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Add examples back in

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Jason Paryani
2013-12-11 00:27:01 -08:00
parent db2247e883
commit 117a3c7eac
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274
examples/calculator_client.py Executable file
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#!/usr/bin/env python
from __future__ import print_function
import argparse
import socket
import capnp
import calculator_capnp
class PowerFunction(calculator_capnp.Calculator.Function.Server):
'''An implementation of the Function interface wrapping pow(). Note that
we're implementing this on the client side and will pass a reference to
the server. The server will then be able to make calls back to the client.'''
def call(self, params, **kwargs):
'''Note the **kwargs. This is very necessary to include, since protocols can add parameters over time. Also, by default, a _context variable is passed to all server methods. Read the docs for further explanation.'''
return pow(params[0], params[1])
def parse_args():
parser = argparse.ArgumentParser(usage='Connects to the Calculator server at the given address and does some RPCs')
parser.add_argument("host", help="HOST:PORT")
return parser.parse_args()
def main(sock):
client = capnp.TwoPartyClient(sock)
# Pass "calculator" to ez_restore (there's also a `restore` function that takes a struct or AnyPointer as an argument), and then cast the returned capability to it's proper type. This casting is due to capabilities not having a reference to their schema
calculator = client.ez_restore('calculator').cast_as(calculator_capnp.Calculator)
'''Make a request that just evaluates the literal value 123.
What's interesting here is that evaluate() returns a "Value", which is
another interface and therefore points back to an object living on the
server. We then have to call read() on that object to read it.
However, even though we are making two RPC's, this block executes in
*one* network round trip because of promise pipelining: we do not wait
for the first call to complete before we send the second call to the
server.'''
print('Evaluating a literal... ', end="")
# Set up the request. Note the form is 'evaluate' + '_request', where 'evaluate' is the name of the method we want to call
request = calculator.evaluate_request()
request.expression.literal = 123
# Send it, which returns a promise for the result (without blocking).
eval_promise = request.send()
# Using the promise, create a pipelined request to call read() on the returned object. Note that here we are using the shortened method call syntax read(), which is mostly just sugar for read_request().send()
read_promise = eval_promise.value.read()
# Now that we've sent all the requests, wait for the response. Until this
# point, we haven't waited at all!
response = read_promise.wait()
assert response.value == 123
print("PASS")
'''Make a request to evaluate 123 + 45 - 67.
# //
The Calculator interface requires that we first call getOperator() to
get the addition and subtraction functions, then call evaluate() to use
them. But, once again, we can get both functions, call evaluate(), and
then read() the result -- four RPCs -- in the time of *one* network
round trip, because of promise pipelining.'''
print("Using add and subtract... ", end='')
# Get the "add" function from the server.
add = calculator.getOperator(op='add').func
# Get the "subtract" function from the server.
subtract = calculator.getOperator(op='subtract').func
# Build the request to evaluate 123 + 45 - 67.
request = calculator.evaluate_request()
subtract_call = request.expression.init('call')
subtract_call.function = subtract
subtract_params = subtract_call.init('params', 2)
subtract_params[1].literal = 67.0
add_call = subtract_params[0].init('call')
add_call.function = add
add_params = add_call.init('params', 2)
add_params[0].literal = 123
add_params[1].literal = 45
# Send the evaluate() request, read() the result, and wait for read() to finish.
eval_promise = request.send()
read_promise = eval_promise.value.read()
response = read_promise.wait()
assert response.value == 101
print("PASS")
'''Make a request to evaluate 4 * 6, then use the result in two more
requests that add 3 and 5.
Since evaluate() returns its result wrapped in a `Value`, we can pass
that `Value` back to the server in subsequent requests before the first
`evaluate()` has actually returned. Thus, this example again does only
one network round trip.'''
print("Pipelining eval() calls... ", end="")
# Get the "add" function from the server.
add = calculator.getOperator(op='add').func
# Get the "multiply" function from the server.
multiply = calculator.getOperator(op='multiply').func
# Build the request to evaluate 4 * 6
request = calculator.evaluate_request()
multiply_call = request.expression.init("call")
multiply_call.function = multiply
multiply_params = multiply_call.init("params", 2);
multiply_params[0].literal = 4
multiply_params[1].literal = 6
multiply_result = request.send().value
# Use the result in two calls that add 3 and add 5.
add3Request = calculator.evaluate_request()
add3Call = add3Request.expression.init("call")
add3Call.function = add
add3Params = add3Call.init("params", 2)
add3Params[0].previousResult = multiply_result
add3Params[1].literal = 3
add3Promise = add3Request.send().value.read()
add5Request = calculator.evaluate_request()
add5Call = add5Request.expression.init("call")
add5Call.function = add
add5Params = add5Call.init("params", 2)
add5Params[0].previousResult = multiply_result
add5Params[1].literal = 5
add5Promise = add5Request.send().value.read()
# Now wait for the results.
assert add3Promise.wait().value == 27
assert add5Promise.wait().value == 29
print("PASS")
'''Our calculator interface supports defining functions. Here we use it
to define two functions and then make calls to them as follows:
f(x, y) = x * 100 + y
g(x) = f(x, x + 1) * 2;
f(12, 34)
g(21)
Once again, the whole thing takes only one network round trip.'''
print("Defining functions... ", end="")
# Get the "add" function from the server.
add = calculator.getOperator(op='add').func
# Get the "multiply" function from the server.
multiply = calculator.getOperator(op='multiply').func
# Define f.
request = calculator.defFunction_request()
request.paramCount = 2
# Build the function body.
addCall = request.body.init("call")
addCall.function = add
addParams = addCall.init("params", 2)
addParams[1].parameter = 1 # y
multiplyCall = addParams[0].init("call")
multiplyCall.function = multiply
multiplyParams = multiplyCall.init("params", 2)
multiplyParams[0].parameter = 0 # x
multiplyParams[1].literal = 100
f = request.send().func
# Define g.
request = calculator.defFunction_request()
request.paramCount = 1
# Build the function body.
multiplyCall = request.body.init("call")
multiplyCall.function = multiply
multiplyParams = multiplyCall.init("params", 2)
multiplyParams[1].literal = 2
fCall = multiplyParams[0].init("call")
fCall.function = f
fParams = fCall.init("params", 2)
fParams[0].parameter = 0
addCall = fParams[1].init("call")
addCall.function = add
addParams = addCall.init("params", 2)
addParams[0].parameter = 0
addParams[1].literal = 1
g = request.send().func
# OK, we've defined all our functions. Now create our eval requests.
# f(12, 34)
fEvalRequest = calculator.evaluate_request()
fCall = fEvalRequest.expression.init("call")
fCall.function = f
fParams = fCall.init("params", 2)
fParams[0].literal = 12
fParams[1].literal = 34
fEvalPromise = fEvalRequest.send().value.read()
# g(21)
gEvalRequest = calculator.evaluate_request()
gCall = gEvalRequest.expression.init("call")
gCall.function = g
gCall.init('params', 1)[0].literal = 21
gEvalPromise = gEvalRequest.send().value.read()
# Wait for the results.
assert fEvalPromise.wait().value == 1234
assert gEvalPromise.wait().value == 4244
print("PASS")
'''Make a request that will call back to a function defined locally.
Specifically, we will compute 2^(4 + 5). However, exponent is not
defined by the Calculator server. So, we'll implement the Function
interface locally and pass it to the server for it to use when
evaluating the expression.
This example requires two network round trips to complete, because the
server calls back to the client once before finishing. In this
particular case, this could potentially be optimized by using a tail
call on the server side -- see CallContext::tailCall(). However, to
keep the example simpler, we haven't implemented this optimization in
the sample server.'''
print("Using a callback... ", end="")
# Get the "add" function from the server.
add = calculator.getOperator(op='add').func
# Build the eval request for 2^(4+5).
request = calculator.evaluate_request()
powCall = request.expression.init("call")
powCall.function = PowerFunction()
powParams = powCall.init("params", 2)
powParams[0].literal = 2
addCall = powParams[1].init("call")
addCall.function = add
addParams = addCall.init("params", 2)
addParams[0].literal = 4
addParams[1].literal = 5
# Send the request and wait.
response = request.send().value.read().wait()
assert response.value == 512
print("PASS")
if __name__ == '__main__':
host, port = parse_args().host.split(':')
sock = socket.create_connection((host, port))
main(sock)

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examples/calculator_server.py Executable file
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#!/usr/bin/env python
from __future__ import print_function
import argparse
import socket
import random
import capnp
import calculator_capnp
def readValue(value):
'''Helper function to asynchronously call read() on a Calculator::Value and
return a promise for the result. (In the future, the generated code might
include something like this automatically.)'''
return value.read().then(lambda result: result.value)
def evaluateImpl(expression, params=None):
'''Implementation of CalculatorImpl::evaluate(), also shared by
FunctionImpl::call(). In the latter case, `params` are the parameter
values passed to the function; in the former case, `params` is just an
empty list.'''
which = expression.which()
if which == 'literal':
return capnp.Promise(expression.literal)
elif which == 'previousResult':
return readValue(expression.previousResult)
elif which == 'parameter':
assert expression.parameter < len(params)
return capnp.Promise(params[expression.parameter])
elif which == 'call':
def then(vals):
ret = func.call(vals).then(lambda result: result.value)
return ret
call = expression.call
func = call.function
# Evaluate each parameter.
paramPromises = [evaluateImpl(param, params) for param in call.params]
joinedParams = capnp.join_promises(paramPromises)
# When the parameters are complete, call the function.
ret = joinedParams.then(then)
return ret
else:
raise ValueError("Unknown expression type: " + which)
class ValueImpl(calculator_capnp.Calculator.Value.Server):
"Simple implementation of the Calculator.Value Cap'n Proto interface."
def __init__(self, value):
self.value = value
def read(self, **kwargs):
return self.value
class FunctionImpl(calculator_capnp.Calculator.Function.Server):
'''Implementation of the Calculator.Function Cap'n Proto interface, where the
function is defined by a Calculator.Expression.'''
def __init__(self, paramCount, body, obj):
self.paramCount = paramCount
self.body = body.as_builder()
self.obj = obj
def call(self, params, _context, **kwargs):
assert len(params) == self.paramCount
return evaluateImpl(self.body, params).then(lambda value: setattr(_context.results, 'value', value)) # using setattr because '=' is not allowed inside of lambdas
class OperatorImpl(calculator_capnp.Calculator.Function.Server):
'''Implementation of the Calculator.Function Cap'n Proto interface, wrapping
basic binary arithmetic operators.'''
def __init__(self, op):
self.op = op
def call(self, params, **kwargs):
assert len(params) == 2
op = self.op
if op == 'add':
return params[0] + params[1]
elif op == 'subtract':
return params[0] - params[1]
elif op == 'multiply':
return params[0] * params[1]
elif op == 'divide':
return params[0] / params[1]
else:
raise ValueError('Unknown operator')
class CalculatorImpl(calculator_capnp.Calculator.Server):
"Implementation of the Calculator Cap'n Proto interface."
def evaluate(self, expression, _context, **kwargs):
return evaluateImpl(expression).then(lambda value: setattr(_context.results, 'value', ValueImpl(value)))
def defFunction(self, paramCount, body, _context, **kwargs):
return FunctionImpl(paramCount, body, _context)
def getOperator(self, op, **kwargs):
return OperatorImpl(op)
def parse_args():
parser = argparse.ArgumentParser(usage='''Runs the server bound to the given address/port
ADDRESS may be '*' to bind to all local addresses.
:PORT may be omitted to choose a port automatically.
''')
parser.add_argument("address", help="ADDRESS[:PORT]")
return parser.parse_args()
class CalcRestorer:
def __init__(self):
self.calc = CalculatorImpl()
def restore(self, ref):
assert ref.as_text() == 'calculator'
return CalculatorImpl()
def main():
address = parse_args().address
if ':' in address:
address, port = address.split(':')
port = int(port)
else:
port = random.randint(60000,61000)
if address == '*':
address = ''
print("Listening on port: {}".format(port))
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((address,port))
s.listen(1) # service only 1 client at a time
while True:
try:
(clientsocket, address) = s.accept()
restorer = CalcRestorer()
server = capnp.TwoPartyServer(clientsocket, restorer)
server.run_forever()
print("client disconnected")
except KeyboardInterrupt:
break
if __name__ == '__main__':
main()