Package org.apache.lucene.search

Class SearcherLifetimeManager

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable
    public class SearcherLifetimeManager
extends java.lang.Object
implements java.io.Closeable
    Keeps track of current plus old IndexSearchers, closing the old ones once they have timed out. Use it like this: 
       SearcherLifetimeManager mgr = new SearcherLifetimeManager();
    Per search-request, if it's a "new" search request, then obtain the latest searcher you have (for example, by using SearcherManager), and then record this searcher: 
       // Record the current searcher, and save the returend
   // token into user's search results (eg as a  hidden
   // HTML form field):
   long token = mgr.record(searcher);
    When a follow-up search arrives, for example the user clicks next page, drills down/up, etc., take the token that you saved from the previous search and: 
       // If possible, obtain the same searcher as the last
   // search:
   IndexSearcher searcher = mgr.acquire(token);
   if (searcher != null) {
     // Searcher is still here
     try {
       // do searching...
     } finally {
       mgr.release(searcher);
       // Do not use searcher after this!
       searcher = null;
     }
   } else {
     // Searcher was pruned -- notify user session timed
     // out, or, pull fresh searcher again
   }
    Finally, in a separate thread, ideally the same thread that's periodically reopening your searchers, you should periodically prune old searchers: 
       mgr.prune(new PruneByAge(600.0));

    NOTE: keeping many searchers around means you'll use more resources (open files, RAM) than a single searcher. However, as long as you are using DirectoryReader.openIfChanged(DirectoryReader), the searchers will usually share almost all segments and the added resource usage is contained. When a large merge has completed, and you reopen, because that is a large change, the new searcher will use higher additional RAM than other searchers; but large merges don't complete very often and it's unlikely you'll hit two of them in your expiration window. Still you should budget plenty of heap in the JVM to have a good safety margin.

    • Constructor Detail

      • SearcherLifetimeManager

        public SearcherLifetimeManager()

    • Method Detail

      • record

        public long record​(IndexSearcher searcher)
            throws java.io.IOException
        Records that you are now using this IndexSearcher. Always call this when you've obtained a possibly new IndexSearcher, for example from SearcherManager. It's fine if you already passed the same searcher to this method before.

        This returns the long token that you can later pass to acquire(long) to retrieve the same IndexSearcher. You should record this long token in the search results sent to your user, such that if the user performs a follow-on action (clicks next page, drills down, etc.) the token is returned.

        Throws:
        java.io.IOException

      • acquire

        public IndexSearcher acquire​(long version)
        Retrieve a previously recorded IndexSearcher, if it has not yet been closed

        NOTE: this may return null when the requested searcher has already timed out. When this happens you should notify your user that their session timed out and that they'll have to restart their search.

        If this returns a non-null result, you must match later call release(org.apache.lucene.search.IndexSearcher) on this searcher, best from a finally clause.

      • release

        public void release​(IndexSearcher s)
             throws java.io.IOException
        Release a searcher previously obtained from acquire(long).

        NOTE: it's fine to call this after close.

        Throws:
        java.io.IOException

      • prune

        public void prune​(SearcherLifetimeManager.Pruner pruner)
           throws java.io.IOException
        Calls provided SearcherLifetimeManager.Pruner to prune entries. The entries are passed to the Pruner in sorted (newest to oldest IndexSearcher) order.

        NOTE: you must peridiocally call this, ideally from the same background thread that opens new searchers.

        Throws:
        java.io.IOException

      • close

        public void close()
           throws java.io.IOException
        Close this to future searching; any searches still in process in other threads won't be affected, and they should still call release(org.apache.lucene.search.IndexSearcher) after they are done.

        NOTE: you must ensure no other threads are calling record(org.apache.lucene.search.IndexSearcher) while you call close(); otherwise it's possible not all searcher references will be freed.

        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Throws:
        java.io.IOException