diff --git a/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceRecoverThread.java b/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceRecoverThread.java
index 38249e024e..7ea818ae77 100644
--- a/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceRecoverThread.java
+++ b/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceRecoverThread.java
@@ -31,7 +31,8 @@ import java.sql.Connection;
 public class RandomDataSourceRecoverThread implements Runnable {
     private final static Log LOG = LogFactory.getLog(RandomDataSourceRecoverThread.class);
     private RandomDataSourceSelector selector;
-    private int sleepSeconds = 30;
+    private int sleepSeconds = 60;
+    private int validationSleepSeconds = 0;
 
     public RandomDataSourceRecoverThread(RandomDataSourceSelector selector) {
         this.selector = selector;
@@ -61,6 +62,7 @@ public class RandomDataSourceRecoverThread implements Runnable {
         Connection connection = null;
         try {
             connection = dataSource.getConnection();
+            sleepBeforeValidation();
             dataSource.validateConnection(connection);
             LOG.info(dataSource.getName() + " is available now.");
             selector.removeBlacklist(dataSource);
@@ -75,6 +77,17 @@ public class RandomDataSourceRecoverThread implements Runnable {
         }
     }
 
+    private void sleepBeforeValidation() {
+        if (validationSleepSeconds > 0) {
+            try {
+                LOG.debug("Sleep " + validationSleepSeconds + " second(s) before validation.");
+                Thread.sleep(validationSleepSeconds * 1000);
+            } catch (InterruptedException e) {
+                // ignore
+            }
+        }
+    }
+
     private void sleep() {
         try {
             Thread.sleep(sleepSeconds * 1000);
@@ -90,4 +103,12 @@ public class RandomDataSourceRecoverThread implements Runnable {
     public void setSleepSeconds(int sleepSeconds) {
         this.sleepSeconds = sleepSeconds;
     }
+
+    public int getValidationSleepSeconds() {
+        return validationSleepSeconds;
+    }
+
+    public void setValidationSleepSeconds(int validationSleepSeconds) {
+        this.validationSleepSeconds = validationSleepSeconds;
+    }
 }
diff --git a/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelector.java b/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelector.java
index fac6ba65a2..434e30cfbe 100644
--- a/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelector.java
+++ b/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelector.java
@@ -51,7 +51,7 @@ public class RandomDataSourceSelector implements DataSourceSelector {
     private RandomDataSourceRecoverThread recoverThread;
 
     private int checkingIntervalSeconds = 15;
-    private int recoveryIntervalSeconds = 30;
+    private int recoveryIntervalSeconds = 60;
     private int validationSleepSeconds = 0;
     private int blacklistThreshold = 3;
 
@@ -118,6 +118,10 @@ public class RandomDataSourceSelector implements DataSourceSelector {
         return blacklist;
     }
 
+    public boolean containInBlacklist(DataSource dataSource) {
+        return dataSource != null && blacklist.contains(dataSource);
+    }
+
     public void addBlacklist(DataSource dataSource) {
         if (dataSource != null && !blacklist.contains(dataSource)) {
             blacklist.add(dataSource);
@@ -128,7 +132,7 @@ public class RandomDataSourceSelector implements DataSourceSelector {
     }
 
     public void removeBlacklist(DataSource dataSource) {
-        if (dataSource != null && blacklist.contains(dataSource)) {
+        if (containInBlacklist(dataSource)) {
             blacklist.remove(dataSource);
             if (dataSource instanceof DruidDataSource) {
                 ((DruidDataSource) dataSource).setTestOnReturn(highAvailableDataSource.isTestOnReturn());
@@ -161,14 +165,19 @@ public class RandomDataSourceSelector implements DataSourceSelector {
     }
 
     private void initThreads() {
-        validateThread = new RandomDataSourceValidateThread(this);
-        validateThread.setCheckingIntervalSeconds(checkingIntervalSeconds);
-        validateThread.setValidationSleepSeconds(validationSleepSeconds);
-        validateThread.setBlacklistThreshold(blacklistThreshold);
-        new Thread(validateThread, "RandomDataSourceSelector-isValid-thread").start();
+        if (validateThread == null) {
+            validateThread = new RandomDataSourceValidateThread(this);
+            validateThread.setCheckingIntervalSeconds(checkingIntervalSeconds);
+            validateThread.setValidationSleepSeconds(validationSleepSeconds);
+            validateThread.setBlacklistThreshold(blacklistThreshold);
+        }
+        new Thread(validateThread, "RandomDataSourceSelector-validate-thread").start();
 
-        recoverThread = new RandomDataSourceRecoverThread(this);
-        recoverThread.setSleepSeconds(recoveryIntervalSeconds);
+        if (recoverThread == null) {
+            recoverThread = new RandomDataSourceRecoverThread(this);
+            recoverThread.setSleepSeconds(recoveryIntervalSeconds);
+            recoverThread.setValidationSleepSeconds(validationSleepSeconds);
+        }
         new Thread(recoverThread, "RandomDataSourceSelector-recover-thread").start();
     }
 
diff --git a/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceValidateThread.java b/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceValidateThread.java
index 9beca1e65d..8a11096c93 100644
--- a/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceValidateThread.java
+++ b/src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceValidateThread.java
@@ -89,7 +89,8 @@ public class RandomDataSourceValidateThread implements Runnable {
         for (Map.Entry<String, Integer> e : errorCounts.entrySet()) {
             if (e.getValue() <= 0) {
                 selector.removeBlacklist(dataSourceMap.get(e.getKey()));
-            } else if (e.getValue() >= blacklistThreshold) {
+            } else if (e.getValue() >= blacklistThreshold
+                    && !selector.containInBlacklist(dataSourceMap.get(e.getKey()))) {
                 LOG.warn("Adding " + e.getKey() + " to blacklist.");
                 selector.addBlacklist(dataSourceMap.get(e.getKey()));
             }
@@ -105,6 +106,11 @@ public class RandomDataSourceValidateThread implements Runnable {
                 continue;
             }
 
+            if (selector.containInBlacklist(e.getValue())) {
+                LOG.debug(e.getKey() + " is already in blacklist, skip.");
+                continue;
+            }
+
             tasks.add(new Callable<Boolean>() {
                 @Override
                 public Boolean call() {
diff --git a/src/test/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelectorTest.java b/src/test/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelectorTest.java
index c37b2337b6..a2b88d7468 100644
--- a/src/test/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelectorTest.java
+++ b/src/test/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelectorTest.java
@@ -40,6 +40,7 @@ public class RandomDataSourceSelectorTest extends BaseRandomDataSourceSelectorTe
 
         assertEquals(10, selector.getValidationSleepSeconds());
         assertEquals(10, selector.getValidateThread().getValidationSleepSeconds());
+        assertEquals(10, selector.getRecoverThread().getValidationSleepSeconds());
 
         assertEquals(5, selector.getBlacklistThreshold());
         assertEquals(5, selector.getValidateThread().getBlacklistThreshold());
diff --git a/src/test/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelectorWithValidationTest.java b/src/test/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelectorWithValidationTest.java
index 13a7a5421c..50c284818f 100644
--- a/src/test/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelectorWithValidationTest.java
+++ b/src/test/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelectorWithValidationTest.java
@@ -31,13 +31,13 @@ public class RandomDataSourceSelectorWithValidationTest {
     @Test
     public void testOneDataSourceFailAndRecover() throws Exception {
         RandomDataSourceSelector selector = ((RandomDataSourceSelector) highAvailableDataSource.getDataSourceSelector());
-        selector.setCheckingIntervalSeconds(3);
+        selector.getValidateThread().setCheckingIntervalSeconds(3);
         selector.getRecoverThread().setSleepSeconds(3);
         selector.init();
 
         DruidDataSource dataSource = (DruidDataSource) highAvailableDataSource.getDataSourceMap().get("foo");
         dataSource.setValidationQuery("select xxx from yyy");
-        Thread.sleep(6 * 1000);
+        Thread.sleep(10 * 1000);
         assertTrue(dataSource.isTestOnReturn());
         for (int i = 0; i < 100; i++) {
             assertNotEquals(dataSource, selector.get());