Rework stator to avoid deadlocks on slow databases

Refs #424

activities/migrations/0001_initial.py

@@ -263,6 +263,7 @@ class Migration(migrations.Migration):
                             ("undo_interaction", "Undo Interaction"),
                             ("identity_edited", "Identity Edited"),
                             ("identity_deleted", "Identity Deleted"),
+                            ("identity_created", "Identity Created"),
                         ],
                         max_length=100,
                     ),
@@ -325,6 +326,7 @@ class Migration(migrations.Migration):
                             ("followed", "Followed"),
                             ("boosted", "Boosted"),
                             ("announcement", "Announcement"),
+                            ("identity_created", "Identity Created"),
                         ],
                         max_length=100,
                     ),

activities/migrations/0010_stator_indexes.py

@@ -0,0 +1,55 @@
+# Generated by Django 4.1.4 on 2023-02-04 01:05
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("activities", "0009_alter_timelineevent_index_together"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="emoji",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="fanout",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="hashtag",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="post",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="postattachment",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="postinteraction",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterIndexTogether(
+            name="fanout",
+            index_together={("state_ready", "state_locked_until", "state")},
+        ),
+        migrations.AlterIndexTogether(
+            name="hashtag",
+            index_together={("state_ready", "state_locked_until", "state")},
+        ),
+        migrations.AlterIndexTogether(
+            name="postattachment",
+            index_together={("state_ready", "state_locked_until", "state")},
+        ),
+    ]

stator/models.py

@@ -84,7 +84,7 @@ class StatorModel(models.Model):
     state: StateField
 
     # If this row is up for transition attempts (which it always is on creation!)
-    state_ready = models.BooleanField(default=True)
+    state_ready = models.BooleanField(default=True, db_index=True)
 
     # When the state last actually changed, or the date of instance creation
     state_changed = models.DateTimeField(auto_now_add=True)
@@ -102,6 +102,7 @@ class StatorModel(models.Model):
 
     class Meta:
         abstract = True
+        index_together = ["state_ready", "state_locked_until", "state"]
         # Need this empty indexes to ensure child Models have a Meta.indexes
         # that will look to add indexes (that we inject with class_prepared)
         indexes: list = []

stator/runner.py

@@ -6,7 +6,7 @@ import time
 import traceback
 import uuid
 
-from asgiref.sync import async_to_sync, sync_to_async
+from asgiref.sync import ThreadSensitiveContext, async_to_sync, sync_to_async
 from django.conf import settings
 from django.utils import timezone
 
@@ -15,6 +15,28 @@ from core.models import Config
 from stator.models import StatorModel, Stats
 
 
+class LoopingTask:
+    """
+    Wrapper for having a coroutine go in the background and only have one
+    copy running at a time.
+    """
+
+    def __init__(self, callable):
+        self.callable = callable
+        self.task: asyncio.Task | None = None
+
+    def run(self) -> bool:
+        # If we have a task object, see if we can clear it up
+        if self.task is not None:
+            if self.task.done():
+                self.task = None
+            else:
+                return False
+        # OK, launch a new task
+        self.task = asyncio.create_task(self.callable())
+        return True
+
+
 class StatorRunner:
     """
     Runs tasks on models that are looking for state changes.
@@ -26,7 +48,7 @@ class StatorRunner:
         models: list[type[StatorModel]],
         concurrency: int = getattr(settings, "STATOR_CONCURRENCY", 50),
         concurrency_per_model: int = getattr(
-            settings, "STATOR_CONCURRENCY_PER_MODEL", 20
+            settings, "STATOR_CONCURRENCY_PER_MODEL", 15
         ),
         liveness_file: str | None = None,
         schedule_interval: int = 30,
@@ -53,6 +75,9 @@ class StatorRunner:
         self.last_clean = time.monotonic() - self.schedule_interval
         self.tasks = []
         self.loop_delay = self.minimum_loop_delay
+        self.schedule_task = LoopingTask(self.run_scheduling)
+        self.fetch_task = LoopingTask(self.fetch_and_process_tasks)
+        self.config_task = LoopingTask(self.load_config)
         # For the first time period, launch tasks
         print("Running main task loop")
         try:
@@ -64,22 +89,25 @@ class StatorRunner:
                         # previous one is cancelled)
                         signal.alarm(self.schedule_interval * 2)
                         # Refresh the config
-                        Config.system = await Config.aload_system()
+                        self.config_task.run()
-                        print("Tasks processed this loop:")
+                        if self.schedule_task.run():
-                        for label, number in self.handled.items():
-                            print(f"  {label}: {number}")
                             print("Running cleaning and scheduling")
-                        await self.run_scheduling()
+                        else:
+                            print("Previous scheduling still running...!")
                         # Write liveness file if configured
                         if self.liveness_file:
                             with open(self.liveness_file, "w") as fh:
                                 fh.write(str(int(time.time())))
+                        self.last_clean = time.monotonic()
 
                     # Clear the cleaning breadcrumbs/extra for the main part of the loop
                     sentry.scope_clear(scope)
 
                     self.remove_completed_tasks()
-                    await self.fetch_and_process_tasks()
+
+                    # Fetching is kind of blocking, so we need to do this
+                    # as a separate coroutine
+                    self.fetch_task.run()
 
                     # Are we in limited run mode?
                     if (
@@ -122,17 +150,28 @@ class StatorRunner:
         print("Watchdog timeout exceeded")
         os._exit(2)
 
+    async def load_config(self):
+        """
+        Refreshes config from the DB
+        """
+        Config.system = await Config.aload_system()
+
     async def run_scheduling(self):
         """
         Do any transition cleanup tasks
         """
+        if self.handled:
+            print("Tasks processed since last flush:")
+            for label, number in self.handled.items():
+                print(f"  {label}: {number}")
+        else:
+            print("No tasks handled since last flush.")
         with sentry.start_transaction(op="task", name="stator.run_scheduling"):
             for model in self.models:
-                asyncio.create_task(self.submit_stats(model))
+                await self.submit_stats(model)
-                asyncio.create_task(model.atransition_clean_locks())
+                await model.atransition_clean_locks()
-                asyncio.create_task(model.atransition_schedule_due())
+                await model.atransition_schedule_due()
-                asyncio.create_task(model.atransition_delete_due())
+                await model.atransition_delete_due()
-            self.last_clean = time.monotonic()
 
     async def submit_stats(self, model):
         """
@@ -171,6 +210,7 @@ class StatorRunner:
         Wrapper for atransition_attempt with fallback error handling
         """
         task_name = f"stator.run_transition:{instance._meta.label_lower}#{{id}} from {instance.state}"
+        async with ThreadSensitiveContext():
             with sentry.start_transaction(op="task", name=task_name):
                 sentry.set_context(
                     "instance",

takahe/settings.py

@@ -143,8 +143,8 @@ class Settings(BaseSettings):
     CACHES_DEFAULT: CacheBackendUrl | None = None
 
     # Stator tuning
-    STATOR_CONCURRENCY: int = 100
+    STATOR_CONCURRENCY: int = 50
-    STATOR_CONCURRENCY_PER_MODEL: int = 40
+    STATOR_CONCURRENCY_PER_MODEL: int = 15
 
     PGHOST: str | None = None
     PGPORT: int | None = 5432

users/migrations/0013_stator_indexes.py

@@ -0,0 +1,64 @@
+# Generated by Django 4.1.4 on 2023-02-04 01:05
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("users", "0012_block_states"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="block",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="domain",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="follow",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="identity",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="inboxmessage",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="passwordreset",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterField(
+            model_name="report",
+            name="state_ready",
+            field=models.BooleanField(db_index=True, default=True),
+        ),
+        migrations.AlterIndexTogether(
+            name="domain",
+            index_together={("state_ready", "state_locked_until", "state")},
+        ),
+        migrations.AlterIndexTogether(
+            name="inboxmessage",
+            index_together={("state_ready", "state_locked_until", "state")},
+        ),
+        migrations.AlterIndexTogether(
+            name="passwordreset",
+            index_together={("state_ready", "state_locked_until", "state")},
+        ),
+        migrations.AlterIndexTogether(
+            name="report",
+            index_together={("state_ready", "state_locked_until", "state")},
+        ),
+    ]