Merge pull request #15458 from cdapio/develop-fix-ip-caching

[CDAP-20781] fix issue where service ip is cached forever

cdap-app-fabric/src/main/java/io/cdap/cdap/internal/app/runtime/distributed/AbstractProgramTwillRunnable.java

@@ -96,6 +96,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.slf4j.bridge.SLF4JBridgeHandler;
+import sun.net.InetAddressCachePolicy;
 
 /**
  * A {@link TwillRunnable} for running a program through a {@link ProgramRunner}.
@@ -172,6 +173,16 @@ private void doInitialize(File programOptionFile) throws Exception {
     controllerFuture = new CompletableFuture<>();
     programCompletion = new CompletableFuture<>();
 
+    // Make sure InetAddressCachePolicy is not set to FOREVER.
+    // This is needed because if InetAddressCachePolicy is loaded after System#setSecurityManager() call,
+    // caching policy is set to FOREVER. With FOREVER, caching policy, this twill runnable will not be able to
+    // reach out to other services within the cluster as IP is cached forever.
+    // Look at CDAP-20781 for more information.
+    if (InetAddressCachePolicy.get() == InetAddressCachePolicy.FOREVER) {
+      LOG.warn("InetAddress cache policy is set to FOREVER. This will ips to be cached forever. "
+              + "Ensure cache policy is not set to FOREVER.");
+    }
+
     // Setup process wide settings
     Thread.setDefaultUncaughtExceptionHandler(new UncaughtExceptionHandler());
     System.setSecurityManager(new ProgramContainerSecurityManager(System.getSecurityManager()));