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  1. JDK
  2. JDK-8175982

Enabling JMX silently causes the disabling of the JVM's DNS cache to not work

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      Description

      FULL PRODUCT VERSION :
      openjdk version "1.8.0_121"
      OpenJDK Runtime Environment (build 1.8.0_121-8u121-b13-0ubuntu1.16.04.2-b13)
      OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode)

      ADDITIONAL OS VERSION INFORMATION :
      Linux hostname 4.4.0-62-generic #83-Ubuntu SMP Wed Jan 18 14:10:15 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

      A DESCRIPTION OF THE PROBLEM :
      When I disable the JVM's DNS cache (line 8 of MakeTwoDnsRequests.java), and then make two DNS requests, then using Wireshark I can see two DNS requests are made.

      However, upon enabling JMX, when I re-do the same test, I can only see one DNS request.

      It's as if the disabling of the DNS cache silently failed.

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      (You might need to run tshark and kill as root)

      ```
      $ javac MakeTwoDnsRequests.java
      $ tshark -i any -f "src port 53" -Y "dns.qry.type eq 1" -n -T fields -e dns.qry.name -e dns.a > without-jmx.txt 2>/dev/null &
      [1] 17460
      $ java MakeTwoDnsRequests
      $ kill 17460
      $ cat without-jmx.txt
      www.example.com 93.184.216.34
      www.example.com 93.184.216.34
      $
      $ tshark -i any -f "src port 53" -Y "dns.qry.type eq 1" -n -T fields -e dns.qry.name -e dns.a > with-jmx.txt 2>/dev/null &
      [1] 17495
      $ java -Dcom.sun.management.jmxremote MakeTwoDnsRequests
      $ kill 17495
      $ cat with-jmx.txt
      ```

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      I expect DNS requests are sent:

      ```
      $ cat with-jmx.txt
      www.example.com 93.184.216.34
      www.example.com 93.184.216.34
      ```
      ACTUAL -
      But only one DNS request is sent:

      ```
      $ cat with-jmx.txt
      www.example.com 93.184.216.34
      ```

      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      import java.security.Security;
      import java.net.InetAddress;

      public class MakeTwoDnsRequests {

      public static void main(String[] args) throws Exception {
      // Disable JVM DNS caching
      Security.setProperty("networkaddress.cache.ttl", "0");

      System.out.println(InetAddress.getByName("www.example.com").getHostAddress());
      System.out.println(InetAddress.getByName("www.example.com").getHostAddress());
      }
      }
      ---------- END SOURCE ----------

      CUSTOMER SUBMITTED WORKAROUND :
      For Hotspot, specify sun.net.inetaddr.ttl=0 when starting the JVM:

      ```
      $ java -Dsun.net.inetaddr.ttl=0 -Dcom.sun.management.jmxremote MakeTwoDnsRequests
      ```

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            • Assignee:
              fmatte Fairoz Matte
              Reporter:
              webbuggrp Webbug Group
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              • Created:
                Updated:
                Resolved: