xep-0115: perf: avoid simultaneous disco info queries for the same verstring

slixmpp/plugins/xep_0115/caps.py

@@ -7,7 +7,8 @@ import logging
 import hashlib
 import base64
 
-from asyncio import Future
+from asyncio import Future, Lock
+from collections import defaultdict
 from typing import Optional
 
 from slixmpp import __version__
@@ -94,6 +95,9 @@ class XEP_0115(BasePlugin):
         disco.assign_verstring = self.assign_verstring
         disco.get_verstring = self.get_verstring
 
+        # prevent concurrent fetches for the same hash
+        self._locks = defaultdict(Lock)
+
     def plugin_end(self):
         self.xmpp['xep_0030'].del_feature(feature=stanza.Capabilities.namespace)
         self.xmpp.del_filter('out', self._filter_add_caps)
@@ -137,7 +141,7 @@ class XEP_0115(BasePlugin):
 
         self.xmpp.event('entity_caps', p)
 
-    async def _process_caps(self, pres):
+    async def _process_caps(self, pres: Presence):
         if not pres['caps']['hash']:
             log.debug("Received unsupported legacy caps: %s, %s, %s",
                     pres['caps']['node'],
@@ -147,7 +151,11 @@ class XEP_0115(BasePlugin):
             return
 
         ver = pres['caps']['ver']
+        async with self._locks[ver]:
+            await self._process_caps_wrapped(pres, ver)
+        self._locks.pop(ver, None)
 
+    async def _process_caps_wrapped(self, pres: Presence, ver: str):
         existing_verstring = await self.get_verstring(pres['from'].full)
         if str(existing_verstring) == str(ver):
             return

tests/test_stream_xep_0115.py

@@ -0,0 +1,76 @@
+import logging
+import unittest
+from slixmpp.test import SlixTest
+
+
+class TestCaps(SlixTest):
+    def setUp(self):
+        self.stream_start(plugins=["xep_0115"])
+
+    def testConcurrentSameHash(self):
+        """
+        Check that we only resolve a given ver string to a disco info once,
+        even if we receive several presences with that same ver string
+        consecutively.
+        """
+        self.recv(  # language=XML
+            """
+            <presence from='romeo@montague.lit/orchard'>
+              <c xmlns='http://jabber.org/protocol/caps'
+                 hash='sha-1'
+                 node='a-node'
+                 ver='h0TdMvqNR8FHUfFG1HauOLYZDqE='/>
+            </presence>
+            """
+        )
+        self.recv(  # language=XML
+            """
+            <presence from='i-dont-know-much-shakespeare@montague.lit/orchard'>
+              <c xmlns='http://jabber.org/protocol/caps'
+                 hash='sha-1'
+                 node='a-node'
+                 ver='h0TdMvqNR8FHUfFG1HauOLYZDqE='/>
+            </presence>
+            """
+        )
+        self.send(  # language=XML
+            """
+            <iq xmlns="jabber:client"
+                id="1"
+                to="romeo@montague.lit/orchard"
+                type="get">
+              <query xmlns="http://jabber.org/protocol/disco#info"
+                     node="a-node#h0TdMvqNR8FHUfFG1HauOLYZDqE="/>
+            </iq>
+            """
+        )
+        self.send(None)
+        self.recv(  # language=XML
+            """
+            <iq from='romeo@montague.lit/orchard'
+                id='1'
+                type='result'>
+              <query xmlns='http://jabber.org/protocol/disco#info'
+                     node='a-nodes#h0TdMvqNR8FHUfFG1HauOLYZDqE='>
+                <identity category='client' name='a client' type='pc'/>
+                <feature var='http://jabber.org/protocol/caps'/>
+              </query>
+            </iq>
+            """
+        )
+        self.send(None)
+        self.assertTrue(
+            self.xmpp["xep_0030"].supports(
+                "romeo@montague.lit/orchard", "http://jabber.org/protocol/caps"
+            )
+        )
+        self.assertTrue(
+            self.xmpp["xep_0030"].supports(
+                "i-dont-know-much-shakespeare@montague.lit/orchard",
+                "http://jabber.org/protocol/caps",
+            )
+        )
+
+
+logging.basicConfig(level=logging.DEBUG)
+suite = unittest.TestLoader().loadTestsFromTestCase(TestCaps)