Index: lucene/facet/src/java/org/apache/lucene/facet/taxonomy/SearcherTaxonomyManager.java
===================================================================
--- lucene/facet/src/java/org/apache/lucene/facet/taxonomy/SearcherTaxonomyManager.java	(revision 1562788)
+++ lucene/facet/src/java/org/apache/lucene/facet/taxonomy/SearcherTaxonomyManager.java	(working copy)
@@ -22,6 +22,7 @@
 import org.apache.lucene.facet.taxonomy.directory.DirectoryTaxonomyReader;
 import org.apache.lucene.facet.taxonomy.directory.DirectoryTaxonomyWriter;
 import org.apache.lucene.index.DirectoryReader;
+import org.apache.lucene.index.IndexNotFoundException;
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.search.IndexSearcher;
@@ -28,6 +29,7 @@
 import org.apache.lucene.search.ReferenceManager;
 import org.apache.lucene.search.SearcherFactory;
 import org.apache.lucene.search.SearcherManager;
+import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.IOUtils;
 
 /**
@@ -69,11 +71,27 @@
     this.searcherFactory = searcherFactory;
     this.taxoWriter = taxoWriter;
     DirectoryTaxonomyReader taxoReader = new DirectoryTaxonomyReader(taxoWriter);
-    current = new SearcherAndTaxonomy(SearcherManager.getSearcher(searcherFactory, DirectoryReader.open(writer, applyAllDeletes)),
-                                      taxoReader);
-    taxoEpoch = taxoWriter.getTaxonomyEpoch();
+    current = new SearcherAndTaxonomy(SearcherManager.getSearcher(searcherFactory, DirectoryReader.open(writer, applyAllDeletes)), taxoReader);
+    this.taxoEpoch = taxoWriter.getTaxonomyEpoch();
   }
 
+  /**
+   * Creates search and taxonomy readers over the corresponding directories.
+   * Note that you should only initialize the manage after both the search and
+   * taxonomy indexes were created, otherwise you will hit
+   * {@link IndexNotFoundException}.
+   */
+  public SearcherTaxonomyManager(Directory indexDir, Directory taxoDir, SearcherFactory searcherFactory) throws IOException {
+    if (searcherFactory == null) {
+      searcherFactory = new SearcherFactory();
+    }
+    this.searcherFactory = searcherFactory;
+    DirectoryTaxonomyReader taxoReader = new DirectoryTaxonomyReader(taxoDir);
+    current = new SearcherAndTaxonomy(SearcherManager.getSearcher(searcherFactory, DirectoryReader.open(indexDir)), taxoReader);
+    this.taxoWriter = null;
+    taxoEpoch = -1;
+  }
+
   @Override
   protected void decRef(SearcherAndTaxonomy ref) throws IOException {
     ref.searcher.getIndexReader().decRef();
@@ -114,7 +132,7 @@
       if (tr == null) {
         ref.taxonomyReader.incRef();
         tr = ref.taxonomyReader;
-      } else if (taxoWriter.getTaxonomyEpoch() != taxoEpoch) {
+      } else if (taxoWriter != null && taxoWriter.getTaxonomyEpoch() != taxoEpoch) {
         IOUtils.close(newReader, tr);
         throw new IllegalStateException("DirectoryTaxonomyWriter.replaceTaxonomy was called, which is not allowed when using SearcherTaxonomyManager");
       }
Index: lucene/facet/src/test/org/apache/lucene/facet/taxonomy/TestSearcherTaxonomyManager.java
===================================================================
--- lucene/facet/src/test/org/apache/lucene/facet/taxonomy/TestSearcherTaxonomyManager.java	(revision 1562788)
+++ lucene/facet/src/test/org/apache/lucene/facet/taxonomy/TestSearcherTaxonomyManager.java	(working copy)
@@ -42,7 +42,8 @@
 import org.apache.lucene.util._TestUtil;
 
 public class TestSearcherTaxonomyManager extends FacetTestCase {
-  public void test() throws Exception {
+  
+  public void testNRT() throws Exception {
     Directory dir = newDirectory();
     Directory taxoDir = newDirectory();
     final IndexWriter w = new IndexWriter(dir, newIndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer(random())));
@@ -160,8 +161,108 @@
 
     IOUtils.close(mgr, tw, w, taxoDir, dir);
   }
+  
+  public void testDirectory() throws Exception {
+    Directory indexDir = newDirectory();
+    Directory taxoDir = newDirectory();
+    final IndexWriter w = new IndexWriter(indexDir, newIndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer(random())));
+    final DirectoryTaxonomyWriter tw = new DirectoryTaxonomyWriter(taxoDir);
+    // first empty commit
+    w.commit();
+    tw.commit();
+    final SearcherTaxonomyManager mgr = new SearcherTaxonomyManager(indexDir, taxoDir, null);
+    final FacetsConfig config = new FacetsConfig();
+    config.setMultiValued("field", true);
+    final AtomicBoolean stop = new AtomicBoolean();
 
-  public void testReplaceTaxonomy() throws Exception {
+    // How many unique facets to index before stopping:
+    final int ordLimit = TEST_NIGHTLY ? 100000 : 6000;
+
+    Thread indexer = new Thread() {
+      @Override
+      public void run() {
+        try {
+          Set<String> seen = new HashSet<String>();
+          List<String> paths = new ArrayList<String>();
+          while (true) {
+            Document doc = new Document();
+            int numPaths = _TestUtil.nextInt(random(), 1, 5);
+            for(int i=0;i<numPaths;i++) {
+              String path;
+              if (!paths.isEmpty() && random().nextInt(5) != 4) {
+                // Use previous path
+                path = paths.get(random().nextInt(paths.size()));
+              } else {
+                // Create new path
+                path = null;
+                while (true) {
+                  path = _TestUtil.randomRealisticUnicodeString(random());
+                  if (path.length() != 0 && !seen.contains(path)) {
+                    seen.add(path);
+                    paths.add(path);
+                    break;
+                  }
+                }
+              }
+              doc.add(new FacetField("field", path));
+            }
+            try {
+              w.addDocument(config.build(tw, doc));
+              if (random().nextDouble() < 0.1) {
+                w.commit();
+                tw.commit();
+                mgr.maybeRefresh();
+              }
+            } catch (IOException ioe) {
+              throw new RuntimeException(ioe);
+            }
+            
+            if (tw.getSize() >= ordLimit) {
+              break;
+            }
+          }
+        } finally {
+          stop.set(true);
+        }
+      }
+    };
+
+    indexer.start();
+
+    try {
+      while (!stop.get()) {
+        SearcherAndTaxonomy pair = mgr.acquire();
+        try {
+          //System.out.println("search maxOrd=" + pair.taxonomyReader.getSize());
+          FacetsCollector sfc = new FacetsCollector();
+          pair.searcher.search(new MatchAllDocsQuery(), sfc);
+          Facets facets = getTaxonomyFacetCounts(pair.taxonomyReader, config, sfc);
+          FacetResult result = facets.getTopChildren(10, "field");
+          if (pair.searcher.getIndexReader().numDocs() > 0) { 
+            //System.out.println(pair.taxonomyReader.getSize());
+            assertTrue(result.childCount > 0);
+            assertTrue(result.labelValues.length > 0);
+          }
+
+          //if (VERBOSE) {
+          //System.out.println("TEST: facets=" + FacetTestUtils.toString(results.get(0)));
+          //}
+        } finally {
+          mgr.release(pair);
+        }
+      }
+    } finally {
+      indexer.join();
+    }
+
+    if (VERBOSE) {
+      System.out.println("TEST: now stop");
+    }
+
+    IOUtils.close(mgr, tw, w, taxoDir, indexDir);
+  }
+  
+  public void testReplaceTaxonomyNRT() throws Exception {
     Directory dir = newDirectory();
     Directory taxoDir = newDirectory();
     IndexWriter w = new IndexWriter(dir, newIndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer(random())));
@@ -185,4 +286,43 @@
 
     IOUtils.close(mgr, tw, w, taxoDir, dir);
   }
+  
+  public void testReplaceTaxonomyDirectory() throws Exception {
+    Directory indexDir = newDirectory();
+    Directory taxoDir = newDirectory();
+    IndexWriter w = new IndexWriter(indexDir, newIndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer(random())));
+    DirectoryTaxonomyWriter tw = new DirectoryTaxonomyWriter(taxoDir);
+    w.commit();
+    tw.commit();
+
+    Directory taxoDir2 = newDirectory();
+    DirectoryTaxonomyWriter tw2 = new DirectoryTaxonomyWriter(taxoDir2);
+    tw2.addCategory(new FacetLabel("a", "b"));
+    tw2.close();
+
+    SearcherTaxonomyManager mgr = new SearcherTaxonomyManager(indexDir, taxoDir, null);
+    SearcherAndTaxonomy pair = mgr.acquire();
+    try {
+      assertEquals(1, pair.taxonomyReader.getSize());
+    } finally {
+      mgr.release(pair);
+    }
+    
+    w.addDocument(new Document());
+    tw.replaceTaxonomy(taxoDir2);
+    taxoDir2.close();
+    w.commit();
+    tw.commit();
+
+    mgr.maybeRefresh();
+    pair = mgr.acquire();
+    try {
+      assertEquals(3, pair.taxonomyReader.getSize());
+    } finally {
+      mgr.release(pair);
+    }
+
+    IOUtils.close(mgr, tw, w, taxoDir, indexDir);
+  }
+
 }