add examples/dns_mass_resolve.py

examples/dns_mass_resolve.py

+#!/usr/bin/python
+"""Resolve hostnames concurrently, exit after 2 seconds.
+
+Note, that gevent.socket.gethostname uses libevent-dns under the hood
+and yields the control to other greenlets until the result is ready.
+This script splits the job between a number of greenlets to get the
+results faster.
+"""
+
+from gevent import socket
+from gevent import pool
+
+N = 1000
+
+# limit ourselves to max 10 simultaneous outstanding requests
+p = pool.Pool(10)
+
+finished = 0
+
+def job(url):
+    global succeed, finished
+    try:
+        ip = socket.gethostbyname(url)
+        print '%s = %s' % (url, ip)
+    except socket.gaierror, ex:
+        print '%s failed with %s' % (url, ex)
+    finally:
+        finished += 1
+
+for x in xrange(10, N):
+    p.spawn(job, '%s.com' % x)
+
+p.join(timeout=2)
+print 'finished within 2 seconds: %s/%s' % (finished, N)