InMemory and MapDB connectors now implement AutoCloseable and close c…

…onnections on JVM shutdown. A close() method is added in the Trainable interface, responsible for releasing algorithm's resources. Removed modifiesData() method from trainable, no algorithm should modify the Dataset internally (if it does it should copy the dataset). Update tests to close() the instances.

TODO.txt

@@ -1,9 +1,6 @@
 CODE IMPROVEMENTS
 =================
 
-- Do we need close() in models and dataset etc?
-- Make sure the connector is closed automatically if not closed manually?
-
 - Improve Serialization by setting the serialVersionUID in every serializable class?
 - Create better Exceptions and Exception messages.
 - Add multithreading support.

src/main/java/com/datumbox/applications/nlp/CETR.java

@@ -217,6 +217,7 @@ private void performClustering(Dataset dataset, int numberOfClusters) {
         //Map<Integer, BaseMLclusterer.Cluster> clusters = instance.getClusters();
 
         instance.erase(); //erase immediately the result
+        instance = null;
     }
 
     private List<Double> calculateTTRlist(List<String> rows) {

src/main/java/com/datumbox/common/dataobjects/Dataset.java

@@ -498,10 +498,7 @@ public void erase() {
         dbc.dropBigMap("tmp_xColumnTypes", xDataTypes);
         dbc.dropBigMap("tmp_recordList", recordList);
         dbc.dropDatabase();
-
-        dbName = null;
-        dbc = null;
-        dbConf = null;
+        dbc.close();
 
         //Ensures that the Dataset can't be used after erase() is called.
         yDataType = null;

src/main/java/com/datumbox/common/objecttypes/Trainable.java

@@ -48,16 +48,14 @@ public interface Trainable<MP extends Learnable, TP extends Parameterizable> {
      * @param trainingParameters
      */
     public void fit(Dataset trainingData, TP trainingParameters);
-
-    /**
-     * Returns whether the algorithm modifies the provided data.
-     * 
-     * @return 
-     */
-    public boolean modifiesData();
 
     /**
      * Deletes the database of the algorithm. 
      */
     public void erase();
+
+    /**
+     * Closes all the resources of the algorithm. 
+     */
+    public void close();
 }

src/main/java/com/datumbox/common/persistentstorage/AutoCloseConnector.java

@@ -0,0 +1,70 @@
+/**
+ * Copyright (C) 2013-2015 Vasilis Vryniotis <bbriniotis@datumbox.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.datumbox.common.persistentstorage;
+
+import com.datumbox.common.persistentstorage.interfaces.DatabaseConnector;
+
+/**
+ * Any class that inherits from the abstract AutoCloseConnector class can be used
+ * in a try-with-resources statement block. Moreover this class setups a shutdown
+ * hook which ensures that the Connector will automatically call close() before the
+ * JVM is terminated.
+ * 
+ * @author Vasilis Vryniotis <bbriniotis@datumbox.com>
+ */
+public abstract class AutoCloseConnector implements DatabaseConnector, AutoCloseable {
+
+    private boolean isClosed = false;
+
+    /**
+     * Protected Constructor which is responsible for adding the Shutdown hook.
+     */
+    protected AutoCloseConnector() {
+        Runtime.getRuntime().addShutdownHook(new Thread() {
+            @Override
+            public void run() {
+                AutoCloseConnector.this.close();
+            }
+        });
+    }
+
+    /**
+     * Checks if the connector is closed.
+     * 
+     * @return 
+     */
+    @Override
+    public boolean isClosed() {
+        return isClosed;
+    }
+
+    /**
+     * Marks the connector as closed.
+     */
+    @Override
+    public void close() {
+        isClosed = true;
+    }
+
+    /**
+     * Ensures the connection is not closed.
+     */
+    protected void ensureNotClosed() {
+        if(isClosed) {
+            throw new RuntimeException("The connector is already closed");
+        }
+    }
+}

src/main/java/com/datumbox/common/persistentstorage/inmemory/InMemoryConnector.java

@@ -15,6 +15,7 @@
  */
 package com.datumbox.common.persistentstorage.inmemory;
 
+import com.datumbox.common.persistentstorage.AutoCloseConnector;
 import com.datumbox.common.persistentstorage.interfaces.DatabaseConnector;
 import java.io.File;
 import java.io.IOException;
@@ -37,7 +38,7 @@
  *
  * @author Vasilis Vryniotis <bbriniotis@datumbox.com>
  */
-public class InMemoryConnector implements DatabaseConnector {
+public class InMemoryConnector extends AutoCloseConnector {
 
     private final InMemoryConfiguration dbConf;
     private final String database;
@@ -50,6 +51,7 @@ public class InMemoryConnector implements DatabaseConnector {
      * @param dbConf 
      */
     protected InMemoryConnector(String database, InMemoryConfiguration dbConf) {  
+        super();
         this.dbConf = dbConf;
         this.database = database;
     }
@@ -64,6 +66,7 @@ protected InMemoryConnector(String database, InMemoryConfiguration dbConf) {
      */
     @Override
     public <T extends Serializable> void save(String name, T serializableObject) {
+        ensureNotClosed();
         try { 
             Files.write(getDefaultPath(), DeepCopy.serialize(serializableObject));
         } 
@@ -83,6 +86,7 @@ public <T extends Serializable> void save(String name, T serializableObject) {
     @Override
     @SuppressWarnings("unchecked")
     public <T extends Serializable> T load(String name, Class<T> klass) {
+        ensureNotClosed();
         try { 
             //read the stored serialized object
             T serializableObject = (T)DeepCopy.deserialize(Files.readAllBytes(getDefaultPath()));
@@ -101,7 +105,10 @@ public <T extends Serializable> T load(String name, Class<T> klass) {
      */
     @Override
     public void close() {
-        //nothing to do
+        if(isClosed()){
+            return; 
+        }
+        super.close();
     }
 
     /**
@@ -111,6 +118,7 @@ public void close() {
      */
     @Override
     public boolean existsDatabase() {
+        ensureNotClosed();
         return Files.exists(getDefaultPath());
     }
 
@@ -119,6 +127,7 @@ public boolean existsDatabase() {
      */
     @Override
     public void dropDatabase() {
+        ensureNotClosed();
         if(!existsDatabase()) {
             return;
         }
@@ -143,6 +152,7 @@ public void dropDatabase() {
      */
     @Override
     public <K,V> Map<K,V> getBigMap(String name, boolean isTemporary) {
+        ensureNotClosed();
         return new HashMap<>();
     }  
 
@@ -155,6 +165,7 @@ public <K,V> Map<K,V> getBigMap(String name, boolean isTemporary) {
      */
     @Override
     public <T extends Map> void dropBigMap(String name, T map) {
+        ensureNotClosed();
         map.clear();
     } 
 

src/main/java/com/datumbox/common/persistentstorage/interfaces/DatabaseConnector.java

@@ -15,7 +15,6 @@
  */
 package com.datumbox.common.persistentstorage.interfaces;
 
-import java.io.Closeable;
 import java.io.Serializable;
 import java.util.Map;
 
@@ -27,7 +26,7 @@
  * 
  * @author Vasilis Vryniotis <bbriniotis@datumbox.com>
  */
-public interface DatabaseConnector extends Closeable {
+public interface DatabaseConnector {
 
     /**
      * This method is responsible for storing serializable objects in the
@@ -52,9 +51,15 @@ public interface DatabaseConnector extends Closeable {
     /**
      * Closes the connection and clean ups the resources.
      */
-    @Override
     public void close();
 
+    /**
+     * Checks if the connector is closed.
+     * 
+     * @return 
+     */
+    public boolean isClosed();
+
     /**
      * Checks if a particular database exists.
      * 

src/main/java/com/datumbox/common/persistentstorage/mapdb/MapDBConnector.java

@@ -15,7 +15,7 @@
  */
 package com.datumbox.common.persistentstorage.mapdb;
 
-import com.datumbox.common.persistentstorage.interfaces.DatabaseConnector;
+import com.datumbox.common.persistentstorage.AutoCloseConnector;
 import java.io.File;
 import java.io.IOException;
 import java.nio.file.FileSystems;
@@ -39,7 +39,7 @@
  *
  * @author Vasilis Vryniotis <bbriniotis@datumbox.com>
  */
-public class MapDBConnector implements DatabaseConnector {
+public class MapDBConnector extends AutoCloseConnector {
 
     /**
      * Enum class which stores the Database Type used for every collection.
@@ -66,6 +66,7 @@ private enum DatabaseType {
      * @param dbConf 
      */
     protected MapDBConnector(String database, MapDBConfiguration dbConf) {  
+        super();
         this.dbConf = dbConf;
         this.database = database;
     }
@@ -80,6 +81,7 @@ protected MapDBConnector(String database, MapDBConfiguration dbConf) {
      */
     @Override
     public <T extends Serializable> void save(String name, T serializableObject) {
+        ensureNotClosed();
         openDB(DatabaseType.DEFAULT_DB);
         DB db = dbRegistry.get(DatabaseType.DEFAULT_DB);
         Atomic.Var<T> knowledgeBaseVar = db.getAtomicVar(name);
@@ -99,6 +101,7 @@ public <T extends Serializable> void save(String name, T serializableObject) {
     @Override
     @SuppressWarnings("unchecked")
     public <T extends Serializable> T load(String name, Class<T> klass) {
+        ensureNotClosed();
         openDB(DatabaseType.DEFAULT_DB);
         DB db = dbRegistry.get(DatabaseType.DEFAULT_DB);
         Atomic.Var<T> atomicVar = db.getAtomicVar(name);
@@ -110,12 +113,11 @@ public <T extends Serializable> T load(String name, Class<T> klass) {
      */
     @Override
     public void close() {
-        //close all dbs stored in dbRegistry
-        for(DB db : dbRegistry.values()) {
-            if(isOpenDB(db)) {
-                db.close();
-            }
+        if(isClosed()){
+            return; 
         }
+        super.close();
+        closeAllDBs();
     }
 
     /**
@@ -125,6 +127,7 @@ public void close() {
      */
     @Override
     public boolean existsDatabase() {
+        ensureNotClosed();
         if(Files.exists(getDefaultPath())) {
             return true;
         }
@@ -143,13 +146,14 @@ public boolean existsDatabase() {
      */
     @Override
     public void dropDatabase() {
+        ensureNotClosed();
         if(!existsDatabase()) {
             return;
         }
 
-        try {
-            close();
+        closeAllDBs();
 
+        try {
             dbRegistry.clear();
             Files.deleteIfExists(getDefaultPath());
             Files.deleteIfExists(Paths.get(getDefaultPath().toString()+".p"));
@@ -172,6 +176,7 @@ public void dropDatabase() {
      */
     @Override
     public <K,V> Map<K,V> getBigMap(String name, boolean isTemporary) {
+        ensureNotClosed();
         validateName(name, isTemporary);
 
         DatabaseType dbType = isTemporary?DatabaseType.TEMP_DB:DatabaseType.DEFAULT_DB;
@@ -191,6 +196,7 @@ public <K,V> Map<K,V> getBigMap(String name, boolean isTemporary) {
      */
     @Override
     public <T extends Map> void dropBigMap(String name, T map) {
+        ensureNotClosed();
         boolean isTemporary = existsInDB(dbRegistry.get(DatabaseType.TEMP_DB), name); 
 
         DatabaseType dbType = isTemporary?DatabaseType.TEMP_DB:DatabaseType.DEFAULT_DB;
@@ -203,6 +209,15 @@ public <T extends Map> void dropBigMap(String name, T map) {
 
     //private methods of connector class
 
+    private void closeAllDBs() {
+        //close all dbs stored in dbRegistry
+        for(DB db : dbRegistry.values()) {
+            if(isOpenDB(db)) {
+                db.close();
+            }
+        }
+    }
+
     private boolean isOpenDB(DB db) {
         return !(db == null || db.isClosed());
     }

src/main/java/com/datumbox/framework/machinelearning/common/bases/BaseTrainable.java

@@ -82,6 +82,11 @@ public void erase() {
         knowledgeBase.erase();
     }
 
+    @Override
+    public void close() {
+        knowledgeBase.close();
+    }
+
     @Override
      public MP getModelParameters() {
        return knowledgeBase.getModelParameters();
@@ -100,12 +105,6 @@ public void fit(Dataset trainingData, TP trainingParameters) {
         knowledgeBase.save();
     }
 
-    @Override
-    public boolean modifiesData() {
-        //If the algorithm modifies the data it should override this method
-        return false;
-    }
-
     protected void initializeTrainingConfiguration(TP trainingParameters) {
         //reset knowledge base
         knowledgeBase.reinitialize();