Specifies the java class used for the frontier (a list of URLs not yet visited).

Key: crawler.classes.Frontier
Type: String
Can be set in: collection.cfg


The web crawler’s frontier is the queue of URLs that are waiting to be processed. The following are the main frontier types available:

  • Supports sending multiple parallel requests to servers as specified in a site_profiles.cfg file. This frontier is the default.

  • Uses separate queues for each host.

  • This is a first-in first-out (FIFO) management scheme. Using this frontier allows the crawler to create multiple simultaneous connections to a target host. Note: This can generate heavy load on a target web server.

Default Value

This specifies that a MultipleRequestsFrontier should be used, which in turn makes use of disk-based FIFOFrontiers of size 1000 each. Here size refers to the number of URLs per frontier i.e. in the example above each disk-based FIFOFrontier will store up to 1000 URLs each. When a frontier fills up a new one will be created so that all the URLs in the entire frontier are stored in a chain of backing frontiers.

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