From 4a37a5e4a4c022101556f9d4a6b4e28985b0c82f Mon Sep 17 00:00:00 2001
From: Nikita <abracham.mitchell@gmail.com>
Date: Tue, 6 Jun 2017 13:14:43 +0300
Subject: [PATCH] dnsMonitoring turned on by default for SingleServerConfig

---
 .../redisson/config/SingleServerConfig.java   | 10 +++---
 .../connection/SingleConnectionManager.java   | 36 +++++++++++--------
 2 files changed, 27 insertions(+), 19 deletions(-)

diff --git a/redisson/src/main/java/org/redisson/config/SingleServerConfig.java b/redisson/src/main/java/org/redisson/config/SingleServerConfig.java
index 758c35422..03bc5a4dc 100644
--- a/redisson/src/main/java/org/redisson/config/SingleServerConfig.java
+++ b/redisson/src/main/java/org/redisson/config/SingleServerConfig.java
@@ -64,7 +64,7 @@ public class SingleServerConfig extends BaseConfig<SingleServerConfig> {
      * <em>NB: applications must ensure the JVM DNS cache TTL is low enough to support this.</em>
      * e.g., http://docs.aws.amazon.com/AWSSdkDocsJava/latest/DeveloperGuide/java-dg-jvm-ttl.html
      */
-    private boolean dnsMonitoring = false;
+    private boolean dnsMonitoring = true;
 
     /**
      * Interval in milliseconds to check DNS
@@ -144,8 +144,10 @@ public class SingleServerConfig extends BaseConfig<SingleServerConfig> {
 
     /**
      * Monitoring of the endpoint address for DNS changes.
-     *
-     * Default is false
+     * <p>
+     * Applications must ensure the JVM DNS cache TTL is low enough to support this
+     * <p>
+     * Default is <code>true</code>
      *
      * @param dnsMonitoring flag
      * @return config
@@ -161,7 +163,7 @@ public class SingleServerConfig extends BaseConfig<SingleServerConfig> {
     /**
      * Interval in milliseconds to check the endpoint DNS if {@link #isDnsMonitoring()} is true.
      *
-     * Default is 5000
+     * Default is <code>5000</code>
      *
      * @param dnsMonitoringInterval time
      * @return config
diff --git a/redisson/src/main/java/org/redisson/connection/SingleConnectionManager.java b/redisson/src/main/java/org/redisson/connection/SingleConnectionManager.java
index 71027b9e0..83d7c1e5c 100644
--- a/redisson/src/main/java/org/redisson/connection/SingleConnectionManager.java
+++ b/redisson/src/main/java/org/redisson/connection/SingleConnectionManager.java
@@ -93,27 +93,33 @@ public class SingleConnectionManager extends MasterSlaveConnectionManager {
     }
 
     private void monitorDnsChange(final SingleServerConfig cfg) {
-        monitorFuture = GlobalEventExecutor.INSTANCE.scheduleWithFixedDelay(new Runnable() {
+        monitorFuture = GlobalEventExecutor.INSTANCE.schedule(new Runnable() {
             @Override
             public void run() {
-                try {
-                    InetAddress master = currentMaster.get();
-                    InetAddress now = InetAddress.getByName(cfg.getAddress().getHost());
-                    if (!now.getHostAddress().equals(master.getHostAddress())) {
-                        log.info("Detected DNS change. {} has changed from {} to {}", cfg.getAddress().getHost(), master.getHostAddress(), now.getHostAddress());
-                        if (currentMaster.compareAndSet(master, now)) {
-                            changeMaster(singleSlotRange.getStartSlot(), cfg.getAddress());
-                            log.info("Master has been changed");
+                // As InetAddress.getByName call is blocking. Method should be run in dedicated thread 
+                getExecutor().execute(new Runnable() {
+                    @Override
+                    public void run() {
+                        try {
+                            InetAddress master = currentMaster.get();
+                            InetAddress now = InetAddress.getByName(cfg.getAddress().getHost());
+                            if (!now.getHostAddress().equals(master.getHostAddress())) {
+                                log.info("Detected DNS change. {} has changed from {} to {}", cfg.getAddress().getHost(), master.getHostAddress(), now.getHostAddress());
+                                if (currentMaster.compareAndSet(master, now)) {
+                                    changeMaster(singleSlotRange.getStartSlot(), cfg.getAddress());
+                                    log.info("Master has been changed");
+                                }
+                            }
+                        } catch (Exception e) {
+                            log.error(e.getMessage(), e);
+                        } finally {
+                            monitorDnsChange(cfg);
                         }
                     }
-
-                } catch (Exception e) {
-                    log.error(e.getMessage(), e);
-                }
-
+                });
             }
 
-        }, cfg.getDnsMonitoringInterval(), cfg.getDnsMonitoringInterval(), TimeUnit.MILLISECONDS);
+        }, cfg.getDnsMonitoringInterval(), TimeUnit.MILLISECONDS);
     }
 
     @Override