Package org.apache.lucene.index

Class ConcurrentMergeScheduler

  • All Implemented Interfaces:
    Closeable, AutoCloseable, Cloneable
    public class ConcurrentMergeScheduler
extends MergeScheduler
    A MergeScheduler that runs each merge using a separate thread.

    Specify the max number of threads that may run at once, and the maximum number of simultaneous merges with setMaxMergesAndThreads(int, int).

    If the number of merges exceeds the max number of threads then the largest merges are paused until one of the smaller merges completes.

    If more than getMaxMergeCount() merges are requested then this class will forcefully throttle the incoming threads by pausing until one more more merges complete.

    • Field Detail

      • DEFAULT_MAX_THREAD_COUNT

        public static final int DEFAULT_MAX_THREAD_COUNT
        Default maxThreadCount. We default to 1: tests on spinning-magnet drives showed slower indexing performance if more than one merge thread runs at once (though on an SSD it was faster)
        See Also:
        Constant Field Values

      • DEFAULT_MAX_MERGE_COUNT

        public static final int DEFAULT_MAX_MERGE_COUNT
        Default maxMergeCount.
        See Also:
        Constant Field Values

    • Constructor Detail

      • ConcurrentMergeScheduler

        public ConcurrentMergeScheduler()
        Sole constructor, with all settings set to default values.

    • Method Detail

      • setMaxMergesAndThreads

        public void setMaxMergesAndThreads​(int maxMergeCount,
                                   int maxThreadCount)
        Sets the maximum number of merge threads and simultaneous merges allowed.
        Parameters:
        maxMergeCount - the max # simultaneous merges that are allowed. If a merge is necessary yet we already have this many threads running, the incoming thread (that is calling add/updateDocument) will block until a merge thread has completed. Note that we will only run the smallest maxThreadCount merges at a time.
        maxThreadCount - the max # simultaneous merge threads that should be running at once. This must be <= maxMergeCount

      • getMergeThreadPriority

        public int getMergeThreadPriority()
        Return the priority that merge threads run at. By default the priority is 1 plus the priority of (ie, slightly higher priority than) the first thread that calls merge.

      • setMergeThreadPriority

        public void setMergeThreadPriority​(int pri)
        Set the base priority that merge threads run at. Note that CMS may increase priority of some merge threads beyond this base priority. It's best not to set this any higher than Thread.MAX_PRIORITY-maxThreadCount, so that CMS has room to set relative priority among threads.

      • sync

        public void sync()
        Wait for any running merge threads to finish. This call is not interruptible as used by close().