Frontera-SeedLoader-MongoDB

Overview

Frontera is a great framework for broad crawling, especially working with scrapy. This package provides a seed loader from MongoDB in a sync ways for frontera:

Querying seeds can be customized

Requirements

pymongo
Tests on Python 3.5
Tests on Linux, but it's a pure python module, should work on other platforms with official python and Twisted supported

Installation

The quick way:

pip install frontera-seedloader-mongodb

Or put this middleware just beside the scrapy project.

Documentation

Set Seed Loader in SPIDER_MIDDLEWARES in settings.py, for example:

# -----------------------------------------------------------------------------
# FRONTERA SEEDLOADER MONGODB ASYNC
# -----------------------------------------------------------------------------

SPIDER_MIDDLEWARES.update({
    'frontera_seedloader_mongodb.contrib.scrapy.middlewares.seeds.mongodb.MongoDBAsyncSeedLoader': 500,
})

SEEDS_MONGODB_USERNAME = 'user'
SEEDS_MONGODB_PASSWORD = 'password'
SEEDS_MONGODB_HOST = 'localhost'
SEEDS_MONGODB_PORT = 27017
SEEDS_MONGODB_DATABASE = 'test_mongodb_async_db'
SEEDS_MONGODB_COLLECTION = 'test_mongodb_async_coll'

# SEEDS_MONGODB_OPTIONS_ = 'SEEDS_MONGODB_OPTIONS_'

SEEDS_MONGODB_SEEDS_QUERY = {
    'filter': {'websites': {'$exists': 1}}
}
SEEDS_MONGODB_SEEDS_BATCH_SIZE = 1000

SEEDS_MONGODB_SEEDS_PREPARE = 'scrapy_project.utils.seeds_prepara'

Settings Reference

SEEDS_MONGODB_USERNAME

A string of the username of the database.

SEEDS_MONGODB_PASSWORD

A string of the password of the database.

SEEDS_MONGODB_HOST

A string of the ip address or the domain of the database.

SEEDS_MONGODB_PORT

A int of the port of the database.

SEEDS_MONGODB_DATABASE

A string of the name of the database.

SEEDS_MONGODB_COLLECTION

A list of the indexes to create on the collection.

SEEDS_MONGODB_OPTIONS_*

Options can be attached when the seed loader start to connect to MongoBD.

If any options are needed, the option can be set with the prefix SEEDS_MONGODB_OPTIONS_, the pipeline will parse it.

For example:

option name	in `settings.py`
authMechanism	SEEDS_MONGODB_OPTIONS_authMechanism

For more options, please refer to the page:

Connection String URI Format — MongoDB Manual 3.4

SEEDS_MONGODB_SEEDS_QUERY

A dictionary as the keyword arguments to query. The default value is:

SEEDS_MONGODB_SEEDS_QUERY = {
    'filter': None,
    'projection': None,
    'skip': 0,
    'limit': 0,
    'no_cursor_timeout': False,
    'cursor_type': CursorType.NON_TAILABLE,
    'sort': None,
    'allow_partial_results': False,
    'oplog_replay': False,
    'modifiers': None,
    'manipulate': True
}

The keys and values in this setting is followed the keyword arguments of the method find of collection in pymongo. Please refer to the following documents for more details.

collection – Collection level operations — PyMongo 3.5.1 documentation

SEEDS_MONGODB_SEEDS_BATCH_SIZE

A int of The batch size that each query will return, the default value is 100.

SEEDS_MONGODB_SEEDS_PREPARE

A string of the module path to the function to process the task (seed) from MongoDB.

The input will be the document queried from the collection set in SEEDS_MONGODB_COLLECTION, and the output should be a iterator which will return tuples with two elements: (url, doc). The url will be the argument url of Request, and the doc will be given to request.meta. As an example, the default function in this middleware:

class MongoDBSeedLoader(SeedLoader):

    ...

    def open_spider(self, spider: Spider):
        try:
            if self.settings.get(SEEDS_MONGODB_SEEDS_PREPARE):
                self.prepare = load_object(
                    self.settings.get(SEEDS_MONGODB_SEEDS_PREPARE))
            else:
                self.prepare = lambda x: map(
                    lambda y: (y, {'seed': x}),
                    x['websites'])
        except:
            raise NotConfigured

        ...

    ...

NOTE

The database drivers may have different api for the same operation, this seed loader adopts pymongo as the sync driver for MongoDB. If you want to customize this seed loader, please read the following documents for more details.

pymongo – Python driver for MongoDB

TODO

add an async way to load the seed from MongoDB
split the MongoDB to backend, make this seed load more flexible

grammy-jiang/frontera-seedloader-mongodb