Question

我使用eventlet跟随两个版本的代码。期望是2个spawn_n调用将同时执行，但事实并非如此。执行是连续发生的。

import eventlet
import threading
import datetime
from eventlet.green import urllib2


def hello(name):
    print eventlet.greenthread.getcurrent(), threading.current_thread()
    print datetime.datetime.now()
    print " %s hello !!" % name
    urllib2.urlopen("http://www.google.com/intl/en_ALL/images/logo.gif").read()

eventlet.spawn(hello, 'abc')
eventlet.spawn(hello, 'xyz')
eventlet.sleep(0)

O / P：＆lt; _MainThread（MainThread，启动140365670881088）＆gt;

2016-08-09 14：04：57.782866
abc你好!!
＆lt; _MainThread（MainThread，启动140365670881088）＆gt;
2016-08-09 14：05：02.929903
xyz你好!!

import eventlet
import threading
import datetime
from eventlet.green import urllib2


def hello(name):
    print eventlet.greenthread.getcurrent(), threading.current_thread()
    print datetime.datetime.now()
    print " %s hello !!" % name
    urllib2.urlopen("http://www.google.com/intl/en_ALL/images/logo.gif").read()

pool = eventlet.GreenPool(size=4)
pool.spawn_n(hello, 'pqr')
pool.spawn_n(hello, 'lmn')
pool.waitall()

O / P：＆lt; _MainThread（MainThread，启动139897149990720）＆gt;

2016-08-09 14：05：25.613546
pqr你好!!
＆lt; _MainThread（MainThread，启动139897149990720）＆gt;
2016-08-09 14：05：30.699473
你好！

在两个版本的代码中，调用按顺序进行。

Answer 1

def fun(tag):
  print('{0} begin'.format(tag))
  eventlet.sleep(0.1)  # pretty much the same as running HTTP request and throwing results away
  print('{0} end'.format(tag))

t1 = time.time()
pool.spawn(fun, 'Turtle')
pool.spawn(fun, 'Achilles')
pool.waitall()
tt = time.time() - t1
print('Total time: {0:.2f}'.format(tt))

你会看到类似的输出：

Turtle begin
Achilles begin
Turtle end
Achilles end
Total time: 0.10

这表明函数的执行在IO等待点（休眠）处交错，这接近于协同并发的定义。另请注意，总时间不是两次睡眠的总和，而是最大+基础设施开销（在此综合测试中应该几乎没有）。

有问题的代码无法显示这一点，因为您在IO之前只有打印（在Eventlet中不创建IO等待），之后没有。所以你实际执行的是：

main: pool.waitall() begin, switch to Eventlet loop
loop: oh, there are greenthreads scheduled to run now, switch to 1
1: print this
1: print that
1: urllib... start network IO, switch to loop
loop: there is another green thread scheduled, switch to 2
2: print this
2: print that
2: urllib... start network IO, switch to Eventlet loop
loop: wait for any event that should wake greenthread,
  suppose that would be thread 1 urllib that is finished first
1: HTTP request finished, thread 1 finished, but no code to prove it
loop: wait for any event...
2: HTTP request finished, thread 2 finished
main: pool.waitall() finished

Python Eventlet不会并发执行

1 个答案: