A scalable Twitter crawler module to resolve and store URL content in HBase.

Specifications:

• FetcherJobs should be run in a serial way to ensure that we adhere to the rate limits (politeness)
• we have three modules: twitter-crawler, icrawl-url-expander, icraw-injector
• the twitter crawler hands all URLs to the url expander
• the url expander has distributor, which has a chain of URL shortener plugins
• the distributor checks, if the URL has already been crawled
• if not, it is handed to the plugins
• each plugin checks, if it can handle the URL
• if not, the URL is handed over to the next plugin
• if yes, the plugin checks, if the URL is in the queue
• if not, it is added to the queue
• regularly, the top elements of the queue are queried via a service-specific API
• the expanded URLs are given to the distributor, which gives them to the injector and to the redirect archiver
• the injector puts them into the crawl db for crawling
• the redirect archiver stores the association between short URL and long URL, including metadata
• the plugin regularly checks, if there haven't been any additions to the queue and if so, resolves the URLs in the queue

What you need

• JDK 8
• Apache Nutch 2.2.1 with HBase
• nutch-injector 1.0