diff --git a/core/src/main/java/org/apache/sqoop/audit/AuditLoggerManager.java b/core/src/main/java/org/apache/sqoop/audit/AuditLoggerManager.java
index 5e5d7abb..af9282c2 100644
--- a/core/src/main/java/org/apache/sqoop/audit/AuditLoggerManager.java
+++ b/core/src/main/java/org/apache/sqoop/audit/AuditLoggerManager.java
@@ -63,7 +63,7 @@ public static AuditLoggerManager getInstance() {
     return instance;
   }
 
-  public AuditLoggerManager() {
+  private AuditLoggerManager() {
     loggers = new ArrayList<AuditLogger>();
   }
 
@@ -122,10 +122,11 @@ private void initializeLoggers() {
   }
 
   public synchronized void destroy() {
+    loggers = null;
     LOG.trace("Begin audit logger manager destroy");
   }
 
-  public void logAuditEvent(String username,
+  public synchronized void logAuditEvent(String username,
       String ip, String operation, String objectType, String objectId) {
     for (AuditLogger logger : loggers) {
       logger.logAuditEvent(username, ip, operation, objectType, objectId);
@@ -133,7 +134,7 @@ public void logAuditEvent(String username,
   }
 
   @Override
-  public void configurationChanged() {
+  public synchronized void configurationChanged() {
     LOG.info("Begin audit logger manager reconfiguring");
     initializeLoggers();
     LOG.info("Audit logger manager reconfigured");
diff --git a/core/src/main/java/org/apache/sqoop/audit/FileAuditLogger.java b/core/src/main/java/org/apache/sqoop/audit/FileAuditLogger.java
index 42cb330a..49a380c7 100644
--- a/core/src/main/java/org/apache/sqoop/audit/FileAuditLogger.java
+++ b/core/src/main/java/org/apache/sqoop/audit/FileAuditLogger.java
@@ -41,22 +41,10 @@ public class FileAuditLogger extends AuditLogger {
    */
   private Logger logger;
 
-  /**
-   * Configurations for this audit logger
-   */
-  private Map<String, String> config;
-
-  /**
-   * Properties to setup logger
-   */
-  private Properties props;
-
-  public FileAuditLogger() {
-    this.props = new Properties();
-  }
+  public FileAuditLogger() {}
 
   public void initialize() {
-    config = getLoggerConfig();
+    Map<String, String> config = getLoggerConfig();
 
     String outputFile = config.get(FILE);
     if (outputFile == null) {
@@ -66,6 +54,7 @@ public void initialize() {
     // setup logger
     String appender = "log4j.appender." + getLoggerName() + APPENDER_SURFIX;
     LOG.warn("appender: " + appender);
+    Properties props = new Properties();
     props.put(appender, "org.apache.log4j.RollingFileAppender");
     props.put(appender + ".File", outputFile);
     props.put(appender + ".layout", "org.apache.log4j.PatternLayout");
diff --git a/core/src/main/java/org/apache/sqoop/connector/ConnectorManager.java b/core/src/main/java/org/apache/sqoop/connector/ConnectorManager.java
index b64d6fdc..5f269aa7 100644
--- a/core/src/main/java/org/apache/sqoop/connector/ConnectorManager.java
+++ b/core/src/main/java/org/apache/sqoop/connector/ConnectorManager.java
@@ -67,6 +67,11 @@ public class ConnectorManager implements Reconfigurable {
     instance = new ConnectorManager();
   }
 
+  /**
+   * The private constructor for the singleton class.
+   */
+  private ConnectorManager() {}
+
   /**
    * Return current instance.
    *
diff --git a/core/src/main/java/org/apache/sqoop/core/SqoopConfiguration.java b/core/src/main/java/org/apache/sqoop/core/SqoopConfiguration.java
index 04da05f0..52e432dd 100644
--- a/core/src/main/java/org/apache/sqoop/core/SqoopConfiguration.java
+++ b/core/src/main/java/org/apache/sqoop/core/SqoopConfiguration.java
@@ -68,6 +68,11 @@ public class SqoopConfiguration implements Reconfigurable {
     instance = new SqoopConfiguration();
   }
 
+  /**
+   * The private constructor for the singleton class.
+   */
+  private SqoopConfiguration() {}
+
   /**
    * Return current instance.
    *
diff --git a/core/src/main/java/org/apache/sqoop/driver/Driver.java b/core/src/main/java/org/apache/sqoop/driver/Driver.java
index 8d490dd5..cff2bef2 100644
--- a/core/src/main/java/org/apache/sqoop/driver/Driver.java
+++ b/core/src/main/java/org/apache/sqoop/driver/Driver.java
@@ -110,7 +110,7 @@ public Class getDriverJobConfigurationClass() {
       return JobConfiguration.class;
   }
 
-  public Driver() {
+  private Driver() {
     List<MConfig> driverConfig = ConfigUtils.toConfigs(getDriverJobConfigurationClass());
     mDriver = new MDriver(new MDriverConfig(driverConfig), DriverBean.CURRENT_DRIVER_VERSION);
 
diff --git a/core/src/main/java/org/apache/sqoop/driver/JobManager.java b/core/src/main/java/org/apache/sqoop/driver/JobManager.java
index fdd48f1f..87c6c748 100644
--- a/core/src/main/java/org/apache/sqoop/driver/JobManager.java
+++ b/core/src/main/java/org/apache/sqoop/driver/JobManager.java
@@ -72,6 +72,11 @@ public class JobManager implements Reconfigurable {
     instance = new JobManager();
   }
 
+  /**
+   * The private constructor for the singleton class.
+   */
+  private JobManager() {}
+
   /**
    * Return current instance.
    *
diff --git a/core/src/main/java/org/apache/sqoop/repository/RepositoryManager.java b/core/src/main/java/org/apache/sqoop/repository/RepositoryManager.java
index 121f388d..fd623401 100644
--- a/core/src/main/java/org/apache/sqoop/repository/RepositoryManager.java
+++ b/core/src/main/java/org/apache/sqoop/repository/RepositoryManager.java
@@ -48,6 +48,11 @@ public class RepositoryManager implements Reconfigurable {
     instance = new RepositoryManager();
   }
 
+  /**
+   * The private constructor for the singleton class.
+   */
+  private RepositoryManager() {}
+
   /**
    * Return current instance.
    *
diff --git a/core/src/main/java/org/apache/sqoop/security/AuthenticationManager.java b/core/src/main/java/org/apache/sqoop/security/AuthenticationManager.java
index 6b12e9f6..1d6d94d5 100644
--- a/core/src/main/java/org/apache/sqoop/security/AuthenticationManager.java
+++ b/core/src/main/java/org/apache/sqoop/security/AuthenticationManager.java
@@ -46,7 +46,7 @@ public class AuthenticationManager implements Reconfigurable {
   }
 
   /**
-   * The private constructor for the singleton class,
+   * The private constructor for the singleton class.
    */
   private AuthenticationManager(){}
 
diff --git a/core/src/test/java/org/apache/sqoop/driver/TestJobManager.java b/core/src/test/java/org/apache/sqoop/driver/TestJobManager.java
index 203d8b0f..414d3e91 100644
--- a/core/src/test/java/org/apache/sqoop/driver/TestJobManager.java
+++ b/core/src/test/java/org/apache/sqoop/driver/TestJobManager.java
@@ -51,7 +51,7 @@ public class TestJobManager {
 
   @BeforeMethod(alwaysRun = true)
   public void setUp() {
-    jobManager = new JobManager();
+    jobManager = JobManager.getInstance();
     connectorMgrMock = mock(ConnectorManager.class);
     sqoopConnectorMock = mock(SqoopConnector.class);
     ConnectorManager.setInstance(connectorMgrMock);