Speed Up Sync Cog Loading

The user syncer was blocking the startup of the sync cog due to having
to perform thousands of pointless member fetch requests. This speeds up
that process by increasing the probability that the cache is up-to-date
using `Guild.chunked`, and limiting the fetches to members who were in
the guild during the previous sync only.

Co-authored-by: ChrisJL <[email protected]>
Co-authored-by: wookie184 <[email protected]>
Signed-off-by: Hassan Abouelela <[email protected]>

3 files changed, 18 insertions, 3 deletions

diff --git a/bot/exts/backend/sync/_cog.py b/bot/exts/backend/sync/_cog.py
index a5bf82397..4ec822d3f 100644
--- a/bot/exts/backend/sync/_cog.py
+++ b/bot/exts/backend/sync/_cog.py
@@ -1,3 +1,4 @@
+import asyncio
 from typing import Any, Dict
 
 from botcore.site_api import ResponseCodeError
@@ -27,6 +28,11 @@ class Sync(Cog):
         if guild is None:
             return
 
+        log.info("Waiting for guild to be chunked to start syncers.")
+        while not guild.chunked:
+            await asyncio.sleep(10)
+        log.info("Starting syncers.")
+
         for syncer in (_syncers.RoleSyncer, _syncers.UserSyncer):
             await syncer.sync(guild)
 
diff --git a/bot/exts/backend/sync/_syncers.py b/bot/exts/backend/sync/_syncers.py
index e1c4541ef..799137cb9 100644
--- a/bot/exts/backend/sync/_syncers.py
+++ b/bot/exts/backend/sync/_syncers.py
@@ -2,6 +2,7 @@ import abc
 import typing as t
 from collections import namedtuple
 
+import discord.errors
 from botcore.site_api import ResponseCodeError
 from discord import Guild
 from discord.ext.commands import Context
@@ -9,7 +10,6 @@ from more_itertools import chunked
 
 import bot
 from bot.log import get_logger
-from bot.utils.members import get_or_fetch_member
 
 log = get_logger(__name__)
 
@@ -157,7 +157,16 @@ class UserSyncer(Syncer):
                 if db_user[db_field] != guild_value:
                     updated_fields[db_field] = guild_value
 
-            if guild_user := await get_or_fetch_member(guild, db_user["id"]):
+            guild_user = guild.get_member(db_user["id"])
+            if not guild_user and db_user["in_guild"]:
+                # The member was in the guild during the last sync.
+                # We try to fetch them to verify cache integrity.
+                try:
+                    guild_user = await guild.fetch_member(db_user["id"])
+                except discord.errors.NotFound:
+                    guild_user = None
+
+            if guild_user:
                 seen_guild_users.add(guild_user.id)
 
                 maybe_update("name", guild_user.name)
diff --git a/tests/helpers.py b/tests/helpers.py
index a6e4bdd66..5f3111616 100644
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -171,7 +171,7 @@ class MockGuild(CustomMockMixin, unittest.mock.Mock, HashableMixin):
     spec_set = guild_instance
 
     def __init__(self, roles: Optional[Iterable[MockRole]] = None, **kwargs) -> None:
-        default_kwargs = {'id': next(self.discord_id), 'members': []}
+        default_kwargs = {'id': next(self.discord_id), 'members': [], "chunked": True}
         super().__init__(**collections.ChainMap(kwargs, default_kwargs))
 
         self.roles = [MockRole(name="@everyone", position=1, id=0)]