protocols/logging: add LogForwarder

artiq/protocols/logging.py

@@ -2,6 +2,7 @@ import asyncio
 import logging
 
 from artiq.protocols.asyncio_server import AsyncioServer
+from artiq.tools import TaskObject
 
 
 _fwd_logger = logging.getLogger("fwd")
@@ -70,3 +71,39 @@ class Server(AsyncioServer):
                               extra={"source": source})
         finally:
             writer.close()
+
+
+class LogForwarder(logging.Handler, TaskObject):
+    def __init__(self, host, port, reconnect_timer=5.0, queue_size=1000,
+                 **kwargs):
+        logging.Handler.__init__(self, **kwargs)
+        self.host = host
+        self.port = port
+        self.setFormatter(logging.Formatter(
+            "%(source)s:%(levelno)d:%(name)s:%(message)s"))
+        self._queue = asyncio.Queue(queue_size)
+        self.reconnect_timer = reconnect_timer
+
+    def emit(self, record):
+        message = self.format(record)
+        try:
+            self._queue.put_nowait(message)
+        except asyncio.QueueFull:
+            pass
+
+    async def _do(self):
+        while True:
+            try:
+                reader, writer = await asyncio.open_connection(self.host,
+                                                               self.port)
+                writer.write(_init_string)
+                while True:
+                    message = await self._queue.get() + "\n"
+                    writer.write(message.encode())
+                    await writer.drain()
+            except asyncio.CancelledError:
+                return
+            except:
+                await asyncio.sleep(self.reconnect_timer)
+            finally:
+                writer.close()