Use DB for clean tracking

Author: Archmonger

CHANGELOG.md

@@ -34,7 +34,9 @@ Using the following categories, list your changes in this order:
 
 ## [Unreleased]
 
--   Nothing yet!
+### Changed
+
+-   A thread-safe cache is no longer required.
 
 ## [3.2.1] - 2023-06-29
 

docs/python/settings.py

@@ -1,4 +1,4 @@
-# ReactPy requires a multiprocessing-safe and thread-safe cache.
+# ReactPy benefits from a fast, well indexed cache.
 REACTPY_CACHE = "default"
 
 # ReactPy requires a multiprocessing-safe and thread-safe database.

src/reactpy_django/components.py

@@ -210,7 +210,6 @@ def _cached_static_contents(static_path: str):
         )
 
     # Fetch the file from cache, if available
-    # Cache is preferrable to `use_memo` due to multiprocessing capabilities
     last_modified_time = os.stat(abs_path).st_mtime
     cache_key = f"reactpy_django:static_contents:{static_path}"
     file_contents = caches[REACTPY_CACHE].get(

src/reactpy_django/migrations/0004_config.py

@@ -0,0 +1,27 @@
+# Generated by Django 4.2.3 on 2023-08-04 05:49
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("reactpy_django", "0003_componentsession_delete_componentparams"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="Config",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("cleaned_at", models.DateTimeField(auto_now_add=True)),
+            ],
+        ),
+    ]

src/reactpy_django/models.py

@@ -9,3 +9,19 @@ class ComponentSession(models.Model):
     uuid = models.UUIDField(primary_key=True, editable=False, unique=True)  # type: ignore
     params = models.BinaryField(editable=False)  # type: ignore
     last_accessed = models.DateTimeField(auto_now_add=True)  # type: ignore
+
+
+class Config(models.Model):
+    """A singleton model for storing ReactPy configuration."""
+
+    cleaned_at = models.DateTimeField(auto_now_add=True)  # type: ignore
+
+    def save(self, *args, **kwargs):
+        """Singleton save method."""
+        self.pk = 1
+        super().save(*args, **kwargs)
+
+    @classmethod
+    def load(cls):
+        obj, created = cls.objects.get_or_create(pk=1)
+        return obj

src/reactpy_django/utils.py

@@ -12,7 +12,6 @@
 from typing import Any, Callable, Sequence
 
 from channels.db import database_sync_to_async
-from django.core.cache import caches
 from django.db.models import ManyToManyField, ManyToOneRel, prefetch_related_objects
 from django.db.models.base import Model
 from django.db.models.query import QuerySet
@@ -24,7 +23,6 @@
 
 from reactpy_django.exceptions import ComponentDoesNotExistError, ComponentParamError
 
-
 _logger = logging.getLogger(__name__)
 _component_tag = r"(?P<tag>component)"
 _component_path = r"(?P<path>\"[^\"'\s]+\"|'[^\"'\s]+')"
@@ -332,39 +330,22 @@ def create_cache_key(*args):
 def db_cleanup(immediate: bool = False):
     """Deletes expired component sessions from the database.
     This function may be expanded in the future to include additional cleanup tasks."""
-    from .config import (
-        REACTPY_CACHE,
-        REACTPY_DATABASE,
-        REACTPY_DEBUG_MODE,
-        REACTPY_RECONNECT_MAX,
-    )
-    from .models import ComponentSession
+    from .config import REACTPY_DATABASE, REACTPY_DEBUG_MODE, REACTPY_RECONNECT_MAX
+    from .models import ComponentSession, Config
 
     clean_started_at = datetime.now()
-    cache_key: str = create_cache_key("last_cleaned")
-    now_str: str = datetime.strftime(timezone.now(), DATE_FORMAT)
-    cleaned_at_str: str = caches[REACTPY_CACHE].get(cache_key)
-    cleaned_at: datetime = timezone.make_aware(
-        datetime.strptime(cleaned_at_str or now_str, DATE_FORMAT)
-    )
+    config = Config.load()
+    cleaned_at = config.cleaned_at
     clean_needed_by = cleaned_at + timedelta(seconds=REACTPY_RECONNECT_MAX)
-    expires_by: datetime = timezone.now() - timedelta(seconds=REACTPY_RECONNECT_MAX)
-
-    # Component params exist in the DB, but we don't know when they were last cleaned
-    if not cleaned_at_str and ComponentSession.objects.using(REACTPY_DATABASE).all():
-        _logger.warning(
-            "ReactPy has detected component sessions in the database, "
-            "but no timestamp was found in cache. This may indicate that "
-            "the cache has been cleared."
-        )
+    expires_by = timezone.now() - timedelta(seconds=REACTPY_RECONNECT_MAX)
 
     # Delete expired component parameters
-    # Use timestamps in cache (`cleaned_at_str`) as a no-dependency rate limiter
-    if immediate or not cleaned_at_str or timezone.now() >= clean_needed_by:
+    if immediate or timezone.now() >= clean_needed_by:
         ComponentSession.objects.using(REACTPY_DATABASE).filter(
             last_accessed__lte=expires_by
         ).delete()
-        caches[REACTPY_CACHE].set(cache_key, now_str, timeout=None)
+        config.cleaned_at = timezone.now()
+        config.save()
 
     # Check if cleaning took abnormally long
     clean_duration = datetime.now() - clean_started_at

tests/test_app/admin.py

@@ -1,4 +1,6 @@
 from django.contrib import admin
+from reactpy_django.models import ComponentSession, Config
+
 from test_app.models import (
     AsyncForiegnChild,
     AsyncRelationalChild,
@@ -10,8 +12,6 @@
     TodoItem,
 )
 
-from reactpy_django.models import ComponentSession
-
 
 @admin.register(TodoItem)
 class TodoItemAdmin(admin.ModelAdmin):
@@ -55,4 +55,9 @@ class AsyncForiegnChildAdmin(admin.ModelAdmin):
 
 @admin.register(ComponentSession)
 class ComponentSessionAdmin(admin.ModelAdmin):
-    list_display = ("uuid", "last_accessed")
+    list_display = ["uuid", "last_accessed"]
+
+
+@admin.register(Config)
+class ConfigAdmin(admin.ModelAdmin):
+    list_display = ["pk", "cleaned_at"]