diff --git a/pom.xml b/pom.xml
index 414c27943d..4d4db226ae 100644
--- a/pom.xml
+++ b/pom.xml
@@ -3,7 +3,7 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>com.alibaba</groupId>
 	<artifactId>druid</artifactId>
-	<version>1.1.20</version>
+	<version>1.1.21_preview_01</version>
 
 
 	<packaging>jar</packaging>
@@ -21,7 +21,7 @@
 		<javadoc.skip>true</javadoc.skip>
 
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-		<jdk.version>1.6</jdk.version>
+		<jdk.version>1.8</jdk.version>
 	</properties>
 
 	<repositories>
diff --git a/src/main/java/com/alibaba/druid/VERSION.java b/src/main/java/com/alibaba/druid/VERSION.java
index 5870e4ab75..a36fe871d6 100644
--- a/src/main/java/com/alibaba/druid/VERSION.java
+++ b/src/main/java/com/alibaba/druid/VERSION.java
@@ -19,7 +19,7 @@ public final class VERSION {
 
     public final static int MajorVersion    = 1;
     public final static int MinorVersion    = 1;
-    public final static int RevisionVersion = 20;
+    public final static int RevisionVersion = 21;
 
     public static String getVersionNumber() {
         return VERSION.MajorVersion + "." + VERSION.MinorVersion + "." + VERSION.RevisionVersion;
diff --git a/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java b/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java
index 6a3aee1fd8..ae2daeddf5 100644
--- a/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java
+++ b/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java
@@ -1473,7 +1473,7 @@ public abstract class DruidAbstractDataSource extends WrapperAdapter implements
                         long mysqlIdleMillis = currentTimeMillis - lastPacketReceivedTimeMs;
                         if (lastPacketReceivedTimeMs > 0 //
                                 && mysqlIdleMillis >= timeBetweenEvictionRunsMillis) {
-                            discardConnection(conn);
+                            discardConnection(holder);
                             String errorMsg = "discard long time none received connection. "
                                     + ", jdbcUrl : " + jdbcUrl
                                     + ", jdbcUrl : " + jdbcUrl
@@ -2064,7 +2064,10 @@ public abstract class DruidAbstractDataSource extends WrapperAdapter implements
     }
     
     public abstract void discardConnection(Connection realConnection);
-    
+
+    public void discardConnection(DruidConnectionHolder holder) {
+        discardConnection(holder.getConnection());
+    }
 
     public boolean isAsyncCloseConnectionEnable() {
         if (isRemoveAbandoned()) {
diff --git a/src/main/java/com/alibaba/druid/pool/DruidConnectionHolder.java b/src/main/java/com/alibaba/druid/pool/DruidConnectionHolder.java
index f7df789d45..94ab80a3ec 100644
--- a/src/main/java/com/alibaba/druid/pool/DruidConnectionHolder.java
+++ b/src/main/java/com/alibaba/druid/pool/DruidConnectionHolder.java
@@ -68,7 +68,7 @@ public final class DruidConnectionHolder {
     protected int                                 underlyingHoldability;
     protected int                                 underlyingTransactionIsolation;
     protected boolean                             underlyingAutoCommit;
-    protected boolean                             discard                  = false;
+    protected volatile boolean                    discard                  = false;
     protected final Map<String, Object>           variables;
     protected final Map<String, Object>           globleVariables;
     final ReentrantLock                           lock                     = new ReentrantLock();
diff --git a/src/main/java/com/alibaba/druid/pool/DruidDataSource.java b/src/main/java/com/alibaba/druid/pool/DruidDataSource.java
index 6ff613ee8c..ca461599fb 100644
--- a/src/main/java/com/alibaba/druid/pool/DruidDataSource.java
+++ b/src/main/java/com/alibaba/druid/pool/DruidDataSource.java
@@ -1418,14 +1418,12 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
                         LOG.debug("skip not validate connection.");
                     }
 
-                    Connection realConnection = poolableConnection.conn;
-                    discardConnection(realConnection);
+                    discardConnection(poolableConnection.holder);
                     continue;
                 }
             } else {
-                Connection realConnection = poolableConnection.conn;
                 if (poolableConnection.conn.isClosed()) {
-                    discardConnection(null); // 传入null，避免重复关闭
+                    discardConnection(poolableConnection.holder); // 传入null，避免重复关闭
                     continue;
                 }
 
@@ -1462,7 +1460,7 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
                                 LOG.debug("skip not validate connection.");
                             }
 
-                            discardConnection(realConnection);
+                            discardConnection(poolableConnection.holder);
                              continue;
                         }
                     }
@@ -1512,6 +1510,35 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
         }
     }
 
+    public void discardConnection(DruidConnectionHolder holder) {
+        if (holder == null) {
+            return;
+        }
+
+        Connection conn = holder.getConnection();
+        if (conn != null) {
+            JdbcUtils.close(conn);
+        }
+
+        lock.lock();
+        try {
+            if (holder.discard) {
+                return;
+            }
+
+            activeCount--;
+            discardCount++;
+
+            holder.discard = true;
+
+            if (activeCount <= minIdle) {
+                emptySignal();
+            }
+        } finally {
+            lock.unlock();
+        }
+    }
+
     private DruidPooledConnection getConnectionInternal(long maxWait) throws SQLException {
         if (closed) {
             connectErrorCountUpdater.incrementAndGet(this);
@@ -1761,7 +1788,6 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
         lock.lock();
         try {
             if ((!conn.isClosed()) || !conn.isDisable()) {
-                holder.setDiscard(true);
                 conn.disable(error);
                 requireDiscard = true;
             }
@@ -1800,8 +1826,7 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
                 }
             }
 
-            this.discardConnection(holder.getConnection());
-            holder.setDiscard(true);
+            this.discardConnection(holder);
         }
 
         LOG.error("discard connection", error);
@@ -1874,7 +1899,7 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
             }
 
             if (phyMaxUseCount > 0 && holder.useCount >= phyMaxUseCount) {
-                discardConnection(holder.conn);
+                discardConnection(holder);
                 return;
             }
 
@@ -1908,7 +1933,7 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
             }
 
             if (!enable) {
-                discardConnection(holder.conn);
+                discardConnection(holder);
                 return;
             }
 
@@ -1918,7 +1943,7 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
             if (phyTimeoutMillis > 0) {
                 long phyConnectTimeMillis = currentTimeMillis - holder.connectTimeMillis;
                 if (phyConnectTimeMillis > phyTimeoutMillis) {
-                    discardConnection(holder.conn);
+                    discardConnection(holder);
                     return;
                 }
             }
@@ -1942,7 +1967,7 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
             holder.clearStatementCache();
 
             if (!holder.discard) {
-                this.discardConnection(physicalConnection);
+                discardConnection(holder);
                 holder.discard = true;
             }
 
diff --git a/src/main/java/com/alibaba/druid/util/JdbcUtils.java b/src/main/java/com/alibaba/druid/util/JdbcUtils.java
index 20a895093e..bc8b70666b 100644
--- a/src/main/java/com/alibaba/druid/util/JdbcUtils.java
+++ b/src/main/java/com/alibaba/druid/util/JdbcUtils.java
@@ -85,7 +85,12 @@ public final class JdbcUtils implements JdbcConstants {
         if (x == null) {
             return;
         }
+
         try {
+            if (x.isClosed()) {
+                return;
+            }
+
             x.close();
         } catch (Exception e) {
             LOG.debug("close connection error", e);