Eventlet/Examples

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Examples

These are short examples demonstrating the use of Eventlet. They are also included in the examples directory of the source.

echo server

This is a simple server that listens on port 6000 and simply echoes back every input line it receives. Connect to it with: telnet localhost 6000 Terminate your connection by quitting telnet (typically Ctrl-] and then 'quit')

<python>from eventlet import api

def handle_socket(client):

   print "client connected"
   while True:
      # pass through every non-eof line
      x = client.readline()
      if not x: break
      client.write(x)
      print "echoed", x
  print "client disconnected"
  1. server socket listening on port 6000

server = api.tcp_listener(('0.0.0.0', 6000)) while True:

  new_sock, address = server.accept()
  # handle every new connection with a new coroutine
  api.spawn(handle_socket, new_sock)

server.close()</python>

web crawler

This is a simple web "crawler" that fetches a bunch of urls using a coroutine pool. It has as much concurrency (i.e. pages being fetched simultaneously) as coroutines in the pool.

<python>urls = ["http://www.google.com/intl/en_ALL/images/logo.gif",

       "http://wiki.secondlife.com/w/images/secondlife.jpg",
       "http://us.i1.yimg.com/us.yimg.com/i/ww/beta/y3.gif"]

import time from eventlet import coros, httpc, util

  1. replace socket with a cooperative coroutine socket because httpc
  2. uses httplib, which uses socket. Removing this serializes the http
  3. requests, because the standard socket is blocking.

util.wrap_socket_with_coroutine_socket()

def fetch(url):

   # we could do something interesting with the result, but this is
   # example code, so we'll just report that we did it
   print "%s fetching %s" % (time.asctime(), url)
   httpc.get(url)
   print "%s fetched %s" % (time.asctime(), url)

pool = coros.CoroutinePool(max_size=4) waiters = [] for url in urls:

   waiters.append(pool.execute(fetch, url))
  1. wait for all the coroutines to come back before exiting the process

for waiter in waiters:

   waiter.wait()</python>