# Source code for scrapy.extensions.memusage

    """
    MemoryUsage extension

    See documentation in docs/topics/extensions.rst
    """
    import sys
    import socket
    import logging
    from pprint import pformat
    from importlib import import_module

    from twisted.internet import task

    from scrapy import signals
    from scrapy.exceptions import NotConfigured
    from scrapy.mail import MailSender
    from scrapy.utils.engine import get_engine_status

    logger = logging.getLogger(__name__)

    class MemoryUsage:

        def __init__(self, crawler):
            if not crawler.settings.getbool('MEMUSAGE_ENABLED'):
                raise NotConfigured
            try:
                # stdlib's resource module is only available on unix platforms.
                self.resource = import_module('resource')
            except ImportError:
                raise NotConfigured

            self.crawler = crawler
            self.warned = False
            self.notify_mails = crawler.settings.getlist('MEMUSAGE_NOTIFY_MAIL')
            self.limit = crawler.settings.getint('MEMUSAGE_LIMIT_MB')*1024*1024
            self.warning = crawler.settings.getint('MEMUSAGE_WARNING_MB')*1024*1024
            self.check_interval = crawler.settings.getfloat('MEMUSAGE_CHECK_INTERVAL_SECONDS')
            self.mail = MailSender.from_settings(crawler.settings)
            crawler.signals.connect(self.engine_started, signal=signals.engine_started)
            crawler.signals.connect(self.engine_stopped, signal=signals.engine_stopped)

        @classmethod
        def from_crawler(cls, crawler):
            return cls(crawler)

        def get_virtual_size(self):
            size = self.resource.getrusage(self.resource.RUSAGE_SELF).ru_maxrss
            if sys.platform != 'darwin':
                # on macOS ru_maxrss is in bytes, on Linux it is in KB
                size *= 1024
            return size

        def engine_started(self):
            self.crawler.stats.set_value('memusage/startup', self.get_virtual_size())
            self.tasks = []
            tsk = task.LoopingCall(self.update)
            self.tasks.append(tsk)
            tsk.start(self.check_interval, now=True)
            if self.limit:
                tsk = task.LoopingCall(self._check_limit)
                self.tasks.append(tsk)
                tsk.start(self.check_interval, now=True)
            if self.warning:
                tsk = task.LoopingCall(self._check_warning)
                self.tasks.append(tsk)
                tsk.start(self.check_interval, now=True)

        def engine_stopped(self):
            for tsk in self.tasks:
                if tsk.running:
                    tsk.stop()

        def update(self):
            self.crawler.stats.max_value('memusage/max', self.get_virtual_size())

        def _check_limit(self):
            if self.get_virtual_size() > self.limit:
                self.crawler.stats.set_value('memusage/limit_reached', 1)
                mem = self.limit/1024/1024
                logger.error("Memory usage exceeded %(memusage)dM. Shutting down Scrapy...",
                             {'memusage': mem}, extra={'crawler': self.crawler})
                if self.notify_mails:
                    subj = (
                        f"{self.crawler.settings['BOT_NAME']} terminated: "
                        f"memory usage exceeded {mem}M at {socket.gethostname()}"
                    )
                    self._send_report(self.notify_mails, subj)
                    self.crawler.stats.set_value('memusage/limit_notified', 1)

                open_spiders = self.crawler.engine.open_spiders
                if open_spiders:
                    for spider in open_spiders:
                        self.crawler.engine.close_spider(spider, 'memusage_exceeded')
                else:
                    self.crawler.stop()

        def _check_warning(self):
            if self.warned: # warn only once
                return
            if self.get_virtual_size() > self.warning:
                self.crawler.stats.set_value('memusage/warning_reached', 1)
                mem = self.warning/1024/1024
                logger.warning("Memory usage reached %(memusage)dM",
                               {'memusage': mem}, extra={'crawler': self.crawler})
                if self.notify_mails:
                    subj = (
                        f"{self.crawler.settings['BOT_NAME']} warning: "
                        f"memory usage reached {mem}M at {socket.gethostname()}"
                    )
                    self._send_report(self.notify_mails, subj)
                    self.crawler.stats.set_value('memusage/warning_notified', 1)
                self.warned = True

        def _send_report(self, rcpts, subject):
            """send notification mail with some additional useful info"""
            stats = self.crawler.stats
            s = f"Memory usage at engine startup : {stats.get_value('memusage/startup')/1024/1024}M\r\n"
            s += f"Maximum memory usage          : {stats.get_value('memusage/max')/1024/1024}M\r\n"
            s += f"Current memory usage          : {self.get_virtual_size()/1024/1024}M\r\n"

            s += "ENGINE STATUS ------------------------------------------------------- \r\n"
            s += "\r\n"
            s += pformat(get_engine_status(self.crawler.engine))
            s += "\r\n"
            self.mail.send(rcpts, subject, s)