Clear Cache Each Iteration: The DNS Cache Manager caches the IP address -> the DNS hostname pairs and returns the cached value if the DNS hostname has a match in its internal cache. If this checkbox is ticked, the cache will be cleared at the start of the thread.
Use System DNS Resolver: The DNS Cache Manager will query DNS Server(s) defined in your OS network configuration in order to determine the hostname for each thread representing virtual users. In this case, you need to override the networkaddress.cache.ttl property in the $JAVA_HOME/jre/lib/security/java.security file and set it to 0 (the property defaults to “-1” which stands for “forever”)
Use Custom DNS Resolver: You can specify one or more DNS servers in the list.
If more than one server is provided, the DNS Cache Manager will choose a random one for each call – and will run as a round-robin mechanism.
If nothing is provided, the system DNS resolver will be used (the DNS server/s defined in your OS network configuration).
The DNS Cache Manager – Quick Tips and Troubleshooting
1. Where to put the DNS Cache Manager
The DNS Cache Manager should be added as a child of the Test Plan or a Thread Group element.
2. Always Use HTTPClient4
Make sure that you have HTTPClient4 selected in “Implementation” drop-down
3. Enable Logging
It’s easy to enable logging on the DNS Cache Manager. Just append the following parameter to the JMeter startup script:
-Ljmeter.protocol.http.control.DNSCacheManager=DEBUG
as
java -jar ApacheJMeter.jar -Ljmeter.protocol.http.control.DNSCacheManager=DEBUG
or
jmeter.bat -Ljmeter.protocol.http.control.DNSCacheManager=DEBUG