From a2404e01cdbeef2ba332e147a5f2f1ca0a0310d7 Mon Sep 17 00:00:00 2001
From: Andrew Godwin
Date: Sat, 5 Nov 2022 22:49:25 -0600
Subject: Queuing system and lazy profile fetch

---
 miniq/views.py | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 miniq/views.py

(limited to 'miniq/views.py')

diff --git a/miniq/views.py b/miniq/views.py
new file mode 100644
index 0000000..12da7cd
--- /dev/null
+++ b/miniq/views.py
@@ -0,0 +1,68 @@
+import asyncio
+import time
+import traceback
+import uuid
+
+from asgiref.sync import sync_to_async
+from django.http import HttpResponse
+from django.views import View
+
+from miniq.models import Task
+from users.models import Identity
+
+
+class QueueProcessor(View):
+    """
+    A view that takes some items off the queue and processes them.
+    Tries to limit its own runtime so it's within HTTP timeout limits.
+    """
+
+    START_TIMEOUT = 30
+    TOTAL_TIMEOUT = 60
+    MAX_TASKS = 10
+
+    async def get(self, request):
+        start_time = time.monotonic()
+        processor_id = uuid.uuid4().hex
+        handled = 0
+        self.tasks = []
+        # For the first time period, launch tasks
+        while (time.monotonic() - start_time) < self.START_TIMEOUT:
+            # Remove completed tasks
+            self.tasks = [t for t in self.tasks if not t.done()]
+            # See if there's a new task
+            if len(self.tasks) < self.MAX_TASKS:
+                # Pop a task off the queue and run it
+                task = await sync_to_async(Task.get_one_available)(processor_id)
+                if task is not None:
+                    self.tasks.append(asyncio.create_task(self.run_task(task)))
+                    handled += 1
+            # Prevent busylooping
+            await asyncio.sleep(0.01)
+        # Then wait for tasks to finish
+        while (time.monotonic() - start_time) < self.TOTAL_TIMEOUT:
+            # Remove completed tasks
+            self.tasks = [t for t in self.tasks if not t.done()]
+            if not self.tasks:
+                break
+            # Prevent busylooping
+            await asyncio.sleep(1)
+        return HttpResponse(f"{handled} tasks handled")
+
+    async def run_task(self, task):
+        try:
+            print(f"Task {task}: Starting")
+            handler = getattr(self, f"handle_{task.type}", None)
+            if handler is None:
+                raise ValueError(f"Cannot handle type {task.type}")
+            await handler(task.subject, task.payload)
+            await task.complete()
+            print(f"Task {task}: Complete")
+        except BaseException as e:
+            print(f"Task {task}: Error {e}")
+            traceback.print_exc()
+            await task.fail(f"{e}\n\n" + traceback.format_exc())
+
+    async def handle_identity_fetch(self, subject, payload):
+        identity = await sync_to_async(Identity.by_handle)(subject)
+        await identity.fetch_details()
-- 
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