         return False
diff --git a/tests/test_server.py b/tests/test_server.py
index 05f6b4e..508b382 100644
--- a/tests/test_server.py
+++ b/tests/test_server.py
@@ -185,6 +185,7 @@ class TestWSGIServer(unittest.TestCase):
         inst.adj = DummyAdj
         inst._map = {"a": 1, "b": 2}
         self.assertFalse(inst.readable())
+        self.assertTrue(inst.in_connection_overflow)
 
     def test_readable_maplen_lt_connection_limit(self):
         inst = self._makeOneWithMap()
@@ -192,6 +193,19 @@ class TestWSGIServer(unittest.TestCase):
         inst.adj = DummyAdj
         inst._map = {}
         self.assertTrue(inst.readable())
+        self.assertFalse(inst.in_connection_overflow)
+
+    def test_readable_maplen_toggles_connection_overflow(self):
+        inst = self._makeOneWithMap()
+        inst.accepting = True
+        inst.adj = DummyAdj
+        inst._map = {"a": 1, "b": 2}
+        self.assertFalse(inst.in_connection_overflow)
+        self.assertFalse(inst.readable())
+        self.assertTrue(inst.in_connection_overflow)
+        inst._map = {}
+        self.assertTrue(inst.readable())
+        self.assertFalse(inst.in_connection_overflow)
 
     def test_readable_maintenance_false(self):
         import time