爬虫之多线程 多进程 自定义异步IO框架

什么是进程？

进程是程序运行的实例，是系统进行资源分配和调度的一个独立单位，它包括独立的地址空间，资源以及1个或多个线程。

什么是线程？

线程可以看成是轻量级的进程，是CPU调度和分派的基本单位。

进程和线程的区别？

1.调度 ：从上面的定义可以看出一个是调度和分派的基本单位，一个是拥有资源的基本单位

2.共享地址空间，资源：进程拥有各自独立的地址空间，资源，所以共享复杂，需要用IPC，同步简单； 线程共享所属进程的资源，共享简单，但同步复杂，要通过加锁等措施。

3.占用内存，cpu: 进程占用内存多，切换复杂，CPU利用率低； 线程占用内存少，切换简单，CPU利用率高。

4.相互影响： 进程间不会相互影响； 一个线程挂掉会导致整个进程挂掉

应用场景？
计算型：就用进程，CPython有一个ＧIＬ锁 (GIL全称Global Interpreter Lock)，同一时刻，只能使用一个进程使用。

IO密集型：就用线程，因为ＩＯ操作不通过CPU。

非常有趣的解释了什么是进程和线程

参考博客：http://www.ruanyifeng.com/blog/2013/04/processes_and_threads.html

同步和异步的概念

同步是指用户线程发起IO请求后需要等待或者轮询内核IO操作完成后才能继续执行。

异步是指用户线程发起IO请求后仍继续执行，当内核IO操作完成后会通知用户线程，或者调用用户线程注册的回调函数。

阻塞和非阻塞的概念

阻塞是指IO操作需要彻底完成后才返回到用户空间。

非阻塞是指IO操作被调用后立即返回给用户一个状态值，无需等到IO操作彻底完成。

一、多线程

可以实现并发
但是，请求发送出去后和返回之前，中间时期线程空闲
编写方式：
- 直接返回处理
- 通过回调函数处理

方法一：

#!/usr/bin/env python
# -*- coding:utf-8 -*- 
# Author: nulige
#线程

from concurrent.futures import ThreadPoolExecutor
import requests
import time

def task(rul):
    response = requests.get(url)
    print(url, response)

pool = ThreadPoolExecutor(6)

url_list = [
    'http://huaban.com/favorite/beauty/',
    'https://www.bing.com/',
    'https://www.baidu.com/',
    'https://www.sina.com/',
    'https://www.zhihu.com/',
    'https://www.tencent.com/',
]

for url in url_list:
    pool.submit(task,url)

pool.shutdown(wait=True)

方法二：

#!/usr/bin/env python
# -*- coding:utf-8 -*- 
# Author: nulige
#进程

from concurrent.futures import ThreadPoolExecutor
import requests
import time

def task(url):
    response = requests.get(url)
    return response


def done(future,*args,**kwargs):
    response = future.result()
    print(response)

pool = ThreadPoolExecutor(6)

url_list = [
    'http://huaban.com/favorite/beauty/',
    'https://www.bing.com/',
    'https://www.baidu.com/',
    'https://www.sina.com/',
    'https://www.zhihu.com/',
    'https://www.tencent.com/',
]

for url in url_list:
    v = pool.submit(task,url)
    v.add_done_callback(done)

pool.shutdown(wait=True)

二、多进程

可以实现并发
但是，请求发送出去后和返回之前，中间时期进程空闲
编写方式：
    - 直接返回处理
    - 通过回调函数处理

方法一：

from concurrent.futures import ProcessPoolExecutor
import requests
import time

def task(url):
    response = requests.get(url)
    print(url,response)
    # 写正则表达式


pool = ProcessPoolExecutor(7)
url_list = [
    'http://www.cnblogs.com/wupeiqi',
    'http://huaban.com/favorite/beauty/',
    'http://www.bing.com',
    'http://www.zhihu.com',
    'http://www.sina.com',
    'http://www.baidu.com',
    'http://www.autohome.com.cn',
]
for url in url_list:
    pool.submit(task,url)

pool.shutdown(wait=True)

方法二：

from concurrent.futures import ProcessPoolExecutor
import requests
import time

def task(url):
    response = requests.get(url)
    return response

def done(future,*args,**kwargs):
    response = future.result()
    print(response.status_code,response.content)

pool = ProcessPoolExecutor(7)
url_list = [
    'http://www.cnblogs.com/wupeiqi',
    'http://huaban.com/favorite/beauty/',
    'http://www.bing.com',
    'http://www.zhihu.com',
    'http://www.sina.com',
    'http://www.baidu.com',
    'http://www.autohome.com.cn',
]
for url in url_list:
    v = pool.submit(task,url)
    v.add_done_callback(done)

pool.shutdown(wait=True

三、协程（微线程）+异步IO = 1个线程发送N个Http请求

异步IO （asyncio IO)

1、单线程，实现伪并发，同时处理两个任务，所有请求同时发出去，有返回值就继续执行。

#!/usr/bin/env python
# -*- coding:utf-8 -*- 
#Author: nulige

import asyncio

@asyncio.coroutine
def task():
    print('before...task......')
    yield from asyncio.sleep(5) # 发送Http请求，支持TCP获取结果..
    print('end...task......')

tasks = [task(), task()]

loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.gather(*tasks))
loop.close()

执行结果：

before...task......
before...task......
end...task......
end...task......

2、单线程，发送http请求原理(asyncio 内部完成了，异步IO操作)

asyncio：内部其实就是自己封装了http数据包

安装模块:

pip3 install asyncio

代码：

#!/usr/bin/env python
# -*- coding:utf-8 -*- 
#Author: nulige

import asyncio

@asyncio.coroutine
def task(host, url='/'):
    print('start', host, url)
    reader, writer = yield from asyncio.open_connection(host, 80)  #创建连接

    request_header_content = "GET %s HTTP/1.0
Host: %s

" % (url, host,)  #http请求格式
    request_header_content = bytes(request_header_content, encoding='utf-8')

    writer.write(request_header_content)
    yield from writer.drain()
    text = yield from reader.read()
    #返回结果
    print('end', host, url, text)
    writer.close()

#两个任务
tasks = [
    task('www.cnblogs.com', '/wupeiqi/'),
    task('dig.chouti.com', '/pic/show?nid=4073644713430508&lid=10273091')
]

loop = asyncio.get_event_loop()
results = loop.run_until_complete(asyncio.gather(*tasks))
loop.close()

3、asyncio(异步IO)+aiohttp(内部封装Http数据包)

安装模块：

pip3 install aiohttp

代码：

#!/usr/bin/env python
# -*- coding:utf-8 -*- 
#Author: nulige

import aiohttp
import asyncio

@asyncio.coroutine
def fetch_async(url):
    print(url)
    response = yield from aiohttp.request('GET', url)
    print(url, response)
    response.close()

tasks = [fetch_async('http://www.baidu.com/'), fetch_async('http://www.chouti.com/')]

event_loop = asyncio.get_event_loop()
results = event_loop.run_until_complete(asyncio.gather(*tasks))
event_loop.close()

4、asyncio+requests模块

安装模块

pip3 install requests

代码：

#!/usr/bin/env python
# -*- coding:utf-8 -*-
#Author: nulige

import asyncio
import requests


@asyncio.coroutine
def task(func, *args):
    print(func,args)
    loop = asyncio.get_event_loop()
    future = loop.run_in_executor(None, func, *args) # requests.get('http://www.cnblogs.com/wupeiqi/')
    response = yield from future
    print(response.url, response.content)


tasks = [
    task(requests.get, 'http://www.cnblogs.com/wupeiqi/'),
    task(requests.get, 'http://dig.chouti.com/pic/show?nid=4073644713430508&lid=10273091')
]

loop = asyncio.get_event_loop()
results = loop.run_until_complete(asyncio.gather(*tasks))
loop.close()

四、gevent,依赖greenlet(是个协程的模块)+异步ＩＯ(requests模块)

协程是微线程，规定这个线程先执行点什么，再执行点什么。

安装模块：

pip3 install greenlet

pip3 install gevent

代码：

#!/usr/bin/env python
# -*- coding:utf-8 -*- 
#Author: nulige

import gevent
import requests
from gevent import monkey
monkey.patch_all()   #找到你内部封装的异步ＩＯ的socket


def task(method, url, req_kwargs):
    #第一个任务来先传到这里
    print(method, url, req_kwargs)
    #request(get内部就是调用了request)
    response = requests.request(method=method, url=url, **req_kwargs)
    print(response.url, response.content)

##### 发送请求 #####
# gevent.joinall([
#     gevent.spawn(task, method='get', url='https://www.python.org/', req_kwargs={}),
#     gevent.spawn(task, method='get', url='https://www.yahoo.com/', req_kwargs={}),
#     gevent.spawn(task, method='get', url='https://github.com/', req_kwargs={}),
# ])

##### 发送请求（协程池控制最大协程数量，就是控制往远程发送多少个请求） #####
from gevent.pool import Pool
pool = Pool(5)
gevent.joinall([
    pool.spawn(task, method='get', url='https://www.python.org/', req_kwargs={}),
    pool.spawn(task, method='get', url='https://www.yahoo.com/', req_kwargs={}),
    pool.spawn(task, method='get', url='https://www.github.com/', req_kwargs={}),
])

执行结果：

get https://www.python.org/ {}
get https://www.yahoo.com/ {}
get https://www.github.com/ {}
后面省略......

五、 grequests模块 =  gevent+requests

安装模块：

pip3 install grequests

代码：

#!/usr/bin/env python
# -*- coding:utf-8 -*- 
#Author: nulige

import grequests

request_list = [
    grequests.get('http://httpbin.org/delay/1', timeout=0.001),
    grequests.get('http://fakedomain/'),
    grequests.get('http://httpbin.org/status/500')
]

#执行并获取响应列表
request_list = grequests.map(request_list)
print(request_list)

执行结果：

[None, None, <Response [500]>]

六、Twisted (用一个线程，发多个请求)

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from twisted.internet import defer
from twisted.web.client import getPage
from twisted.internet import reactor

def one_done(arg):
    print(arg)

def all_done(arg):
    print('done')
    reactor.stop()

@defer.inlineCallbacks
def task(url):
    res = getPage(bytes(url, encoding='utf8')) # 发送Http请求
    res.addCallback(one_done)
    yield res

url_list = [
    'http://www.cnblogs.com',
    'http://www.cnblogs.com',
    'http://www.cnblogs.com',
    'http://www.cnblogs.com',
]

defer_list = [] # [特殊，特殊，特殊(已经向url发送请求)]
for url in url_list:
    v = task(url)
    defer_list.append(v)

d = defer.DeferredList(defer_list)
d.addBoth(all_done)


reactor.run() # 死循环

七、Tornado (用一个线程，发多个请求)

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from tornado.httpclient import AsyncHTTPClient
from tornado.httpclient import HTTPRequest
from tornado import ioloop

COUNT = 0
def handle_response(response):
    global COUNT
    COUNT -= 1
    if response.error:
        print("Error:", response.error)
    else:
        print(response.body)
        # 方法同twisted
        # ioloop.IOLoop.current().stop()
    if COUNT == 0:
        ioloop.IOLoop.current().stop()

def func():
    url_list = [
        'http://www.baidu.com',
        'http://www.bing.com',
    ]
    global COUNT
    COUNT = len(url_list)
    for url in url_list:
        print(url)
        http_client = AsyncHTTPClient()
        http_client.fetch(HTTPRequest(url), handle_response)


ioloop.IOLoop.current().add_callback(func)
ioloop.IOLoop.current().start() # 死循环

执行结果：

http://www.baidu.com
http://www.bing.com

八、自定义异步IO框架

import socket
import select

# ########################## HTTP请求本质，阻塞 ##########################
"""
sk = socket.socket()
# 1.连接
sk.connect(('www.baidu.com',80,)) # IO阻塞
print('连接成功了...')

# 2. 连接成功发送消息
sk.send(b'GET / HTTP/1.0
Host:www.baidu.com

')
# sk.send(b'POST / HTTP/1.0
Host:www.baidu.com

k1=v1&k2=v2')

# 3. 等待着服务端响应
data = sk.recv(8096) # IO阻塞
print(data)

# 关闭连接
sk.close()
"""
# ########################## HTTP请求本质，非阻塞 ##########################
"""
sk = socket.socket()
sk.setblocking(False)
# 1.连接
try:
    sk.connect(('www.baidu.com',80,)) # IO阻塞
    print('连接成功了...')
except BlockingIOError as e:
    print(e)
# 2. 连接成功发送消息
sk.send(b'GET / HTTP/1.0
Host:www.baidu.com

')
# sk.send(b'POST / HTTP/1.0
Host:www.baidu.com

k1=v1&k2=v2')

# 3. 等待着服务端响应
data = sk.recv(8096) # IO阻塞
print(data)

# 关闭连接
sk.close()
"""

############################异步IO非阻塞################################
IO：就是读和写


class HttpRequest:
    def __init__(self,sk,host,callback):
        self.socket = sk
        self.host = host
        self.callback = callback
    def fileno(self):
        return self.socket.fileno()

class HttpResponse:
    def __init__(self,recv_data):
        self.recv_data = recv_data
        self.header_dict = {}
        self.body = None

        self.initialize()
    def initialize(self):
        headers, body = self.recv_data.split(b'

', 1)
        self.body = body
        header_list = headers.split(b'
')
        for h in header_list:
            h_str = str(h,encoding='utf-8')
            v = h_str.split(':',1)
            if len(v) == 2:
                self.header_dict[v[0]] = v[1]


class AsyncRequest:
    def __init__(self):
        self.conn = []
        self.connection = [] # 用于检测是否已经连接成功

    def add_request(self,host,callback):
        try:
            sk = socket.socket()
            sk.setblocking(0)
            sk.connect((host,80,))
        except BlockingIOError as e:
            pass
        request = HttpRequest(sk,host,callback)
        self.conn.append(request)
        self.connection.append(request)

    def run(self):

        while True:
            rlist,wlist,elist = select.select(self.conn,self.connection,self.conn,0.05)
            for w in wlist:
                print(w.host,'连接成功...')
                # 只要能循环到，表示socket和服务器端已经连接成功
                tpl = "GET / HTTP/1.0
Host:%s

"  %(w.host,)
                w.socket.send(bytes(tpl,encoding='utf-8'))
                self.connection.remove(w)
            for r in rlist:
                # r,是HttpRequest
                recv_data = bytes()
                while True:
                    try:
                        chunck = r.socket.recv(8096)  #最多接收的大小
                        recv_data += chunck
                    except Exception as e:
                        break
                response = HttpResponse(recv_data)
                r.callback(response)
                r.socket.close()
                self.conn.remove(r)
            if len(self.conn) == 0:
                break

def f1(response):
    print('保存到文件',response.header_dict)

def f2(response):
    print('保存到数据库', response.header_dict)

url_list = [
    {'host':'www.baidu.com','callback': f1},
    {'host':'cn.bing.com','callback': f2},
    {'host':'www.cnblogs.com','callback': f2},
]

req = AsyncRequest()
for item in url_list:
    req.add_request(item['host'],item['callback'])

req.run() 

备注：本篇博客用到的模块（python3.x）

#安装安装地址如下：

pip3 install aiohttp -i http://pypi.douban.com/simple --trusted-host pypi.douban.com 

pip3 install greenlet -i http://pypi.douban.com/simple --trusted-host pypi.douban.com 
 
pip3 install gevent -i http://pypi.douban.com/simple --trusted-host pypi.douban.com 

pip3 install grequests -i http://pypi.douban.com/simple --trusted-host pypi.douban.com 

pip3 install tornado -i http://pypi.douban.com/simple --trusted-host pypi.douban.com