ADD file via upload

Scrapy-Redis-Zhihu/scrapy_redis/scheduler.py

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+import importlib
+import six
+
+from scrapy.utils.misc import load_object
+
+from . import connection, defaults
+
+
+# TODO: add SCRAPY_JOB support.
+class Scheduler(object):
+    """Redis-based scheduler
+
+    Settings
+    --------
+    SCHEDULER_PERSIST : bool (default: False)
+        Whether to persist or clear redis queue.
+    SCHEDULER_FLUSH_ON_START : bool (default: False)
+        Whether to flush redis queue on start.
+    SCHEDULER_IDLE_BEFORE_CLOSE : int (default: 0)
+        How many seconds to wait before closing if no message is received.
+    SCHEDULER_QUEUE_KEY : str
+        Scheduler redis key.
+    SCHEDULER_QUEUE_CLASS : str
+        Scheduler queue class.
+    SCHEDULER_DUPEFILTER_KEY : str
+        Scheduler dupefilter redis key.
+    SCHEDULER_DUPEFILTER_CLASS : str
+        Scheduler dupefilter class.
+    SCHEDULER_SERIALIZER : str
+        Scheduler serializer.
+
+    """
+
+    def __init__(self, server,
+                 persist=False,
+                 flush_on_start=False,
+                 queue_key=defaults.SCHEDULER_QUEUE_KEY,
+                 queue_cls=defaults.SCHEDULER_QUEUE_CLASS,
+                 dupefilter_key=defaults.SCHEDULER_DUPEFILTER_KEY,
+                 dupefilter_cls=defaults.SCHEDULER_DUPEFILTER_CLASS,
+                 idle_before_close=0,
+                 serializer=None):
+        """Initialize scheduler.
+
+        Parameters
+        ----------
+        server : Redis
+            The redis server instance.
+        persist : bool
+            Whether to flush requests when closing. Default is False.
+        flush_on_start : bool
+            Whether to flush requests on start. Default is False.
+        queue_key : str
+            Requests queue key.
+        queue_cls : str
+            Importable path to the queue class.
+        dupefilter_key : str
+            Duplicates filter key.
+        dupefilter_cls : str
+            Importable path to the dupefilter class.
+        idle_before_close : int
+            Timeout before giving up.
+
+        """
+        if idle_before_close < 0:
+            raise TypeError("idle_before_close cannot be negative")
+
+        self.server = server
+        self.persist = persist
+        self.flush_on_start = flush_on_start
+        self.queue_key = queue_key
+        self.queue_cls = queue_cls
+        self.dupefilter_cls = dupefilter_cls
+        self.dupefilter_key = dupefilter_key
+        self.idle_before_close = idle_before_close
+        self.serializer = serializer
+        self.stats = None
+
+    def __len__(self):
+        return len(self.queue)
+
+    @classmethod
+    def from_settings(cls, settings):
+        kwargs = {
+            'persist': settings.getbool('SCHEDULER_PERSIST'),
+            'flush_on_start': settings.getbool('SCHEDULER_FLUSH_ON_START'),
+            'idle_before_close': settings.getint('SCHEDULER_IDLE_BEFORE_CLOSE'),
+        }
+
+        # If these values are missing, it means we want to use the defaults.
+        optional = {
+            # TODO: Use custom prefixes for this settings to note that are
+            # specific to scrapy-redis.
+            'queue_key': 'SCHEDULER_QUEUE_KEY',
+            'queue_cls': 'SCHEDULER_QUEUE_CLASS',
+            'dupefilter_key': 'SCHEDULER_DUPEFILTER_KEY',
+            # We use the default setting name to keep compatibility.
+            'dupefilter_cls': 'DUPEFILTER_CLASS',
+            'serializer': 'SCHEDULER_SERIALIZER',
+        }
+        for name, setting_name in optional.items():
+            val = settings.get(setting_name)
+            if val:
+                kwargs[name] = val
+
+        # Support serializer as a path to a module.
+        if isinstance(kwargs.get('serializer'), six.string_types):
+            kwargs['serializer'] = importlib.import_module(kwargs['serializer'])
+
+        server = connection.from_settings(settings)
+        # Ensure the connection is working.
+        server.ping()
+
+        return cls(server=server, **kwargs)
+
+    @classmethod
+    def from_crawler(cls, crawler):
+        instance = cls.from_settings(crawler.settings)
+        # FIXME: for now, stats are only supported from this constructor
+        instance.stats = crawler.stats
+        return instance
+
+    def open(self, spider):
+        self.spider = spider
+
+        try:
+            self.queue = load_object(self.queue_cls)(
+                server=self.server,
+                spider=spider,
+                key=self.queue_key % {'spider': spider.name},
+                serializer=self.serializer,
+            )
+        except TypeError as e:
+            raise ValueError("Failed to instantiate queue class '%s': %s",
+                             self.queue_cls, e)
+
+        self.df = load_object(self.dupefilter_cls).from_spider(spider)
+
+        if self.flush_on_start:
+            self.flush()
+        # notice if there are requests already in the queue to resume the crawl
+        if len(self.queue):
+            spider.log("Resuming crawl (%d requests scheduled)" % len(self.queue))
+
+    def close(self, reason):
+        if not self.persist:
+            self.flush()
+
+    def flush(self):
+        self.df.clear()
+        self.queue.clear()
+
+    def enqueue_request(self, request):
+        if not request.dont_filter and self.df.request_seen(request):
+            self.df.log(request, self.spider)
+            return False
+        if self.stats:
+            self.stats.inc_value('scheduler/enqueued/redis', spider=self.spider)
+        self.queue.push(request)
+        return True
+
+    def next_request(self):
+        block_pop_timeout = self.idle_before_close
+        request = self.queue.pop(block_pop_timeout)
+        if request and self.stats:
+            self.stats.inc_value('scheduler/dequeued/redis', spider=self.spider)
+        return request
+
+    def has_pending_requests(self):
+        return len(self) > 0