【Python爬虫实战】scrapy爬取某资讯网站并存入MySQL

本次爬取目标网站为 https://www.nanjixiong.com/forum-2-1.html
任务是爬取列表页+详情页数据

在爬取过程中发现几点问题：

1. 每次运行scrapy爬取内容的顺序都不一致。
   原因：百度原因是scrapy是一个异步处理框架，也就是说Scrapy发送请求之后，不会等待这个请求的响应（也就是不会阻塞），而是可以同时发送其他请求或者做别的事情。而我们知道服务器对于请求的响应是由很多方面的因素影响的，如猫之良品所说的网络速度、解析速度、资源抢占等等，其响应的顺序是难以预测的。
2. 在使用普通的同步写入方法时，发现部分数据最后写不到数据库中。
   原因：百度原因是同步异步（但我还不是很理解这个地方，如有大佬朋友清楚原因，请指教下本小白，感谢！！）。①同步： 同步写入数据速度比较慢， 而爬虫速度比较快，普通的mysql操作是同步操作，插入数据的速度（即I/O读写）远远低于spider中解析数据的速度。 可能导致数据最后写不到数据库中。②异步： 是将爬虫的数据先放到一个连接池中， 再同时将连接池的数据写入到数据库中， 这样既可以提高数据库的写入速度， 同时也可以将爬取到的所有数据都写到数据库中， 保证数据的完整性。

使用实现代码如下：
分别测试了延迟与正常状态下的同步写入和异步写入，效果如下
spider部分

import scrapy
import re
from copy import deepcopy
from up3Dprint.items import Up3DprintItem


class NanjixiongSpider(scrapy.Spider):
    name = 'nanjixiong'
    allowed_domains = ['nanjixiong.com']
    start_urls = ['https://www.nanjixiong.com/forum-2-1.html']

    def parse(self, response, **kwargs):
        new_list = response.xpath('//*[@id="threadlisttableid"]/tbody')
        for new in new_list:
            item = Up3DprintItem()
            item['id'] = new.xpath('./@id').extract_first()
            item['title'] = new.xpath('./tr/th/div[1]/a[2]/text()').extract_first()
            item['href'] = new.xpath('./tr/th/div[1]/a[2]/@href').extract_first()
            yield scrapy.Request(
                url='https://www.nanjixiong.com/' + item['href'],
                callback=self.parse_detail,
                meta={
     'item':deepcopy(item)}
            )

    def parse_detail(self, resopnse):
        item = resopnse.meta['item']
        item['publish_year'] = resopnse.xpath('//*[@id="wp"]/div[2]/div[2]/div[1]/div/div[1]/b/text()').extract_first()
        item['publish_month'] = resopnse.xpath('//*[@id="wp"]/div[2]/div[2]/div[1]/div/div[2]/text()').extract_first()
        item['publish_date'] = resopnse.xpath('//*[@id="wp"]/div[2]/div[2]/div[1]/div/div[3]/text()').extract_first()
        item['image'] = resopnse.xpath('//*[@id="ct"]//td[@class="t_f"]//ignore_js_op//img/@zoomfile').extract()
        content = resopnse.xpath('//*[@id="ct"]//td[@class="t_f"]/text() | '
                                 '//*[@id="ct"]//td[@class="t_f"]/strong//text() | '
                                 '//*[@id="ct"]//td[@class="t_f"]/font//text() | '
                                 '//*[@id="ct"]//td[@class="t_f"]/ul//text()').extract()
        content = [i for i in content if re.match(r'[\r\n]+$', i) is None]
        item['content'] = ''.join([b + '\n' if b.endswith(('。', '！', '；', '？')) else b for b in content])
        if item['image'] is not None:
            item['image'] = ['https://www.nanjixiong.com/' + image for image in item['image']]
        yield item

item部分：

import scrapy


class Up3DprintItem(scrapy.Item):
    id = scrapy.Field()
    title = scrapy.Field()
    href = scrapy.Field()
    publish_year = scrapy.Field()
    publish_month = scrapy.Field()
    publish_date = scrapy.Field()
    image = scrapy.Field()
    content = scrapy.Field()

middlewares部分：

import random


class RandomUserAgentMiddleware:
    def process_request(self,request,spider):
        ua = random.choice(spider.settings.get('USER_AGENT_LIST'))
        request.headers['User-Agent'] = ua

settings部分：

# Scrapy settings for up3Dprint project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
#     https://docs.scrapy.org/en/latest/topics/settings.html
#     https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#     https://docs.scrapy.org/en/latest/topics/spider-middleware.html

BOT_NAME = 'up3Dprint'

SPIDER_MODULES = ['up3Dprint.spiders']
NEWSPIDER_MODULE = 'up3Dprint.spiders'

LOG_LEVEL = 'ERROR'

# Crawl responsibly by identifying yourself (and your website) on the user-agent
USER_AGENT_LIST = ['Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.141 Safari/537.36',
                   'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.141 Safari/537.36 Edg/87.0.664.75',
                   'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:72.0) Gecko/20100101 Firefox/72.0',
                   'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.71 Safari/537.36',
                   'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.64 Safari/537.11',
                   'Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.16 (KHTML, like Gecko) Chrome/10.0.648.133 Safari/534.16',
                   'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_0) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11',
                   'Mozilla/5.0 (Windows NT 6.1; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0',
                   'Mozilla/5.0 (X11; U; Linux x86_64; zh-CN; rv:1.9.2.10) Gecko/20100922 Ubuntu/10.10 (maverick) Firefox/3.6.10',
                   'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv,2.0.1) Gecko/20100101 Firefox/4.0.1',
                   'Mozilla/5.0 (Windows NT 6.1; rv,2.0.1) Gecko/20100101 Firefox/4.0.1',
                   'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/534.57.2 (KHTML, like Gecko) Version/5.1.7 Safari/534.57.2',
                   'Mozilla/5.0 (Windows; U; Windows NT 6.1; en-us) AppleWebKit/534.50 (KHTML, like Gecko) Version/5.1 Safari/534.50',
                   'Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_3 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8J2 Safari/6533.18.5',
                   'Mozilla/5.0 (iPad; U; CPU OS 4_3_3 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8J2 Safari/6533.18.5',
                   'Opera/9.80 (Macintosh; Intel Mac OS X 10.6.8; U; en) Presto/2.8.131 Version/11.11',
                   'Opera/9.80 (Windows NT 6.1; U; en) Presto/2.8.131 Version/11.11',
                   'Opera/9.80 (Android 2.3.4; Linux; Opera Mobi/build-1107180945; U; en-GB) Presto/2.8.149 Version/11.10',
                   'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.95 Safari/537.36 OPR/26.0.1656.60',
                   'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.81 Safari/537.36 SE 2.X MetaSr 1.0',
                   'Mozilla/5.0 (Windows NT 5.1) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.84 Safari/535.11 SE 2.X MetaSr 1.0',
                   'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.122 UBrowser/4.0.3214.0 Safari/537.36',
                   'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 UBrowser/6.2.4094.1 Safari/537.36']

# Obey robots.txt rules
ROBOTSTXT_OBEY = False

MYSQL_HOST = '***'
MYSQL_USER = '***'
MYSQL_PASSWORD = '***'
MYSQL_DB_NAME = '***'
MYSQL_PORT = 3306
MYSQL_CHARSET = 'utf8'

# Configure maximum concurrent requests performed by Scrapy (default: 16)
#CONCURRENT_REQUESTS = 32

# Configure a delay for requests for the same website (default: 0)
# See https://docs.scrapy.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
DOWNLOAD_DELAY = 1
# The download delay setting will honor only one of:
#CONCURRENT_REQUESTS_PER_DOMAIN = 16
#CONCURRENT_REQUESTS_PER_IP = 16

# Disable cookies (enabled by default)
#COOKIES_ENABLED = False

# Disable Telnet Console (enabled by default)
#TELNETCONSOLE_ENABLED = False

# Override the default request headers:
#DEFAULT_REQUEST_HEADERS = {
     
#   'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
#   'Accept-Language': 'en',
#}

# Enable or disable spider middlewares
# See https://docs.scrapy.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
     
#    'up3Dprint.middlewares.Up3DprintSpiderMiddleware': 543,
#}

# Enable or disable downloader middlewares
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
DOWNLOADER_MIDDLEWARES = {
     
   'up3Dprint.middlewares.RandomUserAgentMiddleware': 543,
}

# Enable or disable extensions
# See https://docs.scrapy.org/en/latest/topics/extensions.html
#EXTENSIONS = {
     
#    'scrapy.extensions.telnet.TelnetConsole': None,
#}

# Configure item pipelines
# See https://docs.scrapy.org/en/latest/topics/item-pipeline.html
ITEM_PIPELINES = {
     
   'up3Dprint.pipelines.Up3DprintPipeline': 300,
}

# Enable and configure the AutoThrottle extension (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/autothrottle.html
#AUTOTHROTTLE_ENABLED = True
# The initial download delay
#AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
#AUTOTHROTTLE_MAX_DELAY = 60
# The average number of requests Scrapy should be sending in parallel to
# each remote server
#AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
# Enable showing throttling stats for every response received:
#AUTOTHROTTLE_DEBUG = False

# Enable and configure HTTP caching (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
#HTTPCACHE_ENABLED = True
#HTTPCACHE_EXPIRATION_SECS = 0
#HTTPCACHE_DIR = 'httpcache'
#HTTPCACHE_IGNORE_HTTP_CODES = []
#HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'

同步写入的pipelines部分:

import pymysql
from up3Dprint.settings import MYSQL_HOST,MYSQL_USER,MYSQL_PASSWORD,MYSQL_DB_NAME,MYSQL_PORT,MYSQL_CHARSET


class Up3DprintPipeline:
    conn = None
    cursor = None
    def open_spider(self, spider):
        self.conn = pymysql.connect(host=MYSQL_HOST,user=MYSQL_USER,passwd=MYSQL_PASSWORD,db=MYSQL_DB_NAME,port=MYSQL_PORT,charset=MYSQL_CHARSET)
        self.cursor = self.conn.cursor()

    def process_item(self, item, spider):
        try:
            sql = 'insert into 3dprint_nanjixiong(id,title,href,publish_year,publish_month,publish_date,image,content) values(%s,%s,%s,%s,%s,%s,%s,%s)'
            data = [item['id'],item['title'],item['href'],item['publish_year'],item['publish_month'],item['publish_date'],str(item['image']),item['content']]
            self.cursor.execute(sql,data)
            self.conn.commit()
            print(f'{item["id"]} 插入成功！')
        except Exception as e:
            print('插入数据失败', e)
            self.conn.rollback()
        return item

    def close_spider(self, spider):
        self.cursor.close()
        self.conn.close()

同步写入时，分别测试了无延迟和延迟1秒的情况，但都有部分数据无法写入数据库。
类似这样：部分详情页数据为null

异步写入的pipelines部分:

import pymysql
from twisted.enterprise import adbapi


class Up3DprintPipeline(object):
    # 初始化函数
    def __init__(self, db_pool):
        self.db_pool = db_pool

    # 从settings配置文件中读取数据库连接参数
    @classmethod
    def from_settings(cls, settings):
        # db_params接收连接数据库的参数
        db_params = dict(
            host=settings['MYSQL_HOST'],
            user=settings['MYSQL_USER'],
            password=settings['MYSQL_PASSWORD'],
            port=settings['MYSQL_PORT'],
            database=settings['MYSQL_DB_NAME'],
            charset=settings['MYSQL_CHARSET'],
            # 设置游标类型
            cursorclass=pymysql.cursors.DictCursor
        )
        # 创建一个数据库连接池对象，这个连接池可以包含多个connect连接对象
        # 参数1：操作数据库的包名
        # 参数2：连接数据库的参数
        db_pool = adbapi.ConnectionPool('pymysql', **db_params)
        # 返回一个pipeline对象
        return cls(db_pool)

    # 使用twisted将mysql插入变为异步执行
    def process_item(self, item, spider):
        # 把要执行的sql放入连接池
        # 参数1：在线程中被执行的sql语句
        # 参数2：要保存的数据
        result = self.db_pool.runInteraction(self.insert, item)
        # 给result绑定一个回调函数，用于监听错误信息.如果sql执行发送错误,自动回调addErrBack()函数
        result.addErrback(self.handle_error, item, spider)
        # 返回Item
        return item

    # sql函数执行具体的插入操作
    def insert(self, cursor, item):
        sql = 'insert into 3dprint_nanjixiong(id,title,href,publish_year,publish_month,publish_date,image,content) values(%s,%s,%s,%s,%s,%s,%s,%s)'
        data = [item['id'],item['title'],item['href'],item['publish_year'],item['publish_month'],item['publish_date'],str(item['image']),item['content']]
        cursor.execute(sql, data)
        print(f'{item["id"]} 插入成功！')

    # 错误函数
    def handle_error(self, failure, item, spider):
        # 输出错误信息
        print(failure)

异步写入时，分别测试了无延迟和延迟1秒的情况，结果延迟1秒时候数据成功写入数据库，无延迟时还是存在部分数据无法写入。

*************后面又尝试多几次，发现好像不管是否延迟，都会存在有部分数据无法写入的情况。。而且无法写入的数据好像都是随机的。这是为什么呢。。。