Hi all, I just committed a new implementation of venerable fetcher, called Fetcher2. It uses a producer/consumers model with a set of per-host queues. Theoretically it should be able to achieve a much higher throughput, especially for fetchlists with a lot of contention (many urls from the same hosts).
It should be possible to achieve the same fetching rate with a smaller number of threads, and most importantly to avoid the dreaded "Exceeded http.max.delays: retry later" error. It is available through "bin/nutch fetch2". From the javadoc: "A queue-based fetcher. This fetcher uses a well-known model of one producer (a QueueFeeder) and many consumers (FetcherThread-s). QueueFeeder reads input fetchlists and populates a set of FetchItemQueue-s, which hold FetchItem-s that describe the items to be fetched. There are as many queues as there are unique hosts, but at any given time the total number of fetch items in all queues is less than a fixed number (currently set to a multiple of the number of threads). As items are consumed from the queues, the QueueFeeder continues to add new input items, so that their total count stays fixed (FetcherThread-s may also add new items to the queues e.g. as a results of redirection) - until all input items are exhausted, at which point the number of items in the queues begins to decrease. When this number reaches 0 fetcher will finish. This fetcher implementation handles per-host blocking itself, instead of delegating this work to protocol-specific plugins. Each per-host queue handles its own "politeness" settings, such as the maximum number of concurrent requests and crawl delay between consecutive requests - and also a list of requests in progress, and the time the last request was finished. As FetcherThread-s ask for new items to be fetched, queues may return eligible items or null if for "politeness" reasons this host's queue is not yet ready. If there are still unfetched items on the queues, but none of the items are ready, FetcherThread-s will spin-wait until either some items become available, or a timeout is reached (at which point the Fetcher will abort, assuming the task is hung)." -- Best regards, Andrzej Bialecki <>< ___. ___ ___ ___ _ _ __________________________________ [__ || __|__/|__||\/| Information Retrieval, Semantic Web ___|||__|| \| || | Embedded Unix, System Integration http://www.sigram.com Contact: info at sigram dot com ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Nutch-developers mailing list Nutch-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nutch-developers
