Issue discussed here https://github.com/scrapinghub/frontera/issues/211#issuecomment-251931413 Todo List

• [X] Fix msgpack codec
• [x] Fix json codec
• [x] Integration test with Hbase backend(manually)

This PR fixes #211

Other things done in this besides the todo list:

• Added two methods _convert and reconvert in json codec. These are needed as JSONEncoder accepts strings only as unicode. Method convert converts objects recursively to unicode and saves their type.
• made the requirement of msgpack >=0.4 as only versions greater than 0.4 support the changes made in this PR.
• fixed a buggy test case in test_message_bus_backend which got exposed after fixing the codecs.

The documentation is a little simple and does not explain how to integrate with Kafka and Hbase for a fully distributed architecture. Could you, please provide an example in the examples folder of a well configured distributed frontera config?

Most of the changes were produced using the modernize script. Changes include print syntax, error syntax, converting iterators and generators to lists, etc. Also includes some other changes which were missed by the script.

I am using the development version of distributed-frontera, frontera and scrapy for crawling. After a while my spider keeps getting stuck in a redirect loop. Restarting the spider helps, but after a while this happens:

2015-12-21 17:23:22 [scrapy] INFO: Crawled 10354 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2015-12-21 17:23:22 [scrapy] DEBUG: Redirecting (302) to <GET http://www.reg.ru/domain/new-gtlds> from <GET http://www.reg.ru/domain/new-gtlds>
2015-12-21 17:23:22 [scrapy] DEBUG: Redirecting (302) to <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit> from <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit>
2015-12-21 17:23:22 [scrapy] DEBUG: Redirecting (302) to <GET http://www.reg.ru/domain/new-gtlds> from <GET http://www.reg.ru/domain/new-gtlds>
2015-12-21 17:23:23 [scrapy] DEBUG: Redirecting (302) to <GET http://www.reg.ru/domain/new-gtlds> from <GET http://www.reg.ru/domain/new-gtlds>
2015-12-21 17:23:24 [scrapy] DEBUG: Redirecting (302) to <GET http://www.reg.ru/domain/new-gtlds> from <GET http://www.reg.ru/domain/new-gtlds>
2015-12-21 17:23:25 [scrapy] DEBUG: Redirecting (302) to <GET http://www.reg.ru/domain/new-gtlds> from <GET http://www.reg.ru/domain/new-gtlds>
2015-12-21 17:23:25 [scrapy] DEBUG: Redirecting (302) to <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit> from <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit>
2015-12-21 17:23:25 [scrapy] DEBUG: Redirecting (302) to <GET http://www.reg.ru/domain/new-gtlds> from <GET http://www.reg.ru/domain/new-gtlds>
2015-12-21 17:23:26 [scrapy] DEBUG: Redirecting (302) to <GET http://www.reg.ru/domain/new-gtlds> from <GET http://www.reg.ru/domain/new-gtlds>
2015-12-21 17:23:27 [scrapy] DEBUG: Redirecting (302) to <GET http://www.reg.ru/domain/new-gtlds> from <GET http://www.reg.ru/domain/new-gtlds>
2015-12-21 17:23:32 [scrapy] INFO: Crawled 10354 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2015-12-21 17:23:32 [scrapy] DEBUG: Redirecting (302) to <GET http://www.reg.ru/domain/new-gtlds> from <GET http://www.reg.ru/domain/new-gtlds>
2015-12-21 17:23:32 [scrapy] DEBUG: Redirecting (302) to <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit> from <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit>
2015-12-21 17:23:33 [scrapy] DEBUG: Discarding <GET http://www.reg.ru/domain/new-gtlds>: max redirections reached
2015-12-21 17:23:34 [scrapy] DEBUG: Discarding <GET http://www.reg.ru/domain/new-gtlds>: max redirections reached
2015-12-21 17:23:34 [scrapy] DEBUG: Discarding <GET http://www.reg.ru/domain/new-gtlds>: max redirections reached
2015-12-21 17:23:35 [scrapy] DEBUG: Discarding <GET http://www.reg.ru/domain/new-gtlds>: max redirections reached
2015-12-21 17:23:35 [scrapy] DEBUG: Redirecting (302) to <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit> from <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit>
2015-12-21 17:23:36 [scrapy] DEBUG: Discarding <GET http://www.reg.ru/domain/new-gtlds>: max redirections reached
2015-12-21 17:23:37 [scrapy] DEBUG: Discarding <GET http://www.reg.ru/domain/new-gtlds>: max redirections reached
2015-12-21 17:23:38 [scrapy] DEBUG: Redirecting (302) to <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit> from <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit>
2015-12-21 17:23:43 [scrapy] INFO: Crawled 10354 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2015-12-21 17:23:43 [scrapy] DEBUG: Redirecting (302) to <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit> from <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit>
...
2015-12-21 17:45:38 [scrapy] DEBUG: Redirecting (302) to <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit> from <GET http://www.toraath.com/index.php?lid=35&name=Downloads&req=getit>
2015-12-21 17:45:43 [scrapy] INFO: Crawled 10354 pages (at 0 pages/min), scraped 0 items (at 0 items/min)

This does not seem to be an issue with distributed-frontera since I could not find any code related to redirecting there.

This PR is a rebase of #128. Although I have completely changed the design and refactored the code, I have added @wpxgit commits(but squashed them) because this work was originally initiated by him.

I have tried to follow the DRY methodology as much as possible, so I had to refactor some existing code.

I have serialized dicts using Pickle, as a result this backend won't have problems discussed in #211.

The PR includes unit tests and some integration tests with the backends integration testing framework.

Its good that frontera has an integration test framework for testing backends in single threaded mode. However, having a similar framework for the distributed mode is very much needed.

I am open to all sorts of suggestions :)

Hi, Im trying to use cluster configuration. I've created topics in kafka and have it up and running. Im running into trouble starting the database worker. Tried: python -m frontera.worker.db --config config.dbw --no-incoming --partitions 0,1 got an error 0,1 not recognized, tried: python -m frontera.worker.db --config config.dbw --no-incoming --partitions 0 I was getting the same issue as in #359, but somehow that stopped happening.

Now I'm getting: that kafka partitions are not recognized or iterrable, see error. Im using python 3.6 and the frontera from the repo (FYI qzm and cachetools still needed to be installed manually). Any ideas?

File "/usr/lib64/python3.6/runpy.py", line 193, in _run_module_as_main "main", mod_spec) File "/usr/lib64/python3.6/runpy.py", line 85, in _run_code exec(code, run_globals) File "/usr/lib/python3.6/dist-packages/frontera/worker/db.py", line 246, in args.no_scoring, partitions=args.partitions) File "/usr/lib/python3.6/dist-packages/frontera/worker/stats.py", line 22, in init super(StatsExportMixin, self).init(settings, *args, **kwargs) File "/usr/lib/python3.6/dist-packages/frontera/worker/db.py", line 115, in init self.slot = Slot(self, settings, **slot_kwargs) File "/usr/lib/python3.6/dist-packages/frontera/worker/db.py", line 46, in init self.components = self._load_components(worker, settings, **kwargs) File "/usr/lib/python3.6/dist-packages/frontera/worker/db.py", line 55, in _load_components component = cls(worker, settings, stop_event=self.stop_event, **kwargs) File "/usr/lib/python3.6/dist-packages/frontera/worker/components/scoring_consumer.py", line 24, in init self.scoring_log_consumer = scoring_log.consumer() File "/usr/lib/python3.6/dist-packages/frontera/contrib/messagebus/kafkabus.py", line 219, in consumer return Consumer(self._location, self._enable_ssl, self._cert_path, self._topic, self._group, partition_id=None) File "/usr/lib/python3.6/dist-packages/frontera/contrib/messagebus/kafkabus.py", line 60, in init self._partitions = [TopicPartition(self._topic, pid) for pid in self._consumer.partitions_for_topic(self._topic)]

Imagine, we have a queue of 10K urls from many different domains. Our task is to fetch it as fast as possible. At the same time we have a prioritization which tends to group URLs from the same domain. During downloading we want to be polite and limit per host RPS. So, picking just top URLs from the queue leeds us to the time waste, because connection pool of Scrapy downloader most of time underused.

In this PR, I'm addressing this issue by propagating information about overused hostnames/IPs in downloader pool.

fixes #253 Here's a screenshot using the same code discussed here.

Nothing seems to break when testing this change manually. The only test that was failing was wrong IMO because it passed a list of requests and items and was only expecting items in return. I have modified that test to make it compatible with this patch.

I've the split this PR into three commits:

• The first commit adds a test to reproduce the bug.
• The second commit fixes the bug
• The third commit fixes the broken test discussed above

A note about the tests added:

• https://github.com/scrapy/scrapy/blob/master/scrapy/core/spidermw.py#L34-L73: This is to understand how scrapy processes the different methods of the spider middleware.
• https://github.com/scrapy/scrapy/blob/master/scrapy/core/scraper.py#L135-L147: This is to understand how the scrapy core executes the spider middleware methods and passes the control to the spider callbacks.

I have simulated the above discussed code in order to write the test.

While this is solved you can use this on your settings as a workaround:

DELAY_ON_EMPTY=0.0

The problem is in frontera.contrib.scrapy.schedulers.FrontieraScheduler, method _get_next_requests. If there are no pending requests and the test self._delay_next_call < time() fails, an empty list is returned which causes the crawl to terminate

CRC32 is an unsigned 4-byte int, so it does not fit in a signed 4-byte int (Integer). There is no unsigned int type in the SQL standard, so I changed it to BigInteger instead. Without this change, both MySQL and Postgres complain that host_crc32 field value is out of bounds. Another option (to save space) would be to conver CRC32 into a signed 4-bit int, but this will complicate things, not sure it's worth it.

This is a follow up to https://github.com/scrapinghub/frontera/pull/45.

It enables the manager to receive the crawler settings and then instantiate the frontera settings accordingly. I added a few tests that should make the new behavior a little clearer.

Is something along this lines acceptable? How can it be improved?

I did everything as the document running-the-rawl, and start to run

scrapy crawl my-spider

I notice the item being crawled from the console, but I don't know whether Frontera works.

What I did

sandwarm/frontera/settings.py

BACKEND = 'frontera.contrib.backends.sqlalchemy.Distributed'

SQLALCHEMYBACKEND_ENGINE="mysql://acme:[email protected]:3306/acme"
SQLALCHEMYBACKEND_MODELS={
    'MetadataModel': 'frontera.contrib.backends.sqlalchemy.models.MetadataModel',
    'StateModel': 'frontera.contrib.backends.sqlalchemy.models.StateModel',
    'QueueModel': 'frontera.contrib.backends.sqlalchemy.models.QueueModel'
}

SPIDER_MIDDLEWARES.update({
    'frontera.contrib.scrapy.middlewares.schedulers.SchedulerSpiderMiddleware': 1000,
})

DOWNLOADER_MIDDLEWARES.update({
    'frontera.contrib.scrapy.middlewares.schedulers.SchedulerDownloaderMiddleware': 1000,
})

SCHEDULER = 'frontera.contrib.scrapy.schedulers.frontier.FronteraScheduler'

settings.py

FRONTERA_SETTINGS = 'sandwarm.frontera.settings'

Since I enable mysql backend, I am supposed to see connection error, for I don't start mysql yet.

Thanks for your guys hard working, but please make the document easier for humans. for example, a very basic working example, currently, we need to gather all documents to get the basic idea, even the worse, it still doesn't work at all. I alreay spent a week on a working example.

It's been a year since the last commit in the master branch? Do you have any plan to maintain this? I noticed a lot of issues doesn't get resolve, and lots of PR are still pending.

Getting following error when adding URL to Kafka for scrapy to parse

2020-09-07 20:12:46 [messagebus-backend] WARNING: Could not decode message: b'http://quotes.toscrape.com/page/1/', error unpack(b) received extra data.

https://github.com/scrapinghub/frontera/blob/master/frontera/core/manager.py I use 0.8.1 code base in LOCAL_MODE， The KeyError throw when running to to_fetch in StateContext class:

from line 801:

class StatesContext(object):
	...
    def to_fetch(self, requests):
        requests = requests if isinstance(requests, Iterable) else [requests]
        for request in requests:
            fingerprint = request.meta[b'fingerprint'] # error occured here!!!

I think the reason is the meta b'fingerprint' used before it's setting:

from line 302：

class LocalFrontierManager(BaseContext, StrategyComponentsPipelineMixin, BaseManager):
    def page_crawled(self, response):
...
        self.states_context.to_fetch(response)  # here used  b'fingerprint'
        self.states_context.fetch()
        self.states_context.states.set_states(response)
        super(LocalFrontierManager, self).page_crawled(response) # but only here init!
        self.states_context.states.update_cache(response)

from line 233:

class BaseManager(object):			
    def page_crawled(self, response):
...
        self._process_components(method_name='page_crawled',
                                 obj=response,
                                 return_classes=self.response_model) # b'fingerprint' will be set when pipeline go through here
		

My corrent work aroud is add the line to to_fetch method of StateContext class:

    def to_fetch(self, requests):
        requests = requests if isinstance(requests, Iterable) else [requests]
        for request in requests:
            if b'fingerprint' not in request.meta:                
                request.meta[b'fingerprint'] = sha1(request.url)
            fingerprint = request.meta[b'fingerprint']
            self._fingerprints[fingerprint] = request

What is the collect way to fix this?

Issue might be related to #337

Hi,

I have already read in discussions here, that the scheduling of requests should be done by frontera and apparently even the creation should be done by the frontier and not by the spider. However, in the documentation of scrapy and frontera it is written that requests shall be yielded in the spider parse function.

How should the process look like, if requests are to be created by the crawling strategy and not yielded by the spider? How does the spider trigger that?

In my use case, I am using scrapy-selenium with scrapy and frontera (I use SeleniumRequests to be able to wait for JS loaded elements).

I have to generate the URLs I want to scrape in two phases: I am yielding them firstly in the start_requests() method of the spider instead of a seeds file and yield requests for extracted links in the first of two parse functions.

Yielding SeleniumRequests from start_requests works, but yielding SeleniumRequests from the parse function afterwards results in the following error (only pasted an extract, as the iterable error prints the same errors over and over):

return (_set_referer(r) for r in result or ())
  File "/Users/user/opt/anaconda3/envs/frontera-update/lib/python3.8/site-packages/scrapy/core/spidermw.py", line 64, in _evaluate_iterable
    for r in iterable:
  File "/Users/user/opt/anaconda3/envs/frontera-update/lib/python3.8/site-packages/scrapy/spidermiddlewares/urllength.py", line 37, in <genexpr>
    return (r for r in result or () if _filter(r))
  File "/Users/user/opt/anaconda3/envs/frontera-update/lib/python3.8/site-packages/scrapy/core/spidermw.py", line 64, in _evaluate_iterable
    for r in iterable:
  File "/Users/user/opt/anaconda3/envs/frontera-update/lib/python3.8/site-packages/scrapy/spidermiddlewares/depth.py", line 58, in <genexpr>
    return (r for r in result or () if _filter(r))
  File "/Users/user/opt/anaconda3/envs/frontera-update/lib/python3.8/site-packages/scrapy/core/spidermw.py", line 64, in _evaluate_iterable
    for r in iterable:
  File "/Users/user/opt/anaconda3/envs/frontera-update/lib/python3.8/site-packages/frontera/contrib/scrapy/schedulers/frontier.py", line 112, in process_spider_output
    frontier_request = response.meta[b'frontier_request']
KeyError: b'frontier_request'

Very thankful for all hints and examples!