forked from scrapy/scrapy
-
Notifications
You must be signed in to change notification settings - Fork 0
/
engine.py
346 lines (284 loc) · 12.8 KB
/
engine.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
"""
This is the Scrapy engine which controls the Scheduler, Downloader and Spiders.
For more information see docs/topics/architecture.rst
"""
import logging
from time import time
from twisted.internet import defer, task
from twisted.python.failure import Failure
from scrapy import signals
from scrapy.core.scraper import Scraper
from scrapy.exceptions import DontCloseSpider
from scrapy.http import Response, Request
from scrapy.utils.misc import load_object
from scrapy.utils.reactor import CallLaterOnce
from scrapy.utils.log import logformatter_adapter, failure_to_exc_info
logger = logging.getLogger(__name__)
class Slot(object):
def __init__(self, start_requests, close_if_idle, nextcall, scheduler):
self.closing = False
self.inprogress = set() # requests in progress
self.start_requests = iter(start_requests)
self.close_if_idle = close_if_idle
self.nextcall = nextcall
self.scheduler = scheduler
self.heartbeat = task.LoopingCall(nextcall.schedule)
def add_request(self, request):
self.inprogress.add(request)
def remove_request(self, request):
self.inprogress.remove(request)
self._maybe_fire_closing()
def close(self):
self.closing = defer.Deferred()
self._maybe_fire_closing()
return self.closing
def _maybe_fire_closing(self):
if self.closing and not self.inprogress:
if self.nextcall:
self.nextcall.cancel()
if self.heartbeat.running:
self.heartbeat.stop()
self.closing.callback(None)
class ExecutionEngine(object):
def __init__(self, crawler, spider_closed_callback):
self.crawler = crawler
self.settings = crawler.settings
self.signals = crawler.signals
self.logformatter = crawler.logformatter
self.slot = None
self.spider = None
self.running = False
self.paused = False
self.scheduler_cls = load_object(self.settings['SCHEDULER'])
downloader_cls = load_object(self.settings['DOWNLOADER'])
self.downloader = downloader_cls(crawler)
self.scraper = Scraper(crawler)
self._spider_closed_callback = spider_closed_callback
@defer.inlineCallbacks
def start(self):
"""Start the execution engine"""
assert not self.running, "Engine already running"
self.start_time = time()
yield self.signals.send_catch_log_deferred(signal=signals.engine_started)
self.running = True
self._closewait = defer.Deferred()
yield self._closewait
def stop(self):
"""Stop the execution engine gracefully"""
assert self.running, "Engine not running"
self.running = False
dfd = self._close_all_spiders()
return dfd.addBoth(lambda _: self._finish_stopping_engine())
def close(self):
"""Close the execution engine gracefully.
If it has already been started, stop it. In all cases, close all spiders
and the downloader.
"""
if self.running:
# Will also close spiders and downloader
return self.stop()
elif self.open_spiders:
# Will also close downloader
return self._close_all_spiders()
else:
return defer.succeed(self.downloader.close())
def pause(self):
"""Pause the execution engine"""
self.paused = True
def unpause(self):
"""Resume the execution engine"""
self.paused = False
def _next_request(self, spider):
slot = self.slot
if not slot:
return
if self.paused:
return
while not self._needs_backout(spider):
if not self._next_request_from_scheduler(spider):
break
if slot.start_requests and not self._needs_backout(spider):
try:
request = next(slot.start_requests)
except StopIteration:
slot.start_requests = None
except Exception:
slot.start_requests = None
logger.error('Error while obtaining start requests',
exc_info=True, extra={'spider': spider})
else:
self.crawl(request, spider)
if self.spider_is_idle(spider) and slot.close_if_idle:
self._spider_idle(spider)
def _needs_backout(self, spider):
slot = self.slot
return not self.running \
or slot.closing \
or self.downloader.needs_backout() \
or self.scraper.slot.needs_backout()
def _next_request_from_scheduler(self, spider):
slot = self.slot
request = slot.scheduler.next_request()
if not request:
return
d = self._download(request, spider)
d.addBoth(self._handle_downloader_output, request, spider)
d.addErrback(lambda f: logger.info('Error while handling downloader output',
exc_info=failure_to_exc_info(f),
extra={'spider': spider}))
d.addBoth(lambda _: slot.remove_request(request))
d.addErrback(lambda f: logger.info('Error while removing request from slot',
exc_info=failure_to_exc_info(f),
extra={'spider': spider}))
d.addBoth(lambda _: slot.nextcall.schedule())
d.addErrback(lambda f: logger.info('Error while scheduling new request',
exc_info=failure_to_exc_info(f),
extra={'spider': spider}))
return d
def _handle_downloader_output(self, response, request, spider):
assert isinstance(response, (Request, Response, Failure)), response
# downloader middleware can return requests (for example, redirects)
if isinstance(response, Request):
self.crawl(response, spider)
return
# response is a Response or Failure
d = self.scraper.enqueue_scrape(response, request, spider)
d.addErrback(lambda f: logger.error('Error while enqueuing downloader output',
exc_info=failure_to_exc_info(f),
extra={'spider': spider}))
return d
def spider_is_idle(self, spider):
if not self.scraper.slot.is_idle():
# scraper is not idle
return False
if self.downloader.active:
# downloader has pending requests
return False
if self.slot.start_requests is not None:
# not all start requests are handled
return False
if self.slot.scheduler.has_pending_requests():
# scheduler has pending requests
return False
return True
@property
def open_spiders(self):
return [self.spider] if self.spider else []
def has_capacity(self):
"""Does the engine have capacity to handle more spiders"""
return not bool(self.slot)
def crawl(self, request, spider):
assert spider in self.open_spiders, \
"Spider %r not opened when crawling: %s" % (spider.name, request)
self.schedule(request, spider)
self.slot.nextcall.schedule()
def schedule(self, request, spider):
self.signals.send_catch_log(signal=signals.request_scheduled,
request=request, spider=spider)
if not self.slot.scheduler.enqueue_request(request):
self.signals.send_catch_log(signal=signals.request_dropped,
request=request, spider=spider)
def download(self, request, spider):
d = self._download(request, spider)
d.addBoth(self._downloaded, self.slot, request, spider)
return d
def _downloaded(self, response, slot, request, spider):
slot.remove_request(request)
return self.download(response, spider) \
if isinstance(response, Request) else response
def _download(self, request, spider):
slot = self.slot
slot.add_request(request)
def _on_success(response):
assert isinstance(response, (Response, Request))
if isinstance(response, Response):
response.request = request # tie request to response received
logkws = self.logformatter.crawled(request, response, spider)
logger.log(*logformatter_adapter(logkws), extra={'spider': spider})
self.signals.send_catch_log(signal=signals.response_received, \
response=response, request=request, spider=spider)
return response
def _on_complete(_):
slot.nextcall.schedule()
return _
dwld = self.downloader.fetch(request, spider)
dwld.addCallbacks(_on_success)
dwld.addBoth(_on_complete)
return dwld
@defer.inlineCallbacks
def open_spider(self, spider, start_requests=(), close_if_idle=True):
assert self.has_capacity(), "No free spider slot when opening %r" % \
spider.name
logger.info("Spider opened", extra={'spider': spider})
nextcall = CallLaterOnce(self._next_request, spider)
scheduler = self.scheduler_cls.from_crawler(self.crawler)
start_requests = yield self.scraper.spidermw.process_start_requests(start_requests, spider)
slot = Slot(start_requests, close_if_idle, nextcall, scheduler)
self.slot = slot
self.spider = spider
yield scheduler.open(spider)
yield self.scraper.open_spider(spider)
self.crawler.stats.open_spider(spider)
yield self.signals.send_catch_log_deferred(signals.spider_opened, spider=spider)
slot.nextcall.schedule()
slot.heartbeat.start(5)
def _spider_idle(self, spider):
"""Called when a spider gets idle. This function is called when there
are no remaining pages to download or schedule. It can be called
multiple times. If some extension raises a DontCloseSpider exception
(in the spider_idle signal handler) the spider is not closed until the
next loop and this function is guaranteed to be called (at least) once
again for this spider.
"""
res = self.signals.send_catch_log(signal=signals.spider_idle, \
spider=spider, dont_log=DontCloseSpider)
if any(isinstance(x, Failure) and isinstance(x.value, DontCloseSpider) \
for _, x in res):
return
if self.spider_is_idle(spider):
self.close_spider(spider, reason='finished')
def close_spider(self, spider, reason='cancelled'):
"""Close (cancel) spider and clear all its outstanding requests"""
slot = self.slot
if slot.closing:
return slot.closing
logger.info("Closing spider (%(reason)s)",
{'reason': reason},
extra={'spider': spider})
dfd = slot.close()
def log_failure(msg):
def errback(failure):
logger.error(
msg,
exc_info=failure_to_exc_info(failure),
extra={'spider': spider}
)
return errback
dfd.addBoth(lambda _: self.downloader.close())
dfd.addErrback(log_failure('Downloader close failure'))
dfd.addBoth(lambda _: self.scraper.close_spider(spider))
dfd.addErrback(log_failure('Scraper close failure'))
dfd.addBoth(lambda _: slot.scheduler.close(reason))
dfd.addErrback(log_failure('Scheduler close failure'))
dfd.addBoth(lambda _: self.signals.send_catch_log_deferred(
signal=signals.spider_closed, spider=spider, reason=reason))
dfd.addErrback(log_failure('Error while sending spider_close signal'))
dfd.addBoth(lambda _: self.crawler.stats.close_spider(spider, reason=reason))
dfd.addErrback(log_failure('Stats close failure'))
dfd.addBoth(lambda _: logger.info("Spider closed (%(reason)s)",
{'reason': reason},
extra={'spider': spider}))
dfd.addBoth(lambda _: setattr(self, 'slot', None))
dfd.addErrback(log_failure('Error while unassigning slot'))
dfd.addBoth(lambda _: setattr(self, 'spider', None))
dfd.addErrback(log_failure('Error while unassigning spider'))
dfd.addBoth(lambda _: self._spider_closed_callback(spider))
return dfd
def _close_all_spiders(self):
dfds = [self.close_spider(s, reason='shutdown') for s in self.open_spiders]
dlist = defer.DeferredList(dfds)
return dlist
@defer.inlineCallbacks
def _finish_stopping_engine(self):
yield self.signals.send_catch_log_deferred(signal=signals.engine_stopped)
self._closewait.callback(None)