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A toolkit for working with CDX indices

Project description

Build Status Coverage Status Apache License 2.0

cdx_toolkit is a set of tools for working with CDX indices of web crawls and archives, including those at CommonCrawl and the Internet Archive’s Wayback Machine.

CommonCrawl uses Ilya Kreymer’s pywb to serve the CDX API, which is somewhat different from the Internet Archive’s CDX API server. cdx_toolkit hides these differences as best it can. cdx_toolkit also knits together the monthly Common Crawl CDX indices into a single, virtual index.

Installing

cdx toolkit requires Python 3.

$ pip install cdx_toolkit

or clone this repo and use python ./setup.py install.

Example

import cdx_toolkit

cdx = cdx_toolkit.CDXFetcher(source='cc')
url = 'commoncrawl.org/*'

print(url, 'size estimate', cdx.get_size_estimate(url))

for obj in cdx.items(url, limit=1):
    print(obj)

at the moment will print:

commoncrawl.org/* size estimate 36000
{'urlkey': 'org,commoncrawl)/', 'timestamp': '20180219112308', 'mime-detected': 'text/html', 'url': 'http://commoncrawl.org/', 'status': '200', 'filename': 'crawl-data/CC-MAIN-2018-09/segments/1518891812584.40/warc/CC-MAIN-20180219111908-20180219131908-00494.warc.gz', 'mime': 'text/html', 'length': '5365', 'digest': 'FM7M2JDBADOQIHKCSFKVTAML4FL2HPHT', 'offset': '81614902'}

You can also fetch the content as bytes:

print(obj.content)

Command-line tools

$ cdx_size 'commoncrawl.org/*' --cc
$ cdx_iter 'commoncrawl.org/*' --cc --limit 10
$ cdx_iter 'commoncrawl.org/*' --cc --limit 10 --filter '=status:200'
$ cdx_size 'commoncrawl.org/*' --ia
$ cdx_iter 'commoncrawl.org/*' --ia --limit 10

cdx_iter takes a large number of command line switches, controlling the time period and all other CDX query options. cdx_iter can generate WARC, jsonl, and csv outputs.

Note that by default, cdx_iter will iterate over the previous year of captures.

See

$ cdx_iter --help

for full details. Add -v (or -vv) to see what’s going on under the hood.

CDX Jargon, Field Names, and such

cdx_toolkit supports all (ok, most!) of the options and fields discussed in the CDX API documentation:

A capture is a single crawled url, be it a copy of a webpage, a redirect to another page, an error such as 404 (page not found), or a revisit record (page identical to a previous capture.)

The url used by cdx_tools can be wildcarded in two ways. One way is *.example.com, which in CDX jargon sets matchType=’domain’, and will return captures for blog.example.com, support.example.com, etc. The other, example.com/*, will return captures for any page on example.com.

A timestmap represents year-month-day-time as a string of digits run togther. Example: January 5, 2016 at 12:34:56 UTC is 20160105123456. These timestamps are a field in the index, and are also used to pick specify the dates used by –from=, –to, and –closest on the command-line. (Programmatically, use from_ts=, to=, and closest=.)

An urlkey is a SURT, which is a munged-up url suitable for deduplication and sorting. This sort order is how CDX indices efficiently support queries like *.example.com. The SURTs for www.example.com and example.com are identical, which is handy when these 2 hosts actually have identical web content. The original url should be present in all records, if you want to know exactly what it is.

The limit argument limits how many captures will be returned. There is a default limit of 1,000 captures.

A filter allows a user to select a subset of CDX records, reducing network traffic between the CDX API server and the user. For example, filter=’!status:200’ will only show captures whose http status is not 200. Filters and limit work together, with the limit applying to the count of captures after the filter is applied. Note that revisit records have a status of ‘-‘, not 200.

CDX API servers support a paged interface for efficient access to large sets of URLs. cdx_toolkit iterators always use the paged interface. cdx_toolkit is also polite to CDX servers by being single-threaded and serial. If it’s not fast enough for you, consider downloading Common Crawl’s index files directly.

A digest is a sha1 checksum of the contents of a capture. The purpose of a digest is to be able to easily figure out if 2 captures have identical content.

Common Crawl publishes a new index each month. cdx_toolkit will start using new ones as soon as they are published. By default, cdx_toolkit will use the most recent 12 months of Common Crawl; you can change that using –from or from_ts= and –to or to=.

CDX implementations do not efficiently support reversed sort orders, so cdx_toolkit results will be ordered by ascending SURT and by ascending timestamp. However, since CC has an individual index for each month, and because most users want more recent results, cdx_toolkit defaults to querying CC’s CDX indices in decreasing month order, but each month’s result will be in ascending SURT and ascending timestamp. This default sort order is named ‘mixed’. If you’d like pure ascending, set –cc-sort or cc_sort= to ‘ascending’. You may want to also specify –from or from_ts= to set a starting timestamp.

The main problem with this ascending sort order is that it’s a pain to get the most recent N captures: –limit and limit= will return the oldest N captures. With the ‘mixed’ ordering, a large enough limit= will get close to returning the most recent N captures.

TODO

Content downloading needs help with charset issues, preferably figuring out the charset using an algorithm similar to browsers.

WARC generation should do smart(er) things with revisit records.

Right now the CC code selects which monthly CC indices to use based solely on date ranges. It would be nice to have an alternative so that a client could iterate against the most recent N CC indices, and also have the default one-year lookback use an entire monthly index instead of a partial one.

Status

cdx_toolkit has reached the beta-testing stage of development.

License

Apache 2.0

Project details


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