Package dk.netarkivet.harvester.indexserver.distribute

Class IndexRequestServer

  • All Implemented Interfaces:
    CleanupIF, HarvesterMessageVisitor, IndexRequestServerInterface, javax.jms.MessageListener
    public final class IndexRequestServer
extends HarvesterMessageHandler
implements CleanupIF, IndexRequestServerInterface
    Index request server singleton.

    This class contains a singleton that handles requesting an index over JMS.

    It will ALWAYS reply to such messages, either with the index, a message telling that only a subset is available, and which, or an error message. If the flag "settings.common.deduplication.enabled" is set to false then a request for a deduplication index will result in an empty index being returned, although the return message will claim that all requested files have been indexed.

    • Method Detail

      • getInstance

        public static IndexRequestServer getInstance()
        Get the unique index request server instance.
        Returns:
        The index request server.

      • setHandler

        public void setHandler​(RequestType t,
                       FileBasedCache<Set<Long>> handler)
        Set handler for certain type of index request. If called more than once, new handler overwrites old one.
        Specified by:
        setHandler in interface IndexRequestServerInterface
        Parameters:
        t - The type of index requested
        handler - The handler that should handle this request.

      • visit

        public void visit​(IndexRequestMessage irMsg)
           throws ArgumentNotValid
        Given a request for an index over a set of job ids, use a cache to try to create the index, Then reply result.

        If for any reason not all requested jobs can be indexed, return the subset. The client can then retry with this subset, in order to get index of that subset.

        Values read from the message in order to handle this: - Type of index requested - will use the index cache of this type - Set of job IDs - which jobs to generate index for

        Values written to message before replying: - The subset indexed - may be the entire set. ALWAYS set unless reply !OK - File with index - ONLY if subset is entire set, the index requested.

        This method should ALWAYS reply. May reply with not OK message if: - Message received was not OK - Request type is null or unknown in message - Set of job ids is null in message - Cache generation throws exception

        Specified by:
        visit in interface HarvesterMessageVisitor
        Overrides:
        visit in class HarvesterMessageHandler
        Parameters:
        irMsg - A message requesting an index.
        Throws:
        ArgumentNotValid - on null parameter

      • cleanup

        public void cleanup()
        Releases the JMS-connection and resets the singleton.
        Specified by:
        cleanup in interface CleanupIF

      • start

        public void start()
        Look for stored messages to be preprocessed, and start processing those. And start the separate thread that decides if we should listen for index-requests.
        Specified by:
        start in interface IndexRequestServerInterface