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128 lines
4.4 KiB
128 lines
4.4 KiB
# Copyright (c) 2017, Neil Booth
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#
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# All rights reserved.
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#
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# See the file "LICENCE" for information about the copyright
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# and warranty status of this software.
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import asyncio
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import os
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import signal
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import sys
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import time
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from functools import partial
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import lib.util as util
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class ServerBase(util.LoggedClass):
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'''Base class server implementation.
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Derived classes are expected to:
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- set PYTHON_MIN_VERSION and SUPPRESS_MESSAGES as appropriate
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- implement the start_servers() coroutine, called from the run() method.
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Upon return the event loop runs until the shutdown signal is received.
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- implement the shutdown() coroutine
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'''
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SUPPRESS_MESSAGES = [
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'Fatal read error on socket transport',
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'Fatal write error on socket transport',
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]
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PYTHON_MIN_VERSION = (3, 6)
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def __init__(self, env):
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'''Save the environment, perform basic sanity checks, and set the
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event loop policy.
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'''
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super().__init__()
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self.env = env
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# Sanity checks
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if sys.version_info < self.PYTHON_MIN_VERSION:
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mvs = '.'.join(str(part) for part in self.PYTHON_MIN_VERSION)
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raise RuntimeError('Python version >= {} is required'.format(mvs))
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if os.geteuid() == 0 and not env.allow_root:
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raise RuntimeError('RUNNING AS ROOT IS STRONGLY DISCOURAGED!\n'
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'You shoud create an unprivileged user account '
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'and use that.\n'
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'To continue as root anyway, restart with '
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'environment variable ALLOW_ROOT non-empty')
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# First asyncio operation must be to set the event loop policy
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# as this replaces the event loop
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self.logger.info('event loop policy: {}'.format(self.env.loop_policy))
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asyncio.set_event_loop_policy(self.env.loop_policy)
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# Trigger this event to cleanly shutdown
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self.shutdown_event = asyncio.Event()
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async def start_servers(self):
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'''Override to perform initialization that requires the event loop,
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and start servers.'''
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pass
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async def shutdown(self):
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'''Override to perform the shutdown sequence, if any.'''
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pass
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async def _wait_for_shutdown_event(self):
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'''Wait for shutdown to be signalled, and log it.
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Derived classes may want to provide a shutdown() coroutine.'''
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# Shut down cleanly after waiting for shutdown to be signalled
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await self.shutdown_event.wait()
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self.logger.info('shutting down')
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# Wait for the shutdown sequence
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await self.shutdown()
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# Finally, work around an apparent asyncio bug that causes log
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# spew on shutdown for partially opened SSL sockets
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try:
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del asyncio.sslproto._SSLProtocolTransport.__del__
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except Exception:
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pass
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self.logger.info('shutdown complete')
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def on_signal(self, signame):
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'''Call on receipt of a signal to cleanly shutdown.'''
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self.logger.warning('received {} signal, initiating shutdown'
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.format(signame))
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self.shutdown_event.set()
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def on_exception(self, loop, context):
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'''Suppress spurious messages it appears we cannot control.'''
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message = context.get('message')
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if message in self.SUPPRESS_MESSAGES:
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return
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if 'accept_connection2()' in repr(context.get('task')):
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return
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loop.default_exception_handler(context)
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def run(self):
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'''Run the server application:
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- record start time
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- set the event loop policy as specified by the environment
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- install SIGINT and SIGKILL handlers to trigger shutdown_event
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- set loop's exception handler to suppress unwanted messages
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- run the event loop until start_servers() completes
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- run the event loop until shutdown is signalled
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'''
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self.start_time = time.time()
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loop = asyncio.get_event_loop()
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for signame in ('SIGINT', 'SIGTERM'):
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loop.add_signal_handler(getattr(signal, signame),
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partial(self.on_signal, signame))
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loop.set_exception_handler(self.on_exception)
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loop.run_until_complete(self.start_servers())
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loop.run_until_complete(self._wait_for_shutdown_event())
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loop.close()
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