feat: add post notify subscription

pyproject.toml

@@ -11,6 +11,8 @@ django = "^4.2.5"
 strawberry-graphql-django = "^0.17.4"
 django-extensions = "^3.2.3"
 pillow = "^10.0.1"
+strawberry-graphql = {extras = ["channels"], version = "^0.209.6"}
+daphne = "^4.0.0"
 
 
 [tool.poetry.group.dev.dependencies]

server/app/blog/graph/mutations.py

@@ -3,6 +3,9 @@
 
 import strawberry
 import strawberry_django
+from asgiref.sync import async_to_sync
+from channels.layers import get_channel_layer
+from django.conf import settings
 from django.core.exceptions import ValidationError
 from django.utils import timezone
 from strawberry.file_uploads import Upload
@@ -59,6 +62,18 @@ def _handle_form_errors(
                 )
 
 
+def notify_new_post(post: blog_models.Post) -> None:
+    channel_layer = get_channel_layer()
+    group_send = async_to_sync(channel_layer.group_send)  # type: ignore
+    group_send(
+        settings.POSTS_CHANNEL,
+        {
+            "type": "chat.message",
+            "post_id": post.pk,
+        },
+    )
+
+
 @strawberry.type
 class Mutation:
     @strawberry_django.mutation(
@@ -120,6 +135,8 @@ def publish_post(self, id: uuid.UUID) -> blog_types.Post:  # noqa: A002
             post.published = True
             post.published_at = timezone.now()
             post.save()
+
+        notify_new_post(post)
         return typing.cast(blog_types.Post, post)
 
     @strawberry_django.mutation(handle_django_errors=True)

server/app/blog/graph/subscriptions.py

@@ -0,0 +1,42 @@
+import typing
+
+import strawberry
+from channels.db import database_sync_to_async
+from django.conf import settings
+from strawberry.types import Info
+
+from server.app.blog import models as blog_models
+from server.app.blog.graph import types as blog_types
+
+
+@database_sync_to_async
+def _get_post(id: str) -> blog_models.Post | None:  # noqa: A002
+    try:
+        return blog_models.Post.objects.get(id=id)
+    except blog_models.Post.DoesNotExist:
+        return None
+
+
+@strawberry.type
+class Subscription:
+    @strawberry.subscription
+    async def post_notify(
+        self,
+        info: Info,
+    ) -> typing.AsyncGenerator[blog_types.PostNotification, None]:
+        ws = info.context["ws"]
+        channel_layer = ws.channel_layer
+        await channel_layer.group_add(settings.POSTS_CHANNEL, ws.channel_name)
+
+        async with ws.listen_to_channel(
+            "chat.message",
+            groups=[settings.POSTS_CHANNEL],
+        ) as cm:
+            async for message in cm:
+                post = await _get_post(message["post_id"])
+                if post:
+                    yield blog_types.PostNotification(
+                        id=post.pk,
+                        title=post.title,
+                        publish_at=post.published_at,
+                    )

server/app/blog/graph/types.py

@@ -140,3 +140,10 @@ class CreatePostResult:
             strawberry.union("FormValidationError"),
         ]
     ] | None = strawberry.field(default=None)
+
+
+@strawberry.type
+class PostNotification(relay.Node):
+    id: relay.NodeID[uuid.UUID]  # noqa: A003
+    title: str
+    publish_at: datetime.datetime

server/asgi.py

@@ -10,7 +10,16 @@
 import os
 
 from django.core.asgi import get_asgi_application
+from strawberry.channels import GraphQLProtocolTypeRouter
 
 os.environ.setdefault("DJANGO_SETTINGS_MODULE", "server.settings")
 
-application = get_asgi_application()
+django_asgi_app = get_asgi_application()
+
+from server.schema import ws_schema  # noqa: E402
+
+application = GraphQLProtocolTypeRouter(
+    ws_schema,
+    django_application=django_asgi_app,  # type: ignore
+    url_pattern="^wsgraphql",
+)

server/schema.py

@@ -5,6 +5,7 @@
 from server.app.authentication.graph import queries as auth_queries
 from server.app.blog.graph import mutations as blog_mutations
 from server.app.blog.graph import queries as blog_queries
+from server.app.blog.graph import subscriptions as blog_subscriptions
 
 __all__ = ("schema",)
 
@@ -23,6 +24,11 @@
         auth_mutations.Mutation,
     ),
 )
+subscription = strawberry.tools.merge_types(
+    "Subscription",
+    (blog_subscriptions.Subscription,),
+)
 
 
 schema = strawberry.Schema(query=query, mutation=mutation)
+ws_schema = strawberry.Schema(query=query, subscription=subscription)

server/settings.py

@@ -31,6 +31,7 @@
 # Application definition
 
 INSTALLED_APPS = [
+    "daphne",
     "django.contrib.admin",
     "django.contrib.auth",
     "django.contrib.contenttypes",
@@ -72,6 +73,7 @@
 ]
 
 WSGI_APPLICATION = "server.wsgi.application"
+ASGI_APPLICATION = "server.asgi.application"
 
 
 # Database
@@ -129,3 +131,11 @@
 # https://docs.djangoproject.com/en/4.2/ref/settings/#default-auto-field
 
 DEFAULT_AUTO_FIELD = "django.db.models.BigAutoField"
+
+CHANNEL_LAYERS = {
+    "default": {
+        "BACKEND": "channels.layers.InMemoryChannelLayer",
+    },
+}
+
+POSTS_CHANNEL = "posts_notifications"