added an asyncio server example

Can't get the async handler to work.

Author: evvaaaa

example/asyncio_server.py

@@ -0,0 +1,120 @@
+#!/usr/bin/env python
+"""Demo server for demonstrating async handlers.
+
+   $ python example/asyncio_server.py foo
+
+"""
+
+from __future__ import print_function
+
+import time
+import logging
+import argparse
+import asyncio
+from p4p.server import StaticProvider, Server
+from p4p.server.asyncio import SharedPV
+from p4p.nt import NTScalar
+
+
+DEFAULT_TIMEOUT = 1
+
+class SomeClassWithACoroutine:
+    def __init__(self):
+        self.data = None
+
+    async def coroutine(self, value: str):
+        logging.info(f"Updating {self} from value {self.data} to {value}.")
+
+
+class AttrWHandler:
+    def __init__(self, some_object_with_coro: SomeClassWithACoroutine):
+        self.some_object_with_coro = some_object_with_coro
+
+    async def put(self, pv, op):
+        raw_value = op.value()
+        logging.info(f"Received put on {raw_value} to {pv.name()}.")
+
+        await self.some_object_with_coro.coroutine(raw_value)
+
+        pv.post(raw_value, timestamp=time.time())
+        op.done()
+
+
+class AsyncProviderWrapper:
+    def __init__(self, name: str, loop: asyncio.AbstractEventLoop):
+        self.name = name
+        self._loop = loop
+        self._provider = StaticProvider(name)
+        self._pvs = []
+
+        self.setUp()
+
+    async def asyncSetUp(self):
+        await self.add_pvs()
+
+    async def asyncTearDown(self): ...
+
+    async def add_pvs(self):
+
+        write_pv = SharedPV(
+            handler=AttrWHandler(SomeClassWithACoroutine()),
+            nt=NTScalar("s"),
+            initial="initial_value_1",
+        )
+        self._pvs.append(write_pv)
+        logging.info(f"Added {self.name}:WRITE_PV to provider.")
+        self._provider.add(f"{self.name}:WRITE_PV", write_pv)
+
+        read_pv = SharedPV(
+            nt=NTScalar("s"),
+            initial="initial_value_2",
+        )
+        self._pvs.append(read_pv)
+        logging.info(f"Added {self.name}:READ_PV to provider.")
+        self._provider.add(f"{self.name}:READ_PV", read_pv)
+
+    def setUp(self):
+        self._loop.set_debug(True)
+        self._loop.run_until_complete(asyncio.wait_for(self.asyncSetUp(), DEFAULT_TIMEOUT))
+
+    def tearDown(self):
+        self._loop.run_until_complete(asyncio.wait_for(self.asyncTearDown(), DEFAULT_TIMEOUT))
+
+
+class AsyncServerWrapper:
+    def __init__(
+        self,
+        pv_prefix: str,
+    ):
+        self._pv_prefix = pv_prefix
+        self._pvs = []
+
+    def run(self):
+        loop = asyncio.new_event_loop()
+        self.provider = AsyncProviderWrapper(self._pv_prefix, loop)
+        try:
+            loop.run_until_complete(self._run())
+        finally:
+            loop.close()
+
+    async def _run(self) -> None:
+        logging.info("Running server.")
+        try:
+            Server.forever(providers=[self.provider._provider])
+        finally:
+            print("Server stopped.")
+
+
+def main(args: argparse.Namespace):
+    AsyncServerWrapper(args.name).run()
+
+def getargs() -> argparse.Namespace:
+    P = argparse.ArgumentParser()
+    P.add_argument('prefix', type=str)
+    P.add_argument('-v','--verbose', action='store_const', default=logging.INFO, const=logging.DEBUG)
+    return P.parse_args()
+
+if __name__=='__main__':
+    args = getargs()
+    logging.basicConfig(level=args.verbose)
+    main(args)