Frontera is an effective code hosting platform for version control and collaboration. It is a web crawling framework consisting of crawl frontier, and distribution/scaling primitives, allowing to build a large scale online web crawler. Frontera takes care of the logic and policies to follow during the crawl.
It stores and prioritises links extracted by the crawler to decide which pages to visit next, and capable of doing it in distributed manner. The frontier is initialized with a list of start URLs, that are called the seeds. Once the frontier is initialized the crawler asks it what pages should be visited next. As the crawler starts to visit the pages and obtains results, it will inform the frontier of each page response and also of the extracted hyperlinks contained within the page. These links are added by the frontier as new requests to visit according to the frontier policies.
This process (ask for new requests/notify results) is repeated until the end condition for the crawl is reached. Some crawlers may never stop, that’s what we call continuous crawls. Frontier policies can be based in almost any logic. Common use cases are usually based in score/priority systems, computed from one or many page attributes (freshness, update times, content relevance for certain terms, etc.). Crawls can also be based in really simple logics as FIFO/LIFO or DFS/BFS page visit ordering.
Depending on frontier logic, a persistent storage system may be needed to store, update or query information about the pages. Other systems can be 100% volatile and not share any information at all between different crawls. Frontera is an effective web crawling framework that will aid the user tremendously.