Posts Tagged ‘crawler’

Crawling Solr

by Karen Lynn

Recently there has been a lively discussion on Linked In’s Enterprise Search Engine Professionals Group started with this question:


“Is it an handicap for Solr to depend on third party solutions for crawling the Web like Nutch?


Our own Michael McIntosh felt compelled to respond. What follows is his post to this topic in it’s entirety.


“This topic makes me think of the saying “Write programs that do one thing and do it well.” The longer version of this philosophy, as expressed by Doug McIlroy, is this: “Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface.” Solr stands very well on its own and, based upon my impression of the Solr community so far, more people currently use Solr for structured content vs unstructured like web documents. I think that Solr should have some ‘out of the box’ web crawler implementation available, but it should not be the core focus. It can serve to allow new users of Solr to focus more on the Solr/Lucene side of things and not have to worry about rolling their own crawler or figuring out which is the best third-party crawling solution to use. I suspect that many people who need to do crawling can get by with a fairly basic crawler. My impression of Nutch so far is that is more complicated than most Solr users need out of the starting gate. That said, if you have a business that deals with large amounts of crawled unstructured content, its very likely they will need something more robust than you can reasonably ship & support as part of the Solr project. For one of our clients, the size of our dataset has grown from needed just a couple boxes, to multiple clusters with many machines each. One of the newest developments is the growth of the amount of unstructured content has grown to a size where we now need a crawler CLUSTER. When we first started on this, it never occurred to us that we might need multiple machines for the crawling side of the equation, but it has happened. But I think our case its less common. All in all, I think Solr should have a bare-bones reference implementation of a crawler that can easily be expanded upon, but it is probably not an effective use of effort to Solr developers to focus on the crawling side. Let a third party focus on the issues of crawling, it is a deceptively complicated issue.”


After his post I caught him in the office and asked where he was going with this line of thinking. “We are looking at creating a suitable enterprise crawler to replace the one provided by ESP to support customers doing a ESP to Solr migration.” He revealed. Sounds like a very promising solution to a fairly big, and common problem for companies with vast amounts of metadata. And as for unstructured content? Well, it’s the proverbial elephant in the room, don’t you think?


To see the entire conversation, with contributions from experts in the field of search architecture, click here. To get in touch with Michael directly to discuss your architecture and crawling needs, contact us.