eventlet绿化和patch原理

2020年11月21日 12:09

说明

 
eventlet是一个必备工具,经常用,绿化原理有点忘记了,重新复习一遍.
 
 

三个主要问题

 
1. 绿化的原理是什么?
 
2. 绿化怎么管理?
 
3. 绿化怎么引入?
 

绿化原理

 
利用select/epolls/kqueue等操作系统提供的非阻塞操作,将阻塞改为非阻塞.
 

引用管理

 
eventlet在import之后,将模块中的属性绿化.
 
用一小段代码来查看看
import sys
import eventlet
# eventlet.monkey_patch()

httplib2 = eventlet.import_patched('httplib2')
print(httplib2)
print(httplib2.socket)

print("================")
for k,v in sys.modules.items():
    if "socket" in k:
        print(k, v)


# 打印内容
<module 'httplib2' from 'D:\\workspace\\venv\\xxx\\lib\\site-packages\\httplib2\\__init__.py'>
<module 'eventlet.green.socket' from 'D:\\workspace\\venv\\xxx\\lib\\site-packages\\eventlet\\green\\socket.py'>
================
_socket <module '_socket' from 'c:\\python\\python36\\DLLs\\_socket.pyd'>
socket <module 'socket' from 'c:\\python\\python36\\lib\\socket.py'>
__original_module_socket <module 'socket' from 'c:\\python\\python36\\lib\\socket.py'>

# 说明了什么?
绿化只是替换httplib2模块中的引用属性socket。并未改变sys.modules中的属性
 

引入绿化方法一:直接import

 
from eventlet.green import socket
 

引入绿化方法二:eventlet.import_patch

 
1.好处: 能绿化模块内部的系统模块
2.只能绿化os, select, socket, thread, time, psycopy, MySQLdb, bultines, subprocess
3.如果是import threading,不会自动绿化, 需要from eventlet.green import threading
 
import eventlet
httplib2 = eventlet.import_patched('httplib2')
print(httplib2)
print(httplib2.socket)

# 打印
<module 'httplib2' from 'D:\\workspace\\venv\\autumn-secs\\lib\\site-packages\\httplib2\\__init__.py'>
<module 'eventlet.green.socket' from 'D:\\workspace\\venv\\autumn-secs\\lib\\site-packages\\eventlet\\green\\socket.py'>
 

引入绿化方法三:eventlet.monkey_patch

 
1.与import_patch不同,会直接修改sys.modules
2.但是也只能绿化os,select等等几个模块,其它模块需要用直接引用绿化
 
 
 

Tags: eventlet
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eventlet并发读写socket出现Second simultaneous问题

2020年7月08日 10:50

 

描述

 
celery+eventlet实现任务调用时出现RuntimeError: Second simultaneous read on fileno 14 detected.  Unless you really know what you're doing, make sure that only one greenthread can read any particular socket
 
 

模拟错误

 
网上找的一段代码,模拟出同样问题
 
def main():
    import eventlet
    httplib2 = eventlet.import_patched('httplib2')
    shared_resource = httplib2.Http()

    def get_url():
        resp, content = shared_resource.request("http://eventlet.net")
        return content

    p = eventlet.GreenPile()
    p.spawn(get_url)
    p.spawn(get_url)
    results = list(p)
    assert results[0] == results[1]


if __name__ == "__main__":
    main()
 

错误内容

 
Traceback (most recent call last):
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/eventlet/hubs/poll.py", line 111, in wait
    listener.cb(fileno)
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/eventlet/greenthread.py", line 221, in main
    result = function(*args, **kwargs)
  File "test.py", line 12, in get_url
    resp, content = shared_resource.request("http://eventlet.net")
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/httplib2/__init__.py", line 1994, in request
    cachekey,
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/httplib2/__init__.py", line 1651, in _request
    conn, request_uri, method, body, headers
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/httplib2/__init__.py", line 1558, in _conn_request
    conn.request(method, request_uri, body, headers)
  File "/root/miniconda3/envs/defect/lib/python3.7/http/client.py", line 1252, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/root/miniconda3/envs/defect/lib/python3.7/http/client.py", line 1298, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/root/miniconda3/envs/defect/lib/python3.7/http/client.py", line 1247, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/root/miniconda3/envs/defect/lib/python3.7/http/client.py", line 1026, in _send_output
    self.send(msg)
  File "/root/miniconda3/envs/defect/lib/python3.7/http/client.py", line 987, in send
    self.sock.sendall(data)
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/eventlet/greenio/base.py", line 403, in sendall
    tail = self.send(data, flags)
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/eventlet/greenio/base.py", line 397, in send
    return self._send_loop(self.fd.send, data, flags)
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/eventlet/greenio/base.py", line 392, in _send_loop
    timeout_exc=_timeout_exc)
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/eventlet/greenio/base.py", line 210, in _trampoline
    mark_as_closed=self._mark_as_closed)
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/eventlet/hubs/__init__.py", line 157, in trampoline
    listener = hub.add(hub.WRITE, fileno, current.switch, current.throw, mark_as_closed)
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/eventlet/hubs/epolls.py", line 22, in add
    listener = hub.BaseHub.add(self, evtype, fileno, cb, tb, mac)
  File "/root/miniconda3/envs/defect/lib/python3.7/site-packages/eventlet/hubs/hub.py", line 181, in add
    evtype, fileno, evtype, cb, bucket[fileno]))
RuntimeError: Second simultaneous write on fileno 5 detected.  Unless you really know what you're doing, make sure that only one greenthread can write any particular socket.  Consider using a pools.Pool. If you do know what you're doing and want to disable this error, call eventlet.debug.hub_prevent_multiple_readers(False) - MY THREAD=<built-in method switch of GreenThread object at 0x7f25df161680>; THAT THREAD=FdListener('write', 5, <built-in method switch of GreenThread object at 0x7f25df161470>, <built-in method throw of GreenThread object at 0x7f25df161470>)
 

 解决方法

 
猜测可能是没绿化完整,改成如下,果然就正常了。
 
def main():
    import eventlet
#     httplib2 = eventlet.import_patched('httplib2')
    import http2
    eventlet.monkey_patch()
    shared_resource = httplib2.Http()

    def get_url():
        resp, content = shared_resource.request("http://eventlet.net")
        return content

    p = eventlet.GreenPile()
    p.spawn(get_url)
    p.spawn(get_url)
    results = list(p)
    assert results[0] == results[1]


if __name__ == "__main__":
    main()
 

结论

  • 局部import的模块,可能使用了未被绿化的模块,导出eventlet出现问题
  • 延迟加载的模块配合eventlet也会出现同样问题
 

 

Tags: eventlet
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eventlet在ubuntu上出现OSError protocol not found

2020年6月21日 09:24

描述

 
tensorflow的nvidia docker镜像使用ubuntu16.04, ubuntu是精简之后的,有些包可能没有。在上面运行eventlet会出现下面问题
 
 

错误内容

 
Traceback (most recent call last):
  File "/app/defect-client/defect_client/cmd/wafer-worker.py", line 14, in <module>
    import eventlet
  File "/usr/local/lib/python3.6/dist-packages/eventlet/__init__.py", line 10, in <module>
    from eventlet import convenience
  File "/usr/local/lib/python3.6/dist-packages/eventlet/convenience.py", line 7, in <module>
    from eventlet.green import socket
  File "/usr/local/lib/python3.6/dist-packages/eventlet/green/socket.py", line 21, in <module>
    from eventlet.support import greendns
  File "/usr/local/lib/python3.6/dist-packages/eventlet/support/greendns.py", line 69, in <module>
    setattr(dns.rdtypes.IN, pkg, import_patched('dns.rdtypes.IN.' + pkg))
  File "/usr/local/lib/python3.6/dist-packages/eventlet/support/greendns.py", line 59, in import_patched
    return patcher.import_patched(module_name, **modules)
  File "/usr/local/lib/python3.6/dist-packages/eventlet/patcher.py", line 126, in import_patched
    *additional_modules + tuple(kw_additional_modules.items()))
  File "/usr/local/lib/python3.6/dist-packages/eventlet/patcher.py", line 100, in inject
    module = __import__(module_name, {}, {}, module_name.split('.')[:-1])
  File "/usr/local/lib/python3.6/dist-packages/dns/rdtypes/IN/WKS.py", line 25, in <module>
    _proto_tcp = socket.getprotobyname('tcp')
OSError: protocol not found
 

解决办法

 
apt-get -o Dpkg::Options::="--force-confmiss" install --reinstall netbase
 

Tags: eventlet python
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