How can I use scrapy middlewares to call a mail function?

Question

I have 15 spiders and every spider has its own content to send mail. My spiders also have their own spider_closed method which starts the mail sender but all of them same. At some point, the spider count will be 100 and I don't want to use the same functions again and again. Because of that, I try to use middlewares. I have been trying to use the spider_closed method in middlewares but it doesn't work.

middlewares.py

class FirstBotSpiderMiddleware:

    def __init__(self, spider):
        self.spider = spider
    
    @classmethod
    def from_crawler(cls, crawler):
        print("crawler works")
        crawler.signals.connect(crawler.spider.spider_closed, signal=signals.spider_opened)
        return cls(crawler)

    def spider_opened(self, spider):
        spider.logger.info('Spider opened: %s' % spider.name)
    
    def spider_closed(self, spider,reason):
        print("Spider closed works")
        if reason == "finished":
            content = spider.name + " works.\n"
        elif reason == "SD":
            content = spider.name + "works but same.\n"
        else:
            content = spider.name + " error"
        
        self.mailSender(spider,content)


    def mailSender(self,location,content):
        print("mailSender works")
        mailer = MailSender()
        mailer = MailSender.from_settings(settings)
        mailer.send(to=["Some Mail"], subject=content, body="Some body")

settings

# Scrapy settings for first_bot 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
import os
import sys



sys.path.append(os.path.dirname(os.path.abspath('.')))

BOT_NAME = 'first_bot'

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

# Crawl responsibly by identifying yourself (and your website) on the user-agent
USER_AGENT = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/22.0.1207.1 Safari/537.1"


# Obey robots.txt rules
ROBOTSTXT_OBEY = True

# Configure maximum concurrent requests performed by Scrapy (default: 16)
CONCURRENT_REQUESTS = 2

# 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 = 3
# 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 = {
    'first_bot.middlewares.FirstBotSpiderMiddleware': 543,
}

# Enable or disable downloader middlewares
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {
#    'first_bot.middlewares.FirstBotDownloaderMiddleware': 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 = {
#    'first_bot.pipelines.FirstBotPipeline': 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'

I am not getting any error or any mail. I also add some print and there is no output.

How can I run middlewares with my spiders? What is your suggestions?

Answer 1

It is important to run spider from scrapy crawl command so it will see whole project configuration correctly. Also, you need to make sure that custom middleware is listed in SPIDER_MIDDLEWARES dict and assigned order number. Main entry point for middleware is from_crawler method, which should receive crawler instance. Then you can write your middleware processing logic here by following rules mentioned here.