Python：在進程打印後多次打印到控制檯

Question

我有下面的python3程序，它創建一些工作進程並在我點擊ctrl-c時殺死它們。 在將SIGTERM發送到子進程之前，主控制檯在控制檯print('[W] aghhh ... %d' % self.pid)上打印一行。問題在於，對於給定的進程，該行會輸出多次。像這樣（實際控制檯輸出）：

[W] aghhh ... 15773 
[W] aghhh ... 15773 
[W] aghhh ... 15774 
[W] aghhh ... 15773 
[W] aghhh ... 15774 
[W] aghhh ... 15775 
[W] aghhh ... 15776 

問題：這怎麼可能？ 什麼是殺死兒童過程的正確方法？

代碼：

import os 
import time 
import signal 
import sys 


class ChildProcess: 
    def __init__(self, m): 
    self.pid = None 
    self.ttl = 10 
    self.master = m 
    self.pipe_in = None 
    self.pipe_out = None 

    def hey(self): 
    self.ttl -= 1 
    self.pipe_out.write('Hello worker %d\n' % self.pid) 
    self.pipe_out.flush() 

    def tell_me(self): 
    msg = self.pipe_in.readline() 
    print('[M] Worker process %d says: %s' % (self.pid, msg), end='') 

    def live(self): 
    r1, w1 = os.pipe() 
    r2, w2 = os.pipe() 
    pid = os.fork() 
    self.pid = pid 
    if pid: 
     print('[M] Created worker process %d' % pid) 
     os.close(w1) 
     os.close(r2) 
     self.pipe_in = os.fdopen(r1, 'rt') 
     self.pipe_out = os.fdopen(w2, 'wt') 
     self.master.add(self) 
    else: 
     print('[W] Worker process ready to rock') 
     os.close(r1) 
     os.close(w2) 
     wr = os.fdopen(w1, 'wt') 
     reader = os.fdopen(r2) 
     while True: 
     wr.write('Hello Master\n') 
     wr.flush() 
     msg = reader.readline() 
     print('[W] Master says %s' % msg, end='') 

    def die(self): 
    print('[W] aghhh ... %d' % self.pid) 
    os.kill(self.pid, signal.SIGTERM) 


class Master: 
    def __init__(self): 
    self.workers = [] 

    def add(self, worker): 
    self.workers.append(worker) 

    def rulez(self, nbr=2): 
    for i in range(nbr): 
     worker = ChildProcess(self) 
     worker.live() 
    while True: 
     for w in self.workers: 
     w.tell_me() 
     time.sleep(1) 
     w.hey() 

    def reap(self): 
    for w in self.workers: 
     w.die() 


if __name__ == '__main__': 
    master = Master() 

    try: 
    master.rulez(3) 
    except KeyboardInterrupt: 
    master.reap() 

Answer 1

這是因爲一個事實，即子進程正在執行相同的代碼如父。因此，對於子進程，當他們在執行while True: wr.write('Hello Master\n') …時，如果他們在被父進程殺死之前收到SIG_INT，他們會將KeyboardInterrupt提升爲調用方法，即master.rulez(3)。

所以，是的，實際上在master.rulez(3)中最多會有4 KeyboardInterrupt。您可以通過在except KeyboardInterrupt中打印某些內容來確認此問題，或者通過打印len(self.workers)來更好地進行確認。這會產生這樣的事情：

 
... 
[W] Master says Hello worker 769 
^C3 
2 
1 
[W] aghhh ... 769 
0 
[W] aghhh ... 769 
[W] aghhh ... 769 
[W] aghhh ... 770 
[W] aghhh ... 770 
[W] aghhh ... 771 

注意，當大師也許分叉其他孩子每個孩子分叉，所以也有在「self.workers」一些其他的孩子。所以對於第一個孩子，這將是空的，第二個孩子，這將是1，第三個孩子，這將是你的代碼的2

可視化（兩名工人）：

 
Master 
| 
| 
ChildProcess1 (init) 
| 
+---------------------+ (fork) 
|      | 
self.workers.add(1) While True: ... 
|      | 
|      (KeyboardInterrupt) 
|      master.reap() 
ChildProcess2 (init) (exit) 
| 
+---------------------+ (fork) <---- This copied self.workers also, which 
|      |    already contains ChildProcess1 
self.workers.add(2) While True: ... 
while True: ...  | 
(KeyboardInterrupt) (KeyboardInterrupt) 
master.reap()   master.reap() 
ChildProcess1.die() ChildProcess1.die() 
ChildProcess2.die() (exit) 
(exit) 

爲了防止從master.rulez(3)繼續執行的孩子，你可以趕上在子進程的KeyboardInterrupt，然後提高sys.exit()有（或者可以使用os.kill()也殺死自己）

代碼：

import os 
import time 
import signal 
import sys 


class ChildProcess: 
    def __init__(self, m): 
    self.pid = None 
    self.ttl = 10 
    self.master = m 
    self.pipe_in = None 
    self.pipe_out = None 

    def hey(self): 
    self.ttl -= 1 
    self.pipe_out.write('Hello worker %d\n' % self.pid) 
    self.pipe_out.flush() 

    def tell_me(self): 
    msg = self.pipe_in.readline() 
    print '[M] Worker process %d says: %s' % (self.pid, msg), 

    def live(self): 
    r1, w1 = os.pipe() 
    r2, w2 = os.pipe() 
    pid = os.fork() 
    self.pid = pid 
    if pid: 
     print('[M] Created worker process %d' % pid) 
     os.close(w1) 
     os.close(r2) 
     self.pipe_in = os.fdopen(r1, 'rt') 
     self.pipe_out = os.fdopen(w2, 'wt') 
     self.master.add(self) 
    else: 
     print('[W] Worker process ready to rock') 
     os.close(r1) 
     os.close(w2) 
     wr = os.fdopen(w1, 'wt') 
     reader = os.fdopen(r2) 
     try: 
     while True: 
      wr.write('Hello Master\n') 
      wr.flush() 
      msg = reader.readline() 
      print('[W] Master says %s' % msg), 
     except KeyboardInterrupt: 
     sys.exit() 

    def die(self): 
    print('[W] aghhh ... %d' % self.pid) 
    os.kill(self.pid, signal.SIGTERM) 


class Master: 
    def __init__(self): 
    self.workers = [] 

    def add(self, worker): 
    self.workers.append(worker) 

    def rulez(self, nbr=2): 
    for i in range(nbr): 
     worker = ChildProcess(self) 
     worker.live() 
    while True: 
     for w in self.workers: 
     w.tell_me() 
     time.sleep(1) 
     w.hey() 

    def reap(self): 
    print len(self.workers) 
    for w in self.workers: 
     w.die() 


if __name__ == '__main__': 
    master = Master() 

    try: 
    master.rulez(4) 
    except KeyboardInterrupt: 
    master.reap() 

結果：

 
... 
[W] Master says Hello worker 779 
^C3 
[W] aghhh ... 779 
[W] aghhh ... 780 
[W] aghhh ... 781