start moveing stuff to package. Check previous commit for changes to forwardport

Signed-off-by: Marc 'risson' Schmitt <marc.schmitt@risson.space>

packages/django-dramatiq-postgres/django_dramatiq_postgres/models.py

@@ -0,0 +1,67 @@
+from enum import StrEnum, auto
+from uuid import uuid4
+
+import pgtrigger
+from django.db import models
+from django.utils import timezone
+from django.utils.translation import gettext_lazy as _
+
+from django_dramatiq_postgres.conf import Conf
+
+CHANNEL_PREFIX = f"{Conf.channel_prefix}.tasks"
+
+
+class ChannelIdentifier(StrEnum):
+    ENQUEUE = auto()
+    LOCK = auto()
+
+
+class TaskState(models.TextChoices):
+    """Task system-state. Reported by the task runners"""
+
+    QUEUED = "queued"
+    CONSUMED = "consumed"
+    REJECTED = "rejected"
+    DONE = "done"
+
+
+class Task(models.Model):
+    message_id = models.UUIDField(primary_key=True, default=uuid4)
+    queue_name = models.TextField(default="default", help_text=_("Queue name"))
+
+    actor_name = models.TextField(help_text=_("Dramatiq actor name"))
+    message = models.BinaryField(null=True, help_text=_("Message body"))
+    state = models.CharField(
+        default=TaskState.QUEUED,
+        choices=TaskState.choices,
+        help_text=_("Task status"),
+    )
+    mtime = models.DateTimeField(default=timezone.now, help_text=_("Task last modified time"))
+
+    result = models.BinaryField(null=True, help_text=_("Task result"))
+    result_expiry = models.DateTimeField(null=True, help_text=_("Result expiry time"))
+
+    class Meta:
+        abstract = True
+        verbose_name = _("Task")
+        verbose_name_plural = _("Tasks")
+        indexes = (models.Index(fields=("state", "mtime")),)
+        triggers = (
+            pgtrigger.Trigger(
+                name="notify_enqueueing",
+                operation=pgtrigger.Insert | pgtrigger.Update,
+                when=pgtrigger.After,
+                condition=pgtrigger.Q(new__state=TaskState.QUEUED),
+                timing=pgtrigger.Deferred,
+                func=f"""
+                    PERFORM pg_notify(
+                        '{CHANNEL_PREFIX}.' || NEW.queue_name || '.{ChannelIdentifier.ENQUEUE.value}',
+                        NEW.message_id::text
+                    );
+                    RETURN NEW;
+                """,  # noqa: E501
+            ),
+        )
+
+    def __str__(self):
+        return str(self.message_id)