Adding SSL version of the calculator example
- Used to test asyncio SSL on Windows mainly - Skipping asyncio thread tests on Windows (due to getTimer wrapper bug on Windows)
This commit is contained in:
Jacob Alexander
239
examples/async_ssl_calculator_server.py
Executable file
239
examples/async_ssl_calculator_server.py
Executable file
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#!/usr/bin/env python3
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import argparse
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import asyncio
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import logging
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import os
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import socket
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import ssl
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import capnp
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import calculator_capnp
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logger = logging.getLogger(__name__)
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logger.setLevel(logging.DEBUG)
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this_dir = os.path.dirname(os.path.abspath(__file__))
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class Server:
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async def myreader(self):
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while self.retry:
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try:
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# Must be a wait_for so we don't block on read()
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data = await asyncio.wait_for(
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self.reader.read(4096),
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timeout=0.1
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)
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except asyncio.TimeoutError:
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logger.debug("myreader timeout.")
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continue
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except Exception as err:
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logger.error("Unknown myreader err: %s", err)
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return False
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await self.server.write(data)
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logger.debug("myreader done.")
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return True
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async def mywriter(self):
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while self.retry:
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try:
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# Must be a wait_for so we don't block on read()
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data = await asyncio.wait_for(
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self.server.read(4096),
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timeout=0.1
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)
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self.writer.write(data.tobytes())
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except asyncio.TimeoutError:
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logger.debug("mywriter timeout.")
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continue
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except Exception as err:
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logger.error("Unknown mywriter err: %s", err)
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return False
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logger.debug("mywriter done.")
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return True
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async def myserver(self, reader, writer):
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# Start TwoPartyServer using TwoWayPipe (only requires bootstrap)
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self.server = capnp.TwoPartyServer(bootstrap=CalculatorImpl())
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self.reader = reader
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self.writer = writer
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self.retry = True
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# Assemble reader and writer tasks, run in the background
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coroutines = [self.myreader(), self.mywriter()]
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tasks = asyncio.gather(*coroutines, return_exceptions=True)
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while True:
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self.server.poll_once()
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# Check to see if reader has been sent an eof (disconnect)
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if self.reader.at_eof():
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self.retry = False
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break
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await asyncio.sleep(0.01)
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# Make wait for reader/writer to finish (prevent possible resource leaks)
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await tasks
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def read_value(value):
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'''Helper function to asynchronously call read() on a Calculator::Value and
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return a promise for the result. (In the future, the generated code might
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include something like this automatically.)'''
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return value.read().then(lambda result: result.value)
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def evaluate_impl(expression, params=None):
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'''Implementation of CalculatorImpl::evaluate(), also shared by
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FunctionImpl::call(). In the latter case, `params` are the parameter
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values passed to the function; in the former case, `params` is just an
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empty list.'''
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which = expression.which()
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if which == 'literal':
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return capnp.Promise(expression.literal)
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elif which == 'previousResult':
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return read_value(expression.previousResult)
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elif which == 'parameter':
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assert expression.parameter < len(params)
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return capnp.Promise(params[expression.parameter])
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elif which == 'call':
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call = expression.call
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func = call.function
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# Evaluate each parameter.
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paramPromises = [evaluate_impl(param, params) for param in call.params]
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joinedParams = capnp.join_promises(paramPromises)
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# When the parameters are complete, call the function.
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ret = (joinedParams
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.then(lambda vals: func.call(vals))
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.then(lambda result: result.value))
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return ret
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else:
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raise ValueError("Unknown expression type: " + which)
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class ValueImpl(calculator_capnp.Calculator.Value.Server):
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"Simple implementation of the Calculator.Value Cap'n Proto interface."
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def __init__(self, value):
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self.value = value
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def read(self, **kwargs):
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return self.value
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class FunctionImpl(calculator_capnp.Calculator.Function.Server):
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'''Implementation of the Calculator.Function Cap'n Proto interface, where the
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function is defined by a Calculator.Expression.'''
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def __init__(self, paramCount, body):
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self.paramCount = paramCount
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self.body = body.as_builder()
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def call(self, params, _context, **kwargs):
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'''Note that we're returning a Promise object here, and bypassing the
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helper functionality that normally sets the results struct from the
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returned object. Instead, we set _context.results directly inside of
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another promise'''
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assert len(params) == self.paramCount
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# using setattr because '=' is not allowed inside of lambdas
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return evaluate_impl(self.body, params).then(lambda value: setattr(_context.results, 'value', value))
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class OperatorImpl(calculator_capnp.Calculator.Function.Server):
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'''Implementation of the Calculator.Function Cap'n Proto interface, wrapping
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basic binary arithmetic operators.'''
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def __init__(self, op):
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self.op = op
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def call(self, params, **kwargs):
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assert len(params) == 2
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op = self.op
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if op == 'add':
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return params[0] + params[1]
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elif op == 'subtract':
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return params[0] - params[1]
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elif op == 'multiply':
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return params[0] * params[1]
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elif op == 'divide':
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return params[0] / params[1]
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else:
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raise ValueError('Unknown operator')
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class CalculatorImpl(calculator_capnp.Calculator.Server):
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"Implementation of the Calculator Cap'n Proto interface."
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def evaluate(self, expression, _context, **kwargs):
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return evaluate_impl(expression).then(lambda value: setattr(_context.results, 'value', ValueImpl(value)))
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def defFunction(self, paramCount, body, _context, **kwargs):
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return FunctionImpl(paramCount, body)
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def getOperator(self, op, **kwargs):
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return OperatorImpl(op)
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def parse_args():
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parser = argparse.ArgumentParser(usage='''Runs the server bound to the\
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given address/port ADDRESS. ''')
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parser.add_argument("address", help="ADDRESS:PORT")
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return parser.parse_args()
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async def new_connection(reader, writer):
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server = Server()
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await server.myserver(reader, writer)
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async def main():
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address = parse_args().address
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host = address.split(':')
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addr = host[0]
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port = host[1]
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# Setup SSL context
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ctx = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
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ctx.load_cert_chain(os.path.join(this_dir, 'selfsigned.cert'), os.path.join(this_dir, 'selfsigned.key'))
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# Handle both IPv4 and IPv6 cases
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try:
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print("Try IPv4")
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server = await asyncio.start_server(
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new_connection,
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addr, port,
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ssl=ctx,
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family=socket.AF_INET
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)
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except Exception:
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print("Try IPv6")
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server = await asyncio.start_server(
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new_connection,
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addr, port,
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ssl=ctx,
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family=socket.AF_INET6
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)
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async with server:
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await server.serve_forever()
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if __name__ == '__main__':
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asyncio.run(main())
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