Efficient storage of and access to web pages with Python

Question

So like many people I want a way to download, index/extract information and store web pages efficiently. My first thought is to use MySQL and simply shove the pages in which would let me use FULLTEXT searches which would let me do ad hoc queries easily (in case I want to see if something exists and extract it/etc.). But of course performance wise I have some concerns especially with large objects/pages and high volumes of data. So that leads me to look at things like CouchDB/search engines/etc. So to summarize, my basic requirements are:

1. It must be Python compatible (libraries/etc.)
2. Store meta data (URL, time retrieved, any GET/POST stuff I sent), response code, etc. of the page I requested.
3. Store a copy of the original web page as sent by the server (might be content, might be 404 search page, etc.).
4. Extract information from the web page and store it in a database.
5. Have the ability to do ad hoc queries on the existing corpus of original web pages (for example a new type of information I want to extract, or to see how many of the pages have the string "fizzbuzz" or whatever in them.
6. And of course it must be open source/Linux compatible, I have no interest in something I can't modify or fiddle with.

So I'm thinking several broad options are:

1. Toss everything into MySQL, use FULLTEXT, go nuts, shard the contact if needed.
2. Toss meta data into MySQL, store the data on the file system or something like CouchDB, write some custom search stuff.
3. Toss meta data into MySQL, store the data on a file system with a web server (maybe /YYYY/MM/DD/HH/MM/SS/URL/), make sure there is no default index.html/etc specified (directory index each directory in other words) and use some search engine like Lucene or Sphinx index the content and use that to search. Biggest downside I see here is the inefficiency of repeatedly crawling the site.
4. Other solutions?

When answering please include links to any technologies you mention and if possible what programming languages it has libraries for (i.e. if it's Scala only or whatever it's probably not that useful since this is a Python project). If this question has already been asked (I'm sure it must have been) please let me know (I searched, no luck).

Answer 1

It sounds to me like you need a content management system. Check out Plone. If that's not what you want maybe a web framework, like Grok, BFG, Django, Turbogears, or anything on this list. If that isn't good either, then I don't know what you are asking. :-)

Answer 2

You may be trying to achieve too much with the storage of the html (and supporting files). It seems you wish this repository would both

• allow to display a particular page as it was in its original site
• provide indexing for locating pages relevant to a particular search criteria

The html underlying a web page once looked a bit akin to a self-standing document, but the pages crawled off the net nowadays are much messier: javascript, ajax snippets, advertisement sections, image blocks etc.
This reality may cause you to rethink the one storage for all html approach. (And also the parsing / pre-processing of the material crawled, but that's another story...)

On the other hand, the distinction between metadata and the true text content associated with the page doesn't need to be so marked. By "true text content", I mean [possibly partially marked-up] text from the web pages that is otherwise free of all other "Web 2.0 noise") Many search engines, including Solr (since you mentioned Lucene) now allow mixing the two genres, in the form of semi-structured data. For operational purposes (eg to task the crawlers etc.), you may keep a relational store with management related metadata, but the idea is that for search purposes, fielded and free-text info can coexist nicely (at the cost of pre-processing much of the input data).

Answer 3

Why do you think solution (3), the Sphinx-based one, requires "repeatedly crawling the site"? Sphinx can accept and index many different data sources, including MySQL and PostgreSQL "natively" (there are contributed add-ons for other DBs such as Firebird) -- you can keep your HTML docs as columns in your DB if you like (modern PostgreSQL versions should have no trouble with that, and I imagine that MySQL's wouldn't either), just use Sphinx superior indexing and full-text search (including stemming &c). Your metadata all comes from headers, after all (plus the HTTP request body if you want to track requests in which you POSTed data, but not the HTTP response body at any rate).

One important practical consideration: I would recommend standardizing on UTF-8 -- html will come to you in all sorts of weird encodings, but there's no need to get crazy supporting that at search time -- just transcode every text page to UTF-8 upon arrival (from whatever funky encoding it came in), before storing and indexing it, and live happily ever after.

Maybe you could special-case non-textual responses to keep those in files (I can imagine that devoting gigabytes in the DB to storing e.g. videos which can't be body-indexed anyway might not be a good use of resources).

And BTW, Sphinx does come with Python bindings, as you request.