ensure Engine.close() is called

h2/src/main/org/h2/engine/Database.java

@@ -1256,6 +1256,7 @@ public class Database implements DataHandler {
      *            hook
      */
     void close(boolean fromShutdownHook) {
+        try {
             synchronized (this) {
                 if (closing) {
                     return;
@@ -1270,7 +1271,6 @@ public class Database implements DataHandler {
                         // ignore
                     }
                     traceSystem.close();
-                Engine.getInstance().close(databaseName);
                     return;
                 }
                 closing = true;
@@ -1350,7 +1350,6 @@ public class Database implements DataHandler {
                 }
                 closeOnExit = null;
             }
-        Engine.getInstance().close(databaseName);
             if (deleteFilesOnDisconnect && persistent) {
                 deleteFilesOnDisconnect = false;
                 try {
@@ -1361,6 +1360,9 @@ public class Database implements DataHandler {
                     // ignore (the trace is closed already)
                 }
             }
+        } finally {
+            Engine.getInstance().close(databaseName);
+        }
     }
 
     private void removeOrphanedLobs() {

h2/src/main/org/h2/engine/Engine.java

@@ -5,7 +5,7 @@
  */
 package org.h2.engine;
 
-import java.util.Hashtable;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 import org.h2.api.ErrorCode;
@@ -28,7 +28,7 @@ import org.h2.util.Utils;
 public class Engine implements SessionFactory {
 
     private static final Engine INSTANCE = new Engine();
-    private static final Map<String, Database> DATABASES = new Hashtable<>();
+    private static final Map<String, Database> DATABASES = new HashMap<>();
 
     private volatile long wrongPasswordDelay =
             SysProperties.DELAY_WRONG_PASSWORD_MIN;
@@ -51,13 +51,14 @@ public class Engine implements SessionFactory {
         Database database;
         ci.removeProperty("NO_UPGRADE", false);
         boolean openNew = ci.getProperty("OPEN_NEW", false);
+        boolean opened = false;
+        User user = null;
+        synchronized (DATABASES) {
             if (openNew || ci.isUnnamedInMemory()) {
                 database = null;
             } else {
                 database = DATABASES.get(name);
             }
-        User user = null;
-        boolean opened = false;
             if (database == null) {
                 if (ifExists && !Database.exists(name)) {
                     throw DbException.get(ErrorCode.DATABASE_NOT_FOUND_1, name);
@@ -77,6 +78,7 @@ public class Engine implements SessionFactory {
                     DATABASES.put(name, database);
                 }
             }
+        }
         if (opened) {
             // start the thread when already synchronizing on the database
             // otherwise a deadlock can occur when the writer thread
@@ -273,8 +275,10 @@ public class Engine implements SessionFactory {
                 throw DbException.get(ErrorCode.FEATURE_NOT_SUPPORTED_1, e, "JMX");
             }
         }
+        synchronized (DATABASES) {
             DATABASES.remove(name);
         }
+    }
 
     /**
      * This method is called after validating user name and password. If user

h2/src/test/org/h2/test/db/TestOutOfMemory.java

@@ -118,10 +118,7 @@ public class TestOutOfMemory extends TestBase {
                         ErrorCode.DATABASE_IS_CLOSED == e.getErrorCode() ||
                         ErrorCode.GENERAL_ERROR_1 == e.getErrorCode());
             }
-            for (int i = 0; i < 5; i++) {
-                System.gc();
-                Thread.sleep(20);
-            }
+            recoverAfterOOM();
             try {
                 conn.close();
                 fail();
@@ -132,10 +129,7 @@ public class TestOutOfMemory extends TestBase {
                         ErrorCode.DATABASE_IS_CLOSED == e.getErrorCode() ||
                         ErrorCode.GENERAL_ERROR_1 == e.getErrorCode());
             }
-            for (int i = 0; i < 5; i++) {
-                System.gc();
-                Thread.sleep(20);
-            }
+            recoverAfterOOM();
             conn = DriverManager.getConnection(url);
             stat = conn.createStatement();
             stat.execute("SELECT 1");
@@ -146,14 +140,18 @@ public class TestOutOfMemory extends TestBase {
         }
     }
 
-    private void testUpdateWhenNearlyOutOfMemory() throws SQLException, InterruptedException {
-        if (config.memory) {
-            return;
-        }
+    private static void recoverAfterOOM() throws InterruptedException {
         for (int i = 0; i < 5; i++) {
             System.gc();
             Thread.sleep(20);
         }
+    }
+
+    private void testUpdateWhenNearlyOutOfMemory() throws SQLException, InterruptedException {
+        if (config.memory) {
+            return;
+        }
+        recoverAfterOOM();
         deleteDb("outOfMemory");
         Connection conn = getConnection("outOfMemory;MAX_OPERATION_MEMORY=1000000");
         Statement stat = conn.createStatement();
@@ -171,11 +169,12 @@ public class TestOutOfMemory extends TestBase {
                 fail();
             } catch(DbException ex) {
                 freeMemory();
-                assertEquals(ErrorCode.OUT_OF_MEMORY, ex.getErrorCode());
+                assertTrue(ErrorCode.OUT_OF_MEMORY == ex.getErrorCode() || ErrorCode.GENERAL_ERROR_1 == ex.getErrorCode());
             } catch (SQLException ex) {
                 freeMemory();
-                assertEquals(ErrorCode.OUT_OF_MEMORY, ex.getErrorCode());
+                assertTrue(ErrorCode.OUT_OF_MEMORY == ex.getErrorCode() || ErrorCode.GENERAL_ERROR_1 == ex.getErrorCode());
             }
+            recoverAfterOOM();
             try {
                 conn.close();
                 fail();