Logging to specific error log file in scrapy

Question

I am running a log of scrapy by doing this:

from scrapy import log
class MySpider(BaseSpider):
  name = "myspider"  

  def __init__(self, name=None, **kwargs):
        LOG_FILE = "logs/spider.log"
        log.log.defaultObserver = log.log.DefaultObserver()
        log.log.defaultObserver.start()
        log.started = False
        log.start(LOG_FILE, loglevel=log.INFO)
        super(MySpider, self).__init__(name, **kwargs)

    def parse(self,response):
        ....
        raise Exception("Something went wrong!")
        log.msg('Something went wrong!', log.ERROR)

        # Somehow write to a separate error log here.

Then I run the spider like this:

scrapy crawl myspider

This would store all the log.INFO data as well as log.ERROR into spider.log.

If an error occurs, I would also like to store those details in a separate log file called spider_errors.log. It would make it easier to search for errors that occurred rather than trying to scan through the entire spider.log file (which could be huge).

Is there a way to do this?

EDIT:

Trying with PythonLoggingObserver:

def __init__(self, name=None, **kwargs):
        LOG_FILE = 'logs/spider.log'
        ERR_File = 'logs/spider_error.log'

        observer = log.log.PythonLoggingObserver()
        observer.start()

        log.started = False     
        log.start(LOG_FILE, loglevel=log.INFO)
        log.start(ERR_FILE, loglevel=log.ERROR)

But I get ERROR: No handlers could be found for logger "twisted"

Answer 1

Just let logging do the job. Try to use PythonLoggingObserver instead of DefaultObserver:

• configure two loggers (one for INFO and one for ERROR messages) directly in python, or via fileconfig, or via dictconfig (see docs)

• start it in spider's __init__:

  def __init__(self, name=None, **kwargs):
      # TODO: configure logging: e.g. logging.config.fileConfig("logging.conf")
      observer = log.PythonLoggingObserver()
      observer.start()
  

Let me know if you need help with configuring loggers.

EDIT:

Another option is to start two file log observers in __init__.py:

from scrapy.log import ScrapyFileLogObserver
from scrapy import log


class MySpider(BaseSpider):
    name = "myspider"  

    def __init__(self, name=None, **kwargs):
        ScrapyFileLogObserver(open("spider.log", 'w'), level=logging.INFO).start()
        ScrapyFileLogObserver(open("spider_error.log", 'w'), level=logging.ERROR).start()

        super(MySpider, self).__init__(name, **kwargs)

    ...