A Scalable Webserver

Contents:

• A Scalable Webserver
• Answer request on port 8080
• Adding a Hello World service
• Adding More Services
• Adding a Service Dispatcher
• Adding a pool of HTTPsocket processes

Answer request on port 8080

import pycsp

@pycsp.process
def HTTPsocket(sock):
    answer= 'HTTP/1.0...'

    conn, addr=sock
    req=conn.recv(256)
    if req:
        lines = req.split('\n')
        for line in lines:
            line=line.split(' ')
            if line[0]=='GET':
                conn.sendall(answer)
                conn.sendall("Hello from HTTPSocket");

    conn.shutdown(socket.SHUT_RDWR)
    conn.close()

@pycsp.process
def Entry():
    serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    serversocket.bind(('', 8080))
    serversocket.listen(1)
    while True:
        s = serversocket.accept()
        pycsp.Spawn( HTTPsocket(s) )

pycsp.Parallel( Entry() )

Adding a Hello World service

import pycsp

@pycsp.process
def HelloWorld(request):
    while True:
        (request_string, cout) = request()
        cout("Hello World at "+time.strftime("%H:%M:%S",  \\ time.localtime()))

@pycsp.process
def HTTPsocket(sock, sendRequest):
 [snip]
    for line in lines:
        line=line.split(' ')
        if line[0]=='GET':
            conn.sendall(answer)
            sendRequest((line[1], itemOut))
            conn.sendall(itemIn())
 [snip]

@pycsp.process
def Entry(dispatch):
    serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    serversocket.bind(('', int(sys.argv[1])))
    serversocket.listen(1)
    while True:
        s = serversocket.accept()
        pycsp.Spawn( HTTPsocket(s, dispatch) )

requestChan = pycsp.Channel('Request')

pycsp.Parallel( 
    Entry(requestChan.writer()),
    HelloWorld(requestChan.reader())
    )

Adding More Services

import pycsp

@pycsp.process
def Sleep5sec(id, request):
    seconds = 5 
    while True:
        (request_string, cout) = request()
        s = "Process " + str(id)
        s += " is going to sleep for " +str(seconds) + " seconds"
        cout(s)
        time.sleep(seconds)

pycsp.Parallel( 
    Entry(requestChan.writer()),
    [ Sleep5sec(id, requestChan.reader()) for id in range(3) ]
    )

Adding a Service Dispatcher

import pycsp

@pycsp.process
def HelloWorld(register):
    req = pycsp.Channel()
    cin = req.reader()
    register(('/hello.html', req.writer()))
    while True:
        (request_string, cout) = cin()
        cout("Hello World at " + time.strftime("%H:%M:%S", time.localtime()))

@pycsp.process
def Dispatcher(register, incoming_request):
    services = {}
    while True:
        pycsp.AltSelect(
           pycsp.InputGuard(register, action=add_service(services)),
           pycsp.InputGuard(incoming_request,
					action=dispatch(services))
        )

@pycsp.choice
def add_service(services, channel_input=None):
    (id, requestChEnd) = channel_input
    if services.has_key(id):
        services[id].append(requestChEnd)
    else:
        services[id] = [requestChEnd]

@pycsp.choice
def dispatch(services, channel_input = None):
    (GET, resultChEnd) = channel_input
    if GET.find('?') != -1:
        service_id = GET[:GET.index('?')]
    else:
        service_id = GET

    # Dispatch to service by Alting on output ends.
    if services.has_key(service_id):
        guards = []
        for req in services[service_id]:
            guards.append( OutputGuard(req, msg=(GET, resultChEnd)) )
        pycsp.AltSelect(*guards)
    else:
        resultChEnd("Service '"+str(service_id)+"' not found!<br>")

pycsp.Parallel( 
    Entry(requestChan.writer()),
    Dispatcher(registerChan.reader(), requestChan.reader()),
    [ Sleep5sec(id, registerChan.writer()) for id in range(3) ],
    [Index(id, registerChan.writer()) for id in range(2)],
    HelloWorld(registerChan.writer()))

Adding a pool of HTTPsocket processes

import pycsp

@pycsp.process
def HTTPsocket(getSocket, sendRequest):
    [snip]
    while True:
        conn, addr= getSocket()
        req=conn.recv(256)
        if not req:
            conn.close()
            return
        lines = req.split('\n')
        for line in lines:
            line=line.split(' ')
            if line[0]=='GET':
                conn.sendall(answer)
                sendRequest((line[1], itemOut))
                conn.sendall(itemIn())

@pycsp.process
def Entry(dispatch):
    serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    serversocket.bind(('', int(sys.argv[1])))
    serversocket.listen(1)

    socketChan = pycsp.Channel('Socket Channel')
    sendSocket = socketChan.writer()
    
    pycsp.Spawn(
        [ HTTPsocket(socketChan.reader(), dispatch) for i in range(8) ]
        )

    while True:
        s = serversocket.accept()
        sendSocket(s)