def _check_media_to_download(self, result, request, info):
if result is not None:
return result
# Download request and process its response
return mustbe_deferred(self.download, request, info).addCallbacks(
callback=self.media_downloaded, callbackArgs=(request, info),
errback=self.media_failed, errbackArgs=(request, info))
def _download(self, slot, request, spider):
# The order is very important for the following deferreds. Do not change!
# 1. Create the download deferred
dfd = mustbe_deferred(self.handlers.download_request, request, spider)
# 2. Notify response_downloaded listeners about the recent download
# before querying queue for next request
def _downloaded(response):
self.signals.send_catch_log(signal=signals.response_downloaded,
response=response,
request=request,
spider=spider)
return response
dfd.addCallback(_downloaded)
# 3. After response arrives, remove the request from transferring
# state to free up the transferring slot so it can be used by the
# following requests (perhaps those which came from the downloader
# middleware itself)
slot.transferring.add(request)
def finish_transferring(_):
slot.transferring.remove(request)
self._process_queue(spider, slot)
return _
return dfd.addBoth(finish_transferring)
def _download(self, slot, request, spider):
# The order is very important for the following deferreds. Do not change!
# 1. Create the download deferred
dfd = mustbe_deferred(self.handlers.download_request, request, spider)
# 2. Notify response_downloaded listeners about the recent download
# before querying queue for next request
def _downloaded(response):
self.signals.send_catch_log(
signal=signals.response_downloaded, response=response, request=request, spider=spider
)
return response
dfd.addCallback(_downloaded)
# 3. After response arrives, remove the request from transferring
# state to free up the transferring slot so it can be used by the
# following requests (perhaps those which came from the downloader
# middleware itself)
slot.transferring.add(request)
def finish_transferring(_):
slot.transferring.remove(request)
self._process_queue(spider, slot)
return _
return dfd.addBoth(finish_transferring)
def _process_request(self, request, info):
fp = request_fingerprint(request)
cb = request.callback or (lambda _: _)
eb = request.errback
request.callback = None
request.errback = None
# Return cached result if request was already seen
if fp in info.downloaded:
return defer_result(info.downloaded[fp]).addCallbacks(cb, eb)
# Otherwise, wait for result
wad = Deferred().addCallbacks(cb, eb)
info.waiting[fp].append(wad)
# Check if request is downloading right now to avoid doing it twice
if fp in info.downloading:
return wad
# Download request checking media_to_download hook output first
info.downloading.add(fp)
dfd = mustbe_deferred(self.media_to_download, request, info)
dfd.addCallback(self._check_media_to_download, request, info)
dfd.addBoth(self._cache_result_and_execute_waiters, fp, info)
dfd.addErrback(lambda f: logger.error(
f.value, exc_info=failure_to_exc_info(f), extra={'spider': info.spider})
)
return dfd.addBoth(lambda _: wad) # it must return wad at last
def download(self, request, spider):
def _on_success(response):
"""handle the result of a page download"""
assert isinstance(response, (Response, Request))
if isinstance(response, Response):
response.request = request # tie request to response received
log.msg(log.formatter.crawled(request, response, spider), \
level=log.DEBUG, spider=spider)
return response
elif isinstance(response, Request):
return mustbe_deferred(self.schedule, response, spider)
def _on_error(_failure):
"""handle an error processing a page"""
exc = _failure.value
if isinstance(exc, IgnoreRequest):
errmsg = _failure.getErrorMessage()
else:
errmsg = str(_failure)
if errmsg:
log.msg("Error downloading <%s>: %s" % (request.url, errmsg), \
level=log.ERROR, spider=spider)
return Failure(IgnoreRequest(str(exc)))
def _on_complete(_):
self.next_request(spider)
return _
if spider not in self.downloader.sites:
return defer.fail(Failure(IgnoreRequest())).addBoth(_on_complete)
dwld = mustbe_deferred(self.downloader.fetch, request, spider)
dwld.addCallbacks(_on_success, _on_error)
dwld.addBoth(_on_complete)
return dwld
def _process_request(self, request, info):
fp = request_fingerprint(request)
cb = request.callback or (lambda _: _)
eb = request.errback
request.callback = None
request.errback = None
# Return cached result if request was already seen
if fp in info.downloaded:
return defer_result(info.downloaded[fp]).addCallbacks(cb, eb)
# Otherwise, wait for result
wad = Deferred().addCallbacks(cb, eb)
info.waiting[fp].append(wad)
# Check if request is downloading right now to avoid doing it twice
if fp in info.downloading:
return wad
# Download request checking media_to_download hook output first
info.downloading.add(fp)
dfd = mustbe_deferred(self.media_to_download, request, info)
dfd.addCallback(self._check_media_to_download, request, info)
dfd.addBoth(self._cache_result_and_execute_waiters, fp, info)
dfd.addErrback(log.err, spider=info.spider)
return dfd.addBoth(lambda _: wad) # it must return wad at last
def _download(self, slot, request, spider):
# The order is very important for the following deferreds. Do not
# change!
# 1. Create the download deferred, 注册, 调用handlers的download_request, 发起真正下载
# 见scrapy/core/downloader/handlers/__init__.py, 这里注册并调用download_request.
# 其维护一个下载队列, 根据配置达到延时下载的目的
dfd = mustbe_deferred(self.handlers.download_request, request, spider)
# 2. Notify response_downloaded listeners about the recent download
# before querying queue for next request
# 注册回调方法:
def _downloaded(response):
self.signals.send_catch_log(signal=signals.response_downloaded,
response=response,
request=request,
spider=spider)
return response
dfd.addCallback(_downloaded)
# 3. After response arrives, remove the request from transferring
# state to free up the transferring slot so it can be used by the
# following requests (perhaps those which came from the downloader
# middleware itself)
slot.transferring.add(request) # 在返回响应之后, 移除request
def finish_transferring(_):
# 注册回调方法, response返回时
slot.transferring.remove(request)
# 下载完成后调用
self._process_queue(spider, slot)
return _
return dfd.addBoth(finish_transferring)
def download(self, download_func, request,
spider): # 这里的 download_func 实际就是downloader的_enqueue_request
@defer.inlineCallbacks
def process_request(request):
for method in self.methods['process_request']:
response = yield deferred_from_coro(
method(request=request, spider=spider)
) # 这个deferred_from_coro方法是将 middleware的方法 从 asyncio 转化为 recator方法 并yield出去
if response is not None and not isinstance(
response, (Response, Request)):
raise _InvalidOutput(
f"Middleware {method.__self__.__class__.__name__}"
".process_request must return None, Response or "
f"Request, got {response.__class__.__name__}")
if response:
return response
return (yield download_func(request=request, spider=spider))
@defer.inlineCallbacks
def process_response(response):
if response is None:
raise TypeError("Received None in process_response")
elif isinstance(response, Request):
return response
for method in self.methods['process_response']:
response = yield deferred_from_coro(
method(request=request, response=response, spider=spider))
if not isinstance(response, (Response, Request)):
raise _InvalidOutput(
f"Middleware {method.__self__.__class__.__name__}"
".process_response must return Response or Request, "
f"got {type(response)}")
if isinstance(response, Request):
return response
return response
@defer.inlineCallbacks
def process_exception(failure):
exception = failure.value
for method in self.methods['process_exception']:
response = yield deferred_from_coro(
method(request=request, exception=exception,
spider=spider))
if response is not None and not isinstance(
response, (Response, Request)):
raise _InvalidOutput(
f"Middleware {method.__self__.__class__.__name__}"
".process_exception must return None, Response or "
f"Request, got {type(response)}")
if response:
return response
return failure
deferred = mustbe_deferred(
process_request,
request) #类似于maybedeffered 但是不在这轮次里 运行callback 和 errback
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
def download(self, request, spider):
def _on_success(response):
"""handle the result of a page download"""
assert isinstance(response, (Response, Request))
if isinstance(response, Response):
response.request = request # tie request to response received
log.msg(log.formatter.crawled(request, response, spider), \
level=log.DEBUG, spider=spider)
return response
elif isinstance(response, Request):
return mustbe_deferred(self.schedule, response, spider)
def _on_error(_failure):
"""handle an error processing a page"""
exc = _failure.value
if isinstance(exc, IgnoreRequest):
errmsg = _failure.getErrorMessage()
else:
errmsg = str(_failure)
if errmsg:
log.msg("Error downloading <%s>: %s" % (request.url, errmsg), \
level=log.ERROR, spider=spider)
return Failure(IgnoreRequest(str(exc)))
def _on_complete(_):
self.next_request(spider)
return _
if spider not in self.downloader.sites:
return defer.fail(Failure(IgnoreRequest())).addBoth(_on_complete)
dwld = mustbe_deferred(self.downloader.fetch, request, spider)
dwld.addCallbacks(_on_success, _on_error)
dwld.addBoth(_on_complete)
return dwld
def _crawl(self, request):
dfd = mustbe_deferred(self._handler.download_request, request, None)
def downloaded(response, request):
result = {"status" : 600, "doc" : None, "headers" : None}
if isinstance(response, Response):
response = self._redirect_middleware.process_response(request, response, None)
if isinstance(response, Response):
result["url"] = response.url
result["status"] = response.status
result["doc"] = response.body
result["headers"] = response.headers
result["meta"] = request.meta
elif isinstance(response, Request):
redirect_time = response.meta.get("redirect_time", 0)
redirect_time += 1
if redirect_time >= 2:
result["url"] = response.url
result["status"] = 601
result["meta"] = response.meta
else:
result["url"] = response.url
result["status"] = 700
result["meta"] = response.meta
result["redirect_time"] = redirect_time
else:
raise Exception("not supported")
else:
result["url"] = request.url
result["error_message"] = "crawler failed:%s" % response
result["meta"] = request.meta
return result
return dfd.addBoth(downloaded, request)
def _download(self, request, info, fp):
def _downloaded(result):
info.downloading.pop(fp)
info.downloaded[fp] = result
for wad in info.waiting.pop(fp): # pass result to each waiting client
defer_result(result).chainDeferred(wad)
def _post_media_to_download(result):
if result is None: # continue with download
dwld = mustbe_deferred(self.download, request, info)
dwld.addCallbacks(
callback=self.media_downloaded,
callbackArgs=(request, info),
errback=self.media_failed,
errbackArgs=(request, info))
else: # or use media_to_download return value as result
dwld = defer_result(result)
info.downloading[fp] = (request, dwld) # fill downloading state data
dwld.addBoth(_downloaded) # append post-download hook
dwld.addErrback(log.err, spider=info.spider)
# declare request in downloading state (None is used as place holder)
info.downloading[fp] = None
# defer pre-download request processing
dfd = mustbe_deferred(self.media_to_download, request, info)
dfd.addCallback(_post_media_to_download)
def download(self, download_func: Callable, request: Request,
spider: Spider):
@defer.inlineCallbacks
def process_request(request: Request):
for method in self.methods['process_request']:
method = cast(Callable, method)
response = yield deferred_from_coro(
method(request=request, spider=spider))
if response is not None and not isinstance(
response, (Response, Request)):
raise _InvalidOutput(
f"Middleware {method.__qualname__} must return None, Response or "
f"Request, got {response.__class__.__name__}")
if response:
return response
return (yield download_func(request=request, spider=spider))
@defer.inlineCallbacks
def process_response(response: Union[Response, Request]):
if response is None:
raise TypeError("Received None in process_response")
elif isinstance(response, Request):
return response
for method in self.methods['process_response']:
method = cast(Callable, method)
response = yield deferred_from_coro(
method(request=request, response=response, spider=spider))
if not isinstance(response, (Response, Request)):
raise _InvalidOutput(
f"Middleware {method.__qualname__} must return Response or Request, "
f"got {type(response)}")
if isinstance(response, Request):
return response
return response
@defer.inlineCallbacks
def process_exception(failure: Failure):
exception = failure.value
for method in self.methods['process_exception']:
method = cast(Callable, method)
response = yield deferred_from_coro(
method(request=request, exception=exception,
spider=spider))
if response is not None and not isinstance(
response, (Response, Request)):
raise _InvalidOutput(
f"Middleware {method.__qualname__} must return None, Response or "
f"Request, got {type(response)}")
if response:
return response
return failure
deferred = mustbe_deferred(process_request, request)
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
def _next_request(self, spider):
# Next pending request from scheduler
request, deferred = self.scheduler.next_request(spider)
if request:
dwld = mustbe_deferred(self.download, request, spider)
dwld.chainDeferred(deferred).addBoth(lambda _: deferred)
dwld.addErrback(log.err, "Unhandled error on engine._next_request()",
spider=spider)
return dwld
def _check_media_to_download(self, result, request, info):
if result is not None:
return result
# Download request and process its response
return mustbe_deferred(self.download, request, info).addCallbacks(
callback=self.media_downloaded,
callbackArgs=(request, info),
errback=self.media_failed,
errbackArgs=(request, info))
def next_stage(item, stages_left):
assert isinstance(item, BaseItem), \
'Item pipelines must return a BaseItem, got %s' % type(item).__name__
if not stages_left:
return item
current_stage = stages_left.pop(0)
d = mustbe_deferred(current_stage.process_item, spider, item)
d.addCallback(next_stage, stages_left)
return d
def download(self, download_func, request, spider):
@defer.inlineCallbacks
def process_request(request):
for method in self.methods[
'process_request']: # 挨个执行下载器中间件的process_request方法
response = yield method(
request=request, spider=spider
) # 看，process_request方法就是在此处把requests和spider传入的
if response is not None and not isinstance(
response, (Response, Request)):
raise _InvalidOutput('Middleware %s.process_request must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, response.__class__.__name__))
if response:
defer.returnValue(response)
defer.returnValue(
(yield download_func(request=request, spider=spider)
)) # 如果下载器中间件没有返回值，则执行注册进来的方法，也就是Downloader的_enqueue_request
@defer.inlineCallbacks
def process_response(response):
assert response is not None, 'Received None in process_response'
if isinstance(response, Request):
defer.returnValue(response)
for method in self.methods['process_response']:
response = yield method(request=request,
response=response,
spider=spider)
if not isinstance(response, (Response, Request)):
raise _InvalidOutput('Middleware %s.process_response must return Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response)))
if isinstance(response, Request):
defer.returnValue(response)
defer.returnValue(response)
@defer.inlineCallbacks
def process_exception(_failure):
exception = _failure.value
for method in self.methods['process_exception']:
response = yield method(request=request,
exception=exception,
spider=spider)
if response is not None and not isinstance(
response, (Response, Request)):
raise _InvalidOutput('Middleware %s.process_exception must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response)))
if response:
defer.returnValue(response)
defer.returnValue(_failure)
deferred = mustbe_deferred(
process_request, request
) # 这里会马上调用process_request，处理完各个中间件的process_request方法，然后将request发出下载
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
def _on_success(response):
"""handle the result of a page download"""
assert isinstance(response, (Response, Request))
if isinstance(response, Response):
response.request = request # tie request to response received
log.msg(log.formatter.crawled(request, response, spider), \
level=log.DEBUG, spider=spider)
return response
elif isinstance(response, Request):
return mustbe_deferred(self.schedule, response, spider)
def _next_request(self, spider):
# Next pending request from scheduler
request, deferred = self.scheduler.next_request(spider)
if request:
dwld = mustbe_deferred(self.download, request, spider)
dwld.chainDeferred(deferred).addBoth(lambda _: deferred)
dwld.addErrback(log.err,
"Unhandled error on engine._next_request()",
spider=spider)
return dwld
def test_success_function(self):
steps = []
def _append(v):
steps.append(v)
return steps
dfd = mustbe_deferred(_append, 1)
dfd.addCallback(self.assertEqual, [1, 2]) # it is [1] with maybeDeferred
steps.append(2) # add another value, that should be catched by assertEqual
return dfd
def test_success_function(self):
steps = []
def _append(v):
steps.append(v)
return steps
dfd = mustbe_deferred(_append, 1)
dfd.addCallback(self.assertEqual, [1, 2]) # it is [1] with maybeDeferred
steps.append(2) # add another value, that should be catched by assertEqual
return dfd
def _on_success(response):
"""handle the result of a page download"""
assert isinstance(response, (Response, Request))
if isinstance(response, Response):
response.request = request # tie request to response received
log.msg(log.formatter.crawled(request, response, spider), \
level=log.DEBUG, spider=spider)
return response
elif isinstance(response, Request):
return mustbe_deferred(self.schedule, response, spider)
def download(self, download_func, request, spider):
@defer.inlineCallbacks
def process_request(request):
for method in self.methods['process_request']:
response = yield deferred_from_coro(
method(request=request, spider=spider))
if response is not None and not isinstance(
response, (Response, Request)):
raise _InvalidOutput(
"Middleware %s.process_request must return None, Response or Request, got %s"
% (method.__self__.__class__.__name__,
response.__class__.__name__))
if response:
defer.returnValue(response)
defer.returnValue((yield download_func(request=request,
spider=spider)))
@defer.inlineCallbacks
def process_response(response):
assert response is not None, 'Received None in process_response'
if isinstance(response, Request):
defer.returnValue(response)
for method in self.methods['process_response']:
response = yield deferred_from_coro(
method(request=request, response=response, spider=spider))
if not isinstance(response, (Response, Request)):
raise _InvalidOutput(
"Middleware %s.process_response must return Response or Request, got %s"
% (method.__self__.__class__.__name__, type(response)))
if isinstance(response, Request):
defer.returnValue(response)
defer.returnValue(response)
@defer.inlineCallbacks
def process_exception(_failure):
exception = _failure.value
for method in self.methods['process_exception']:
response = yield deferred_from_coro(
method(request=request, exception=exception,
spider=spider))
if response is not None and not isinstance(
response, (Response, Request)):
raise _InvalidOutput(
"Middleware %s.process_exception must return None, Response or Request, got %s"
% (method.__self__.__class__.__name__, type(response)))
if response:
defer.returnValue(response)
defer.returnValue(_failure)
deferred = mustbe_deferred(process_request, request)
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
def scrape_response(self, scrape_func, response, request, spider):
def process_callback_output(result):
return self._process_callback_output(response, spider, result)
def process_spider_exception(_failure):
return self._process_spider_exception(response, spider, _failure)
dfd = mustbe_deferred(self._process_spider_input, scrape_func,
response, request, spider)
dfd.addCallbacks(callback=process_callback_output,
errback=process_spider_exception)
return dfd
def test_unfired_deferred(self):
steps = []
def _append(v):
steps.append(v)
dfd = defer.Deferred()
reactor.callLater(0, dfd.callback, steps)
return dfd
dfd = mustbe_deferred(_append, 1)
dfd.addCallback(self.assertEqual, [1, 2]) # it is [1] with maybeDeferred
steps.append(2) # add another value, that should be catched by assertEqual
return dfd
def test_unfired_deferred(self):
steps = []
def _append(v):
steps.append(v)
dfd = defer.Deferred()
reactor.callLater(0, dfd.callback, steps)
return dfd
dfd = mustbe_deferred(_append, 1)
dfd.addCallback(self.assertEqual, [1, 2]) # it is [1] with maybeDeferred
steps.append(2) # add another value, that should be catched by assertEqual
return dfd
def download(self, download_func, request, spider):
@defer.inlineCallbacks
def process_request(request):
for method in self.methods['process_request']:
response = yield method(request=request, spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_request must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, response.__class__.__name__)
if response:
defer.returnValue(response)
try:
defer.returnValue((yield download_func(request=request,
spider=spider)))
except Exception as e:
with open('eroor', 'a') as w:
w.write(request.url + '\n')
@defer.inlineCallbacks
def process_response(response):
assert response is not None, 'Received None in process_response'
if isinstance(response, Request):
defer.returnValue(response)
for method in self.methods['process_response']:
response = yield method(request=request,
response=response,
spider=spider)
assert isinstance(response, (Response, Request)), \
'Middleware %s.process_response must return Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response))
if isinstance(response, Request):
defer.returnValue(response)
defer.returnValue(response)
@defer.inlineCallbacks
def process_exception(_failure):
exception = _failure.value
for method in self.methods['process_exception']:
response = yield method(request=request,
exception=exception,
spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_exception must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response))
if response:
defer.returnValue(response)
defer.returnValue(_failure)
deferred = mustbe_deferred(process_request, request)
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
def crawl(self, request, spider):
assert spider in self.open_spiders, \
"Spider %r not opened when crawling: %s" % (spider.name, request)
if spider in self.closing: # ignore requests for spiders being closed
return
schd = mustbe_deferred(self.schedule, request, spider)
# FIXME: we can't log errors because we would be preventing them from
# propagating to the request errback. This should be fixed after the
# next core refactoring.
#schd.addErrback(log.err, "Error on engine.crawl()")
schd.addBoth(self.scraper.enqueue_scrape, request, spider)
schd.addErrback(log.err, "Unhandled error on engine.crawl()", spider=spider)
schd.addBoth(lambda _: self.next_request(spider))
def _on_success(response):
"""handle the result of a page download"""
assert isinstance(response, (Response, Request))
if isinstance(response, Response):
response.request = request # tie request to response received
log.msg(self._crawled_logline(request, response), \
level=log.DEBUG, spider=spider)
return response
elif isinstance(response, Request):
newrequest = response
schd = mustbe_deferred(self.schedule, newrequest, spider)
schd.chainDeferred(newrequest.deferred)
return newrequest.deferred
def crawl(self, request, spider):
if not request.deferred.callbacks:
log.msg("Unable to crawl Request with no callback: %s" % request,
level=log.ERROR, spider=spider)
return
schd = mustbe_deferred(self.schedule, request, spider)
# FIXME: we can't log errors because we would be preventing them from
# propagating to the request errback. This should be fixed after the
# next core refactoring.
#schd.addErrback(log.err, "Error on engine.crawl()")
schd.addBoth(self.scraper.enqueue_scrape, request, spider)
schd.addErrback(log.err, "Unhandled error on engine.crawl()", spider=spider)
schd.addBoth(lambda _: self.next_request(spider))
def enqueue_request(self, wrappedfunc, spider, request):
def _enqueue_request(request):
for mwfunc in self.methods['enqueue_request']:
result = mwfunc(spider=spider, request=request)
assert result is None or isinstance(result, Deferred), \
'Middleware %s.enqueue_request must return None or Deferred, got %s' % \
(mwfunc.im_self.__class__.__name__, result.__class__.__name__)
if result:
return result
return wrappedfunc(spider=spider, request=request)
deferred = mustbe_deferred(_enqueue_request, request)
return deferred
def enqueue_request(self, wrappedfunc, spider, request):
def _enqueue_request(request):
for mwfunc in self.methods['enqueue_request']:
result = mwfunc(spider=spider, request=request)
assert result is None or isinstance(result, Deferred), \
'Middleware %s.enqueue_request must return None or Deferred, got %s' % \
(mwfunc.im_self.__class__.__name__, result.__class__.__name__)
if result:
return result
return wrappedfunc(spider=spider, request=request)
deferred = mustbe_deferred(_enqueue_request, request)
return deferred
def scrape_response(self, scrape_func, response, request, spider):
fname = lambda f: '%s.%s' % (six.get_method_self(f).__class__.__name__,
six.get_method_function(f).__name__)
def process_spider_input(response):
## 执行一系列爬虫中间件的 process_spider_input 方法
## 再执行 scrape_func 即 call_spider 方法
for method in self.methods['process_spider_input']:
try:
result = method(response=response, spider=spider)
assert result is None, \
'Middleware %s must returns None or ' \
'raise an exception, got %s ' \
% (fname(method), type(result))
except:
return scrape_func(Failure(), request, spider)
return scrape_func(response, request, spider)
def process_spider_exception(_failure):
## 执行一系列爬虫中间件的 process_spider_exception 方法
exception = _failure.value
for method in self.methods['process_spider_exception']:
result = method(response=response,
exception=exception,
spider=spider)
assert result is None or _isiterable(result), \
'Middleware %s must returns None, or an iterable object, got %s ' % \
(fname(method), type(result))
if result is not None:
return result
return _failure
def process_spider_output(result):
## 执行一系列爬虫中间件的 process_spider_output 方法
for method in self.methods['process_spider_output']:
result = method(response=response,
result=result,
spider=spider)
assert _isiterable(result), \
'Middleware %s must returns an iterable object, got %s ' % \
(fname(method), type(result))
return result
## 执行 process_spider_input 方法
dfd = mustbe_deferred(process_spider_input, response)
## 注册异常回调
dfd.addErrback(process_spider_exception)
## 注册出口回调
dfd.addCallback(process_spider_output)
return dfd
def _post_media_to_download(result):
if result is None: # continue with download
dwld = mustbe_deferred(self.download, request, info)
dwld.addCallbacks(
callback=self.media_downloaded,
callbackArgs=(request, info),
errback=self.media_failed,
errbackArgs=(request, info))
else: # or use media_to_download return value as result
dwld = defer_result(result)
info.downloading[fp] = (request, dwld) # fill downloading state data
dwld.addBoth(_downloaded) # append post-download hook
dwld.addErrback(log.err, spider=info.spider)
def scrape_response(self, scrape_func, response, request, spider):
fname = lambda f: '%s.%s' % (six.get_method_self(f).__class__.__name__,
six.get_method_function(f).__name__)
"""他会先执行完某一函数的所有回调情况，再往下走????whats???? 似乎每一个爬虫流程都会走一遍，whats
执行process_spider_input
执行call_spider
执行process_spider_output
"""
def process_spider_input(response):
for method in self.methods['process_spider_input']:
try:
result = method(response=response, spider=spider)
assert result is None, \
'Middleware %s must returns None or ' \
'raise an exception, got %s ' \
% (fname(method), type(result))
except:
return scrape_func(Failure(), request, spider)
return scrape_func(
response, request,
spider) # 这里就是call_spider爬虫处理后的结果，是一个dfd，里面指定了下一级的回调函数
def process_spider_exception(_failure): # 错了才会执行这里
exception = _failure.value
for method in self.methods['process_spider_exception']:
result = method(response=response,
exception=exception,
spider=spider)
assert result is None or _isiterable(result), \
'Middleware %s must returns None, or an iterable object, got %s ' % \
(fname(method), type(result))
if result is not None:
return result
return _failure
def process_spider_output(result):
for method in self.methods['process_spider_output']:
result = method(response=response,
result=result,
spider=spider)
assert _isiterable(result), \
'Middleware %s must returns an iterable object, got %s ' % \
(fname(method), type(result))
return result
dfd = mustbe_deferred(process_spider_input,
response) # 对进来的数据做一次处理???怎么还有这种操作
dfd.addErrback(process_spider_exception)
dfd.addCallback(process_spider_output)
return dfd
def scrape_response(self, scrape_func: ScrapeFunc, response: Response,
request: Request, spider: Spider) -> Deferred:
def process_callback_output(result: Iterable) -> MutableChain:
return self._process_callback_output(response, spider, result)
def process_spider_exception(
_failure: Failure) -> Union[Failure, MutableChain]:
return self._process_spider_exception(response, spider, _failure)
dfd = mustbe_deferred(self._process_spider_input, scrape_func,
response, request, spider)
dfd.addCallbacks(callback=process_callback_output,
errback=process_spider_exception)
return dfd
def _on_success(response):
"""handle the result of a page download"""
assert isinstance(response, (Response, Request))
if isinstance(response, Response):
response.request = request # tie request to response received
log.msg(self._crawled_logline(request, response), \
level=log.DEBUG, spider=spider)
return response
elif isinstance(response, Request):
newrequest = response
dfd = mustbe_deferred(self.schedule, newrequest, spider)
if newrequest.callback:
# XXX: this is a bit hacky and should be removed
dfd.addCallbacks(newrequest.callback, newrequest.errback)
return dfd
def crawl(self, request, spider):
if spider in self.closing: # ignore requests for spiders being closed
return
assert spider in self.open_spiders, \
"Spider %r not opened when crawling: %s" % (spider.name, request)
schd = mustbe_deferred(self.schedule, request, spider)
# FIXME: we can't log errors because we would be preventing them from
# propagating to the request errback. This should be fixed after the
# next core refactoring.
#schd.addErrback(log.err, "Error on engine.crawl()")
schd.addBoth(self.scraper.enqueue_scrape, request, spider)
schd.addErrback(log.err,
"Unhandled error on engine.crawl()",
spider=spider)
schd.addBoth(lambda _: self.next_request(spider))
def download(self, download_func, request, spider):
@defer.inlineCallbacks
def process_request(request):
for method in self.methods['process_request']:
# splash request , dont process again by wsy
if request.meta.get("_splash_processed"):
break
response = yield method(request=request, spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_request must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, response.__class__.__name__)
if response:
defer.returnValue(response)
defer.returnValue((yield download_func(request=request,spider=spider)))
@defer.inlineCallbacks
def process_response(response):
assert response is not None, 'Received None in process_response'
if isinstance(response, Request):
defer.returnValue(response)
for method in self.methods['process_response']:
response = yield method(request=request, response=response,
spider=spider)
assert isinstance(response, (Response, Request)), \
'Middleware %s.process_response must return Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response))
if isinstance(response, Request):
defer.returnValue(response)
defer.returnValue(response)
@defer.inlineCallbacks
def process_exception(_failure):
exception = _failure.value
for method in self.methods['process_exception']:
response = yield method(request=request, exception=exception,
spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_exception must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response))
if response:
defer.returnValue(response)
defer.returnValue(_failure)
deferred = mustbe_deferred(process_request, request)
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
def _check_media_to_download(self, result, request, info):
if result is not None:
return result
if self.download_func:
# this ugly code was left only to support tests. TODO: remove
dfd = mustbe_deferred(self.download_func, request, info.spider)
dfd.addCallbacks(
callback=self.media_downloaded, callbackArgs=(request, info),
errback=self.media_failed, errbackArgs=(request, info))
else:
request.meta['handle_httpstatus_all'] = True
dfd = self.crawler.engine.download(request, info.spider)
dfd.addCallbacks(
callback=self.media_downloaded, callbackArgs=(request, info),
errback=self.media_failed, errbackArgs=(request, info))
return dfd
def _check_media_to_download(self, result, request, info):
if result is not None:
return result
if self.download_func:
# this ugly code was left only to support tests. TODO: remove
dfd = mustbe_deferred(self.download_func, request, info.spider)
dfd.addCallbacks(
callback=self.media_downloaded, callbackArgs=(request, info),
errback=self.media_failed, errbackArgs=(request, info))
else:
self._modify_media_request(request)
dfd = self.crawler.engine.download(request, info.spider)
dfd.addCallbacks(
callback=self.media_downloaded, callbackArgs=(request, info),
errback=self.media_failed, errbackArgs=(request, info))
return dfd
def _download(self, site, request, spider):
# The order is very important for the following deferreds. Do not change!
# 1. Create the download deferred
dfd = mustbe_deferred(self.handlers.download_request, request, spider)
# 2. After response arrives, remove the request from transferring
# state to free up the transferring slot so it can be used by the
# following requests (perhaps those which came from the downloader
# middleware itself)
site.transferring.add(request)
def finish_transferring(_):
site.transferring.remove(request)
self._process_queue(spider)
return _
return dfd.addBoth(finish_transferring)
def download(self, download_func, request, spider):
@defer.inlineCallbacks
def process_request(request):
for method in self.methods["process_request"]:
response = yield method(request=request, spider=spider)
assert response is None or isinstance(response, (Response, Request)), (
"Middleware %s.process_request must return None, Response or Request, got %s"
% (six.get_method_self(method).__class__.__name__, response.__class__.__name__)
)
if response:
defer.returnValue(response)
defer.returnValue((yield download_func(request=request, spider=spider)))
@defer.inlineCallbacks
def process_response(response):
assert response is not None, "Received None in process_response"
if isinstance(response, Request):
defer.returnValue(response)
for method in self.methods["process_response"]:
response = yield method(request=request, response=response, spider=spider)
assert isinstance(response, (Response, Request)), (
"Middleware %s.process_response must return Response or Request, got %s"
% (six.get_method_self(method).__class__.__name__, type(response))
)
if isinstance(response, Request):
defer.returnValue(response)
defer.returnValue(response)
@defer.inlineCallbacks
def process_exception(_failure):
exception = _failure.value
for method in self.methods["process_exception"]:
response = yield method(request=request, exception=exception, spider=spider)
assert response is None or isinstance(response, (Response, Request)), (
"Middleware %s.process_exception must return None, Response or Request, got %s"
% (six.get_method_self(method).__class__.__name__, type(response))
)
if response:
defer.returnValue(response)
defer.returnValue(_failure)
deferred = mustbe_deferred(process_request, request)
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
def download(self, download_func, request, spider):
@defer.inlineCallbacks
def process_request(request):
for method in self.methods['process_request']:
response = yield method(request=request, spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_request must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, response.__class__.__name__) # 规定返回类型，None，response，request这三种
if response: # 如果是空，则会继续处理所有的中间件，但是一旦不是了，就会提前跑路，对，应该就是这个意思，可以很骚
defer.returnValue(response)
defer.returnValue((yield download_func(request=request,spider=spider)))
@defer.inlineCallbacks
def process_response(response):
assert response is not None, 'Received None in process_response'
if isinstance(response, Request):
defer.returnValue(response)
for method in self.methods['process_response']:
response = yield method(request=request, response=response,
spider=spider)
assert isinstance(response, (Response, Request)), \
'Middleware %s.process_response must return Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response))
if isinstance(response, Request):
defer.returnValue(response)
defer.returnValue(response)
@defer.inlineCallbacks
def process_exception(_failure):
exception = _failure.value
for method in self.methods['process_exception']:
response = yield method(request=request, exception=exception,
spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_exception must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response))
if response:
defer.returnValue(response)
defer.returnValue(_failure)
deferred = mustbe_deferred(process_request, request) # 执行顺序，现执行request，再执行exception，最后才是response
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
def _download(self, slot, request, spider):
# The order is very important for the following deferreds. Do not change!
# 1. Create the download deferred
dfd = mustbe_deferred(self.handlers.download_request, request, spider)
# 2. After response arrives, remove the request from transferring
# state to free up the transferring slot so it can be used by the
# following requests (perhaps those which came from the downloader
# middleware itself)
slot.transferring.add(request)
def finish_transferring(_):
slot.transferring.remove(request)
self._process_queue(spider, slot)
return _
return dfd.addBoth(finish_transferring)
def scrape_response(self, scrape_func: ScrapeFunc, response: Response,
request: Request, spider: Spider) -> Deferred:
async def process_callback_output(
result: Union[Iterable, AsyncIterable]
) -> Union[MutableChain, MutableAsyncChain]:
return await self._process_callback_output(response, spider,
result)
def process_spider_exception(
_failure: Failure) -> Union[Failure, MutableChain]:
return self._process_spider_exception(response, spider, _failure)
dfd = mustbe_deferred(self._process_spider_input, scrape_func,
response, request, spider)
dfd.addCallbacks(
callback=deferred_f_from_coro_f(process_callback_output),
errback=process_spider_exception)
return dfd
def _download(self, slot, request, spider):
# The order is very important for the following deferreds. Do not change!
request.meta['the_id_from_scrapy'] = 0
# 1. Create the download deferred
def download_request(request, spider):
starttime = str(datetime.datetime.now())
request.meta['the_id_from_scrapy'] = self.write_database_start(spider.name, starttime)
return self.handlers[spider.name].download_request(request, spider)
dfd = mustbe_deferred(download_request, request, spider)
# 2. Notify response_downloaded listeners about the recent download
# before querying queue for next request
def _downloaded(response):
size = len(str(response.body))
self.write_database_end(request.meta['the_id_from_scrapy'], str(datetime.datetime.now()), size)
self.signals[spider.name].send_catch_log(signal=signals.response_downloaded,
response=response,
request=request,
spider=spider)
return response
dfd.addCallback(_downloaded)
def _err_handle(response):
self.delete_bad_with_id(request.meta['the_id_from_scrapy'])
return response
dfd.addErrback(_err_handle)
# 3. After response arrives, remove the request from transferring
# state to free up the transferring slot so it can be used by the
# following requests (perhaps those which came from the downloader
# middleware itself)
slot.transferring.add(request)
def finish_transferring(_):
slot.transferring.remove(request)
self._process_queue(spider, slot)
return _
return dfd.addBoth(finish_transferring)
def download(self, download_func, request, spider):
def process_request(request):
for method in self.methods['process_request']:
response = method(request=request, spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_request must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, response.__class__.__name__)
if response:
return response
return download_func(request=request, spider=spider)
def process_response(response):
assert response is not None, 'Received None in process_response'
if isinstance(response, Request):
return response
for method in self.methods['process_response']:
response = method(request=request,
response=response,
spider=spider)
assert isinstance(response, (Response, Request)), \
'Middleware %s.process_response must return Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response))
if isinstance(response, Request):
return response
return response
def process_exception(_failure):
exception = _failure.value
for method in self.methods['process_exception']:
response = method(request=request,
exception=exception,
spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_exception must return None, Response or Request, got %s' % \
(six.get_method_self(method).__class__.__name__, type(response))
if response:
return response
return _failure
deferred = mustbe_deferred(process_request, request)
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
def download(self, download_func, request, spider):
def process_request(request):
for method in self.request_middleware:
response = method(request=request, spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_request must return None, Response or Request, got %s' % \
(method.im_self.__class__.__name__, response.__class__.__name__)
if response:
return response
return download_func(request=request, spider=spider)
def process_response(response):
assert response is not None, 'Received None in process_response'
if isinstance(response, Request):
return response
for method in self.response_middleware:
response = method(request=request, response=response, spider=spider)
assert isinstance(response, (Response, Request)), \
'Middleware %s.process_response must return Response or Request, got %s' % \
(method.im_self.__class__.__name__, type(response))
if isinstance(response, Request):
send_catch_log(signal=signals.response_received, \
sender=self.__class__, response=response, spider=spider)
return response
send_catch_log(signal=signals.response_received, sender=self.__class__, \
response=response, spider=spider)
return response
def process_exception(_failure):
exception = _failure.value
for method in self.exception_middleware:
response = method(request=request, exception=exception, spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_exception must return None, Response or Request, got %s' % \
(method.im_self.__class__.__name__, type(response))
if response:
return response
return _failure
deferred = mustbe_deferred(process_request, request)
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
def process_pokemon_request(self, request, info):
fingerprint = request_fingerprint(request)
callback = request.callback or (lambda _: _)
errorback = request.errback
request.callback = None
request.errback = None
# Otherwise, wait for result
wad = Deferred().addCallbacks(callback, errorback)
info.waiting[fingerprint].append(wad)
info.downloading.add(fingerprint)
dfd = mustbe_deferred(self.media_to_download, request, info)
dfd.addCallback(self._check_media_to_download, request, info)
dfd.addBoth(self._cache_result_and_execute_waiters, fingerprint, info)
dfd.addErrback(lambda f: logger.error(f.value,
exc_info=failure_to_exc_info(f),
extra={'spider': info.spider}))
return dfd.addBoth(lambda _: wad) # it must return wad at last
def scrape_response(self, scrape_func, response, request, spider):
fname = lambda f: '%s.%s' % (f.im_self.__class__.__name__, f.im_func.
__name__)
def process_spider_input(response):
for method in self.methods['process_spider_input']:
try:
result = method(response=response, spider=spider)
assert result is None, \
'Middleware %s must returns None or ' \
'raise an exception, got %s ' \
% (fname(method), type(result))
except:
return scrape_func(Failure(), request, spider)
return scrape_func(response, request, spider)
def process_spider_exception(_failure):
exception = _failure.value
for method in self.methods['process_spider_exception']:
result = method(response=response,
exception=exception,
spider=spider)
assert result is None or _isiterable(result), \
'Middleware %s must returns None, or an iterable object, got %s ' % \
(fname(method), type(result))
if result is not None:
return result
return _failure
def process_spider_output(result):
for method in self.methods['process_spider_output']:
result = method(response=response,
result=result,
spider=spider)
assert _isiterable(result), \
'Middleware %s must returns an iterable object, got %s ' % \
(fname(method), type(result))
return result
dfd = mustbe_deferred(process_spider_input, response)
dfd.addErrback(process_spider_exception)
dfd.addCallback(process_spider_output)
return dfd
def download(self, download_func, request, spider):
def process_request(request):
for method in self.methods['process_request']:
response = method(request=request, spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_request must return None, Response or Request, got %s' % \
(method.im_self.__class__.__name__, response.__class__.__name__)
if response:
return response
return download_func(request=request, spider=spider)
def process_response(response):
assert response is not None, 'Received None in process_response'
if isinstance(response, Request):
return response
for method in self.methods['process_response']:
try:
response = method(request=request, response=response, spider=spider)
except:
return process_exception(Failure())
assert isinstance(response, (Response, Request)), \
'Middleware %s.process_response must return Response or Request, got %s' % \
(method.im_self.__class__.__name__, type(response))
if isinstance(response, Request):
return response
return response
def process_exception(_failure):
exception = _failure.value
for method in self.methods['process_exception']:
response = method(request=request, exception=exception, spider=spider)
assert response is None or isinstance(response, (Response, Request)), \
'Middleware %s.process_exception must return None, Response or Request, got %s' % \
(method.im_self.__class__.__name__, type(response))
if response:
return response
return _failure
deferred = mustbe_deferred(process_request, request)
deferred.addErrback(process_exception)
deferred.addCallback(process_response)
return deferred
def download(self, request, spider):
def _on_success(response):
"""handle the result of a page download"""
assert isinstance(response, (Response, Request))
if isinstance(response, Response):
response.request = request # tie request to response received
log.msg(self._crawled_logline(request, response), \
level=log.DEBUG, spider=spider)
return response
elif isinstance(response, Request):
newrequest = response
dfd = mustbe_deferred(self.schedule, newrequest, spider)
if newrequest.callback:
# XXX: this is a bit hacky and should be removed
dfd.addCallbacks(newrequest.callback, newrequest.errback)
return dfd
def _on_error(_failure):
"""handle an error processing a page"""
exc = _failure.value
if isinstance(exc, IgnoreRequest):
errmsg = _failure.getErrorMessage()
level = exc.level
else:
errmsg = str(_failure)
level = log.ERROR
if errmsg:
log.msg("Crawling <%s>: %s" % (request.url, errmsg), \
level=level, spider=spider)
return Failure(IgnoreRequest(str(exc)))
def _on_complete(_):
self.next_request(spider)
return _
if spider not in self.downloader.sites:
return defer.fail(Failure(IgnoreRequest())).addBoth(_on_complete)
dwld = mustbe_deferred(self.downloader.fetch, request, spider)
dwld.addCallbacks(_on_success, _on_error)
dwld.addBoth(_on_complete)
return dwld
def scrape_response(self, scrape_func, response, request, spider):
fname = lambda f: '%s.%s' % (
f.im_self.__class__.__name__, f.im_func.__name__)
def process_spider_input(response):
for method in self.methods['process_spider_input']:
try:
result = method(response=response, spider=spider)
assert result is None, \
'Middleware %s must returns None or ' \
'raise an exception, got %s ' \
% (fname(method), type(result))
except:
return scrape_func(Failure(), request, spider)
return scrape_func(response, request, spider)
def process_spider_exception(_failure):
exception = _failure.value
for method in self.methods['process_spider_exception']:
result = method(
response=response, exception=exception, spider=spider)
assert result is None or _isiterable(result), \
'Middleware %s must returns None, or an iterable object, got %s ' % \
(fname(method), type(result))
if result is not None:
return result
return _failure
def process_spider_output(result):
for method in self.methods['process_spider_output']:
result = method(
response=response, result=result, spider=spider)
assert _isiterable(result), \
'Middleware %s must returns an iterable object, got %s ' % \
(fname(method), type(result))
return result
dfd = mustbe_deferred(process_spider_input, response)
dfd.addErrback(process_spider_exception)
dfd.addCallback(process_spider_output)
return dfd
def _download(self, request, spider):
slot = self.slots[spider]
slot.add_request(request)
def _on_success(response):
"""handle the result of a page download"""
assert isinstance(response, (Response, Request))
if isinstance(response, Response):
response.request = request # tie request to response received
log.msg(log.formatter.crawled(request, response, spider), \
level=log.DEBUG, spider=spider)
send_catch_log(signal=signals.response_received, \
response=response, request=request, spider=spider)
return response
def _on_complete(_):
self.next_request(spider)
return _
dwld = mustbe_deferred(self.downloader.fetch, request, spider)
dwld.addCallback(_on_success)
dwld.addBoth(_on_complete)
return dwld
def _download(self, site, request, spider):
# The order is very important for the following deferreds. Do not change!
# 1. Create the download deferred
dfd = mustbe_deferred(download_any, request, spider)
# 2. After response arrives, remove the request from transferring
# state to free up the transferring slot so it can be used by the
# following requests (perhaps those which came from the downloader
# middleware itself)
site.transferring.add(request)
def finish_transferring(_):
site.transferring.remove(request)
self._process_queue(spider)
# avoid partially downloaded responses from propagating to the
# downloader middleware, to speed-up the closing process
if site.closing:
log.msg("Crawled while closing spider: %s" % request, \
level=log.DEBUG, spider=spider)
raise IgnoreRequest
return _
return dfd.addBoth(finish_transferring)
def _download(self, slot, request, spider):
# The order is very important for the following deferreds. Do not change!
# 1. Create the download deferred
dfd = mustbe_deferred(self.handlers.download_request, request, spider)
# 2. Notify response_downloaded listeners about the recent download
# before querying queue for next request
# 在查询队列中的下一个请求之前，通知response_downloaded的侦听器有关最近的下载的信息
def _downloaded(response):
# s.response_downloaded 正在获取响应的位置
self.signals.send_catch_log(signal=signals.response_downloaded,
response=response,
request=request,
spider=spider)
return response
dfd.addCallback(_downloaded)
# 3. After response arrives, remove the request from transferring
# state to free up the transferring slot so it can be used by the
# following requests (perhaps those which came from the downloader
# middleware itself)
# 响应到达后，将请求从传输状态中删除以释放传输插槽，以便随后的请求可以使用它（也许来自下载器中间件本身的请求）
slot.transferring.add(request)
def finish_transferring(_):
slot.transferring.remove(request)
self._process_queue(spider, slot)
# s.request_left_downloader 刚离开下载器
self.signals.send_catch_log(signal=signals.request_left_downloader,
request=request,
spider=spider)
return _
return dfd.addBoth(finish_transferring)
def _download(self, site, request, spider):
# The order is very important for the following deferreds. Do not change!
# 1. Create the download deferred
dfd = mustbe_deferred(self.handlers.download_request, request, spider)
# 2. After response arrives, remove the request from transferring
# state to free up the transferring slot so it can be used by the
# following requests (perhaps those which came from the downloader
# middleware itself)
site.transferring.add(request)
def finish_transferring(_):
site.transferring.remove(request)
self._process_queue(spider)
# avoid partially downloaded responses from propagating to the
# downloader middleware, to speed-up the closing process
if site.closing:
log.msg("Crawled while closing spider: %s" % request, \
level=log.DEBUG, spider=spider)
raise IgnoreRequest
return _
return dfd.addBoth(finish_transferring)
def scrape_response(self, scrape_func, response, request, spider):
#scrapy_func是什么东西？？
fname = lambda f:'%s.%s' % (f.im_self.__class__.__name__, f.im_func.__name__)
#fname(f):传入f
#返回f.im_self.__class__.__name__ 和f.im_func.__name__连接的字符串。
def process_spider_input(response):
#依次调用methods中存入的，所有中间件中的process_spider_input方法。
for method in self.methods['process_spider_input']:
try:
result = method(response=response, spider=spider)
#每一个中间件处理input完成的result没有记录或者处理
#process_spider_inpurt1,2,3,4,5,6...(response,spider)
assert result is None, \
'Middleware %s must returns None or ' \
'raise an exception, got %s ' \
% ( fname(method), type( result ) )
#如果result为None，则表示调用成功。
#猜测：可能repsonse在process中已经被修改了某些部分，
#所以没有必要记录返回的result。
except:
return scrape_func(Failure(), request, spider)
#猜测：如果有一个中间件执行错误。应该是调用错误回调。
#猜测：Failure()实例作为input（或者result)返回到下一错误链。
return scrape_func(response, request, spider)
#猜测：如果执行正确，则以response为input（或者result）返回到回调链。
def process_spider_exception(_failure):
exception = _failure.value
#exception
for method in self.methods['process_spider_exception']:
result = method(response=response, exception=exception, spider=spider)
assert result is None or _isiterable(result), \
'Middleware %s must returns None, or an iterable object, got %s ' % \
(fname(method), type(result))
#如果不是None，就从链中断开，直接返回result。
#猜测：这个result会不会返回到callback？？
if result is not None:
return result
return _failure
def process_spider_output(result):
for method in self.methods['process_spider_output']:
result = method(response=response, result=result, spider=spider)
assert _isiterable(result), \
'Middleware %s must returns an iterable object, got %s ' % \
(fname(method), type(result))
return result
dfd = mustbe_deferred(process_spider_input, response)
#mustbe_deffered:首先调用result = process_spider_input(response)
#出错就一会调用errback
#result没问题则调用下一轮处理result的延迟。
dfd.addErrback(process_spider_exception)
#添加errback
dfd.addCallback(process_spider_output)
#添加callback
return dfd
def scrape_response(self, scrape_func, response, request, spider):
fname = lambda f:'%s.%s' % (
six.get_method_self(f).__class__.__name__,
six.get_method_function(f).__name__)
def process_spider_input(response):
for method in self.methods['process_spider_input']:
try:
result = method(response=response, spider=spider)
if result is not None:
raise _InvalidOutput('Middleware {} must return None or raise an exception, got {}' \
.format(fname(method), type(result)))
except _InvalidOutput:
raise
except Exception:
return scrape_func(Failure(), request, spider)
return scrape_func(response, request, spider)
def process_spider_exception(_failure, start_index=0):
exception = _failure.value
# don't handle _InvalidOutput exception
if isinstance(exception, _InvalidOutput):
return _failure
method_list = islice(self.methods['process_spider_exception'], start_index, None)
for method_index, method in enumerate(method_list, start=start_index):
if method is None:
continue
result = method(response=response, exception=exception, spider=spider)
if _isiterable(result):
# stop exception handling by handing control over to the
# process_spider_output chain if an iterable has been returned
return process_spider_output(result, method_index+1)
elif result is None:
continue
else:
raise _InvalidOutput('Middleware {} must return None or an iterable, got {}' \
.format(fname(method), type(result)))
return _failure
def process_spider_output(result, start_index=0):
# items in this iterable do not need to go through the process_spider_output
# chain, they went through it already from the process_spider_exception method
recovered = MutableChain()
def evaluate_iterable(iterable, index):
try:
for r in iterable:
yield r
except Exception as ex:
exception_result = process_spider_exception(Failure(ex), index+1)
if isinstance(exception_result, Failure):
raise
recovered.extend(exception_result)
method_list = islice(self.methods['process_spider_output'], start_index, None)
for method_index, method in enumerate(method_list, start=start_index):
if method is None:
continue
# the following might fail directly if the output value is not a generator
try:
result = method(response=response, result=result, spider=spider)
except Exception as ex:
exception_result = process_spider_exception(Failure(ex), method_index+1)
if isinstance(exception_result, Failure):
raise
return exception_result
if _isiterable(result):
result = evaluate_iterable(result, method_index)
else:
raise _InvalidOutput('Middleware {} must return an iterable, got {}' \
.format(fname(method), type(result)))
return chain(result, recovered)
dfd = mustbe_deferred(process_spider_input, response)
dfd.addCallbacks(callback=process_spider_output, errback=process_spider_exception)
return dfd
def fetch(self, url):
log.debug("Fetch URL %s" % url)
request = Request(url=url)
self.process_request(request)
return mustbe_deferred(self.downloader.download_request, request, None)
