Class SearcherLifetimeManager

Keeps track of current plus old IndexSearchers, disposing 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 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 runtime to have a good safety margin.

Inheritance
object
SearcherLifetimeManager
Implements
Inherited Members
Namespace: Lucene.Net.Search
Assembly: Lucene.Net.dll
Syntax
public class SearcherLifetimeManager : IDisposable

Methods

Acquire(long)

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(IndexSearcher) on this searcher, best from a finally clause.

Declaration
public virtual IndexSearcher Acquire(long version)
Parameters
Type Name Description
long version
Returns
Type Description
IndexSearcher

Dispose()

Close this to future searching; any searches still in process in other threads won't be affected, and they should still call Release(IndexSearcher) after they are done.

NOTE: you must ensure no other threads are calling Record(IndexSearcher) while you call Dispose(); otherwise it's possible not all searcher references will be freed.
Declaration
public void Dispose()

Dispose(bool)

Releases resources used by the SearcherLifetimeManager and if overridden in a derived class, optionally releases unmanaged resources.

Declaration
protected virtual void Dispose(bool disposing)
Parameters
Type Name Description
bool disposing

true to release both managed and unmanaged resources; false to release only unmanaged resources.

Prune(IPruner)

Calls provided SearcherLifetimeManager.IPruner to prune entries. The entries are passed to the SearcherLifetimeManager.IPruner in sorted (newest to oldest IndexSearcher) order.

NOTE: you must peridiocally call this, ideally from the same background thread that opens new searchers.
Declaration
public virtual void Prune(SearcherLifetimeManager.IPruner pruner)
Parameters
Type Name Description
SearcherLifetimeManager.IPruner pruner

Record(IndexSearcher)

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.

Declaration
public virtual long Record(IndexSearcher searcher)
Parameters
Type Name Description
IndexSearcher searcher
Returns
Type Description
long

Release(IndexSearcher)

Release a searcher previously obtained from Acquire(long).

NOTE: it's fine to call this after Dispose().
Declaration
public virtual void Release(IndexSearcher s)
Parameters
Type Name Description
IndexSearcher s

Implements