Molodetz blogrol volgens DPP-template

molodetz/services/queue.py

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+# retoor <retoor@molodetz.nl>
+import asyncio
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+class BackgroundQueue:
+    def __init__(self, max_size=10000):
+        self.max_size = max_size
+        self._queue = None
+        self._task = None
+
+    @property
+    def running(self):
+        return self._task is not None and not self._task.done()
+
+    def start(self):
+        if self.running:
+            return
+        self._queue = asyncio.Queue(maxsize=self.max_size)
+        self._task = asyncio.get_running_loop().create_task(self._consume())
+
+    def submit(self, fn, *args, **kwargs):
+        if not self.running:
+            self._run(fn, args, kwargs)
+            return
+        try:
+            self._queue.put_nowait((fn, args, kwargs))
+        except asyncio.QueueFull:
+            self._run(fn, args, kwargs)
+
+    async def stop(self):
+        if self._task is None:
+            return
+        self._task.cancel()
+        try:
+            await self._task
+        except asyncio.CancelledError:
+            pass
+        self._task = None
+        self.drain()
+
+    def drain(self):
+        if self._queue is None:
+            return
+        while not self._queue.empty():
+            fn, args, kwargs = self._queue.get_nowait()
+            self._run(fn, args, kwargs)
+
+    async def _consume(self):
+        while True:
+            fn, args, kwargs = await self._queue.get()
+            self._run(fn, args, kwargs)
+            self._queue.task_done()
+
+    @staticmethod
+    def _run(fn, args, kwargs):
+        try:
+            fn(*args, **kwargs)
+        except Exception:
+            logger.exception("background task %s failed", getattr(fn, "__name__", fn))
+
+
+background = BackgroundQueue()