Monitor Improvements LUCENE-10422

lucene/monitor/src/java/org/apache/lucene/monitor/Monitor.java

@@ -26,8 +26,6 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.concurrent.Executors;
-import java.util.concurrent.ScheduledExecutorService;
 import org.apache.lucene.analysis.Analyzer;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.index.LeafReader;
@@ -38,7 +36,6 @@
 import org.apache.lucene.search.ScoreMode;
 import org.apache.lucene.search.Scorer;
 import org.apache.lucene.search.Weight;
-import org.apache.lucene.util.NamedThreadFactory;
 
 /**
  * A Monitor contains a set of {@link Query} objects with associated IDs, and efficiently matches
@@ -51,14 +48,8 @@ public class Monitor implements Closeable {
 
   private final QueryIndex queryIndex;
 
-  private final List<MonitorUpdateListener> listeners = new ArrayList<>();
-
   private final long commitBatchSize;
 
-  private final ScheduledExecutorService purgeExecutor;
-
-  private long lastPurged = -1;
-
   /**
    * Create a non-persistent Monitor instance with the default term-filtering Presearcher
    *
@@ -100,22 +91,11 @@ public Monitor(Analyzer analyzer, Presearcher presearcher, MonitorConfiguration
 
     this.analyzer = analyzer;
     this.presearcher = presearcher;
-    this.queryIndex = new QueryIndex(configuration, presearcher);
-
-    long purgeFrequency = configuration.getPurgeFrequency();
-    this.purgeExecutor =
-        Executors.newSingleThreadScheduledExecutor(new NamedThreadFactory("cache-purge"));
-    this.purgeExecutor.scheduleAtFixedRate(
-        () -> {
-          try {
-            purgeCache();
-          } catch (Throwable e) {
-            listeners.forEach(l -> l.onPurgeError(e));
-          }
-        },
-        purgeFrequency,
-        purgeFrequency,
-        configuration.getPurgeFrequencyUnits());
+    if (configuration.isReadOnly()) {
+      this.queryIndex = new ReadonlyQueryIndex(configuration);
+    } else {
+      this.queryIndex = new WritableQueryIndex(configuration, presearcher);
+    }
 
     this.commitBatchSize = configuration.getQueryUpdateBufferSize();
   }
@@ -125,14 +105,16 @@ public Monitor(Analyzer analyzer, Presearcher presearcher, MonitorConfiguration
    * Monitor's queryindex
    *
    * @param listener listener to register
+   * @throws IllegalStateException when Monitor is readonly
    */
   public void addQueryIndexUpdateListener(MonitorUpdateListener listener) {
-    listeners.add(listener);
+    queryIndex.addListener(listener);
   }
 
   /** @return Statistics for the internal query index and cache */
-  public QueryCacheStats getQueryCacheStats() {
-    return new QueryCacheStats(queryIndex.numDocs(), queryIndex.cacheSize(), lastPurged);
+  public QueryCacheStats getQueryCacheStats() throws IOException {
+    return new QueryCacheStats(
+        queryIndex.numDocs(), queryIndex.cacheSize(), queryIndex.getLastPurged());
   }
 
   /** Statistics for the query cache and query index */
@@ -159,17 +141,17 @@ public QueryCacheStats(int queries, int cachedQueries, long lastPurged) {
    *
    * <p>This is normally called from a background thread at a rate set by configurePurgeFrequency().
    *
+   * <p>When Monitor is in read-only mode, cache is NEVER purged automatically you MUST call it when
+   * you want new changes.
+   *
    * @throws IOException on IO errors
    */
   public void purgeCache() throws IOException {
     queryIndex.purgeCache();
-    lastPurged = System.nanoTime();
-    listeners.forEach(MonitorUpdateListener::onPurge);
   }
 
   @Override
   public void close() throws IOException {
-    purgeExecutor.shutdown();
     queryIndex.close();
   }
 
@@ -192,7 +174,6 @@ public void register(Iterable<MonitorQuery> queries) throws IOException {
 
   private void commit(List<MonitorQuery> updates) throws IOException {
     queryIndex.commit(updates);
-    listeners.forEach(l -> l.afterUpdate(updates));
   }
 
   /**
@@ -213,7 +194,6 @@ public void register(MonitorQuery... queries) throws IOException {
    */
   public void deleteById(List<String> queryIds) throws IOException {
     queryIndex.deleteQueries(queryIds);
-    listeners.forEach(l -> l.afterDelete(queryIds));
   }
 
   /**
@@ -233,7 +213,6 @@ public void deleteById(String... queryIds) throws IOException {
    */
   public void clear() throws IOException {
     queryIndex.clear();
-    listeners.forEach(MonitorUpdateListener::afterClear);
   }
 
   /**
@@ -287,7 +266,7 @@ public MonitorQuery getQuery(final String queryId) throws IOException {
   }
 
   /** @return the number of queries (after decomposition) stored in this Monitor */
-  public int getDisjunctCount() {
+  public int getDisjunctCount() throws IOException {
     return queryIndex.numDocs();
   }
 

lucene/monitor/src/java/org/apache/lucene/monitor/MonitorConfiguration.java

@@ -27,6 +27,7 @@
 import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.FSDirectory;
+import org.apache.lucene.util.IOSupplier;
 
 /** Encapsulates various configuration settings for a Monitor's query index */
 public class MonitorConfiguration {
@@ -35,8 +36,9 @@ public class MonitorConfiguration {
   private long purgeFrequency = 5;
   private TimeUnit purgeFrequencyUnits = TimeUnit.MINUTES;
   private QueryDecomposer queryDecomposer = new QueryDecomposer();
-  private Path indexPath = null;
   private MonitorQuerySerializer serializer;
+  private boolean readOnly = false;
+  private IOSupplier<Directory> directoryProvider = () -> new ByteBuffersDirectory();
 
   private static IndexWriterConfig defaultIndexWriterConfig() {
     IndexWriterConfig iwc = new IndexWriterConfig(new KeywordAnalyzer());
@@ -47,16 +49,49 @@ private static IndexWriterConfig defaultIndexWriterConfig() {
     return iwc;
   }
 
+  public boolean isReadOnly() {
+    return readOnly;
+  }
+
+  public IOSupplier<Directory> getDirectoryProvider() {
+    return directoryProvider;
+  }
+
+  /**
+   * Sets a custom directory, with a custom serializer.
+   *
+   * <p>You have also the chance to configure the Monitor as read-only.
+   *
+   * @param directoryProvider lambda to provide the index Directory implementation
+   * @param serializer the serializer used to store the queries
+   * @param readOnly set the monitor as read-only
+   * @return MonitorCOnfiguration
+   */
+  public MonitorConfiguration setDirectoryProvider(
+      IOSupplier<Directory> directoryProvider,
+      MonitorQuerySerializer serializer,
+      Boolean readOnly) {
+    this.directoryProvider = directoryProvider;
+    this.serializer = serializer;
+    this.readOnly = readOnly;
+    return this;
+  }
+
+  public MonitorConfiguration setDirectoryProvider(
+      IOSupplier<Directory> directoryProvider, MonitorQuerySerializer serializer) {
+    this.directoryProvider = directoryProvider;
+    this.serializer = serializer;
+    return this;
+  }
+
   public MonitorConfiguration setIndexPath(Path indexPath, MonitorQuerySerializer serializer) {
-    this.indexPath = indexPath;
     this.serializer = serializer;
+    this.directoryProvider = () -> FSDirectory.open(indexPath);
     return this;
   }
 
   public IndexWriter buildIndexWriter() throws IOException {
-    Directory directory =
-        indexPath == null ? new ByteBuffersDirectory() : FSDirectory.open(indexPath);
-    return new IndexWriter(directory, getIndexWriterConfig());
+    return new IndexWriter(directoryProvider.get(), getIndexWriterConfig());
   }
 
   protected IndexWriterConfig getIndexWriterConfig() {