sharding (reminders): Adapt for sharding.

Restrict reminder execution to shard `0`.
Add a poll on shard `0` to pick up new reminders.
Check whether the reminder still exists on execution.

bot/modules/reminders/commands.py

@@ -3,6 +3,7 @@ import asyncio
 import datetime
 import discord
 
+from meta import sharding
 from utils.lib import parse_dur, parse_ranges, multiselect_regex
 
 from .module import module
@@ -55,7 +56,7 @@ async def cmd_remindme(ctx, flags):
         if not rows:
             return await ctx.reply("You have no reminders to remove!")
 
-        live = Reminder.fetch(*(row.reminderid for row in rows))
+        live = [Reminder(row.reminderid) for row in rows]
 
         if not ctx.args:
             lines = []
@@ -209,6 +210,7 @@ async def cmd_remindme(ctx, flags):
         )
 
         # Schedule reminder
+        if sharding.shard_number == 0:
             reminder.schedule()
 
         # Ack
@@ -231,7 +233,7 @@ async def cmd_remindme(ctx, flags):
         if not rows:
             return await ctx.reply("You have no reminders!")
 
-        live = Reminder.fetch(*(row.reminderid for row in rows))
+        live = [Reminder(row.reminderid) for row in rows]
 
         lines = []
         num_field = len(str(len(live) - 1))

bot/modules/reminders/reminder.py

@@ -1,8 +1,9 @@
 import asyncio
 import datetime
+import logging
 import discord
 
-from meta import client
+from meta import client, sharding
 from utils.lib import strfdur
 
 from .data import reminders
@@ -46,7 +47,10 @@ class Reminder:
                 cls._live_reminders[reminderid].cancel()
 
         # Remove from data
-        reminders.delete_where(reminderid=reminderids)
+        if reminderids:
+            return reminders.delete_where(reminderid=reminderids)
+        else:
+            return []
 
     @property
     def data(self):
@@ -134,10 +138,16 @@ class Reminder:
         """
         Execute the reminder.
         """
+        if not self.data:
+            # Reminder deleted elsewhere
+            return
+
         if self.data.userid in client.user_blacklist():
             self.delete(self.reminderid)
             return
 
+        userid = self.data.userid
+
         # Build the message embed
         embed = discord.Embed(
             title="You asked me to remind you!",
@@ -155,8 +165,26 @@ class Reminder:
                 )
             )
 
+        # Update the reminder data, and reschedule if required
+        if self.data.interval:
+            next_time = self.data.remind_at + datetime.timedelta(seconds=self.data.interval)
+            rows = reminders.update_where(
+                {'remind_at': next_time},
+                reminderid=self.reminderid
+            )
+            self.schedule()
+        else:
+            rows = self.delete(self.reminderid)
+        if not rows:
+            # Reminder deleted elsewhere
+            return
+
         # Send the message, if possible
-        user = self.user
+        if not (user := client.get_user(userid)):
+            try:
+                user = await client.fetch_user(userid)
+            except discord.HTTPException:
+                pass
         if user:
             try:
                 await user.send(embed=embed)
@@ -164,17 +192,32 @@ class Reminder:
                 # Nothing we can really do here. Maybe tell the user about their reminder next time?
                 pass
 
-        # Update the reminder data, and reschedule if required
-        if self.data.interval:
-            next_time = self.data.remind_at + datetime.timedelta(seconds=self.data.interval)
-            reminders.update_where({'remind_at': next_time}, reminderid=self.reminderid)
-            self.schedule()
-        else:
-            self.delete(self.reminderid)
+
+async def reminder_poll(client):
+    """
+    One client/shard must continually poll for new or deleted reminders.
+    """
+    # TODO: Clean this up with database signals or IPC
+    while True:
+        await asyncio.sleep(60)
+
+        client.log(
+            "Running new reminder poll.",
+            context="REMINDERS",
+            level=logging.DEBUG
+        )
+
+        rids = {row.reminderid for row in reminders.fetch_rows_where()}
+
+        to_delete = (rid for rid in Reminder._live_reminders if rid not in rids)
+        Reminder.delete(*to_delete)
+
+        [Reminder(rid).schedule() for rid in rids if rid not in Reminder._live_reminders]
 
 
 @module.launch_task
 async def schedule_reminders(client):
+    if sharding.shard_number == 0:
         rows = reminders.fetch_rows_where()
         for row in rows:
             Reminder(row.reminderid).schedule()
@@ -182,3 +225,5 @@ async def schedule_reminders(client):
             "Scheduled {} reminders.".format(len(rows)),
             context="LAUNCH_REMINDERS"
         )
+        if sharding.sharded:
+            asyncio.create_task(reminder_poll(client))