The thing with ELBs is they expect external systems to handle which server to use (maybe the OS or the application stack). So you'll get different results in different situations. If you run:
`dig +short yourelbaddress a` you'll see the servers the elb is using sent back - this is the pure ELB response, beyond this it's up to whatever layer of logic is making that request to manage how this is cached or not, or who knows what. I can confirm that the java param you mentioned does not make a difference. I will see all my traffic routed to one box if I run jmeter on a single server and point it to an ELB no matter if I include this or not. I suspect that the option is working, that the dns response is not cached, but that maybe it is getting the same result each time and simply takes the first option given to it - but I'm not certain In any case, 2 options: 1. Don't use the ELB and go direct to the servers and balance the traffic yourself in your testplan. 2. Use multiple machines to run jmeter. Option 1 is a bad idea as you want to test the ELBs - they are a known potential bottleneck for very high loads. Option 2 is better but you'll need to setup a distributed network of test machines. On 31 Jan 2013, at 15:40, sebb <[email protected]> wrote: > On 31 January 2013 14:30, Ben Litchfield <[email protected]> wrote: >> I'm having an issue with getting jmeter to refresh it's DNS cache >> >> JRE 1.7 >> >> I'm attempting to do some load testing against an amazon ELB. The ELB >> is pre-warmed and has 8 ip addresses >> >> for example >> >> nslookup mylb.us-east-1.elb.amazonaws.com >> Addresses: x.x.x.98 >> x.x.x.87 >> x.x.x.164 >> x.x.x.96 >> x.x.x.143 >> x.x.x.186 >> x.x.x.85 >> x.x.x.75 >> >> But when I run my test it only ever uses a single ip address. >> >> I'm using a SOAP/XML-RPC Request KeepAlive=False and as its running I >> call "netstat -n -a" to see what IP it's connecting to. For a test >> run it only uses a single ip address. When I restart JMeter it will >> start using a new ip address. >> >> I reviewed on the web and have attempted to set >> networkaddress.cache.ttl=0 sun.net.inetaddr.ttl=0 in all recommended >> locations >> >> 1)adding -Dsun.net.inetaddr.ttl=0 to JVM_ARGS >> jmeter -q test.properties -t UnloadedPolling-5000.jmx java.exe >> -XX:+HeapDumpOnOutOfMemoryError -Xms512m -Xmx512m -XX:NewSize=128m >> XX:MaxNewSize=128m -XX:SurvivorRatio=8 -XX:TargetSurvivorRatio=50 >> -XX:MaxTenuringThreshold=2 -Dsun.rmi.dgc.client.gcInterval=600000 >> -sun.rmi.dgc.server.gcInterval=600000 -XX:PermSize=64m >> -XX:MaxPermSize=64m -Dsun.net.inetaddr.ttl=0 -jar >> "C:\javalib\apache-jmeter-2.8\bin\ApacheJMeter.jar" -q test.properties >> -t UnloadedPolling-5000.jmx >> >> 2)Adding the below to test.properties (note above command line) >> networkaddress.cache.ttl=0 >> sun.net.inetaddr.ttl=0 >> >> 3)Updated JRE\lib\security\java.security >> networkaddress.cache.ttl=0 >> >> But it still only uses a single address. >> >> Any additional thoughts? > > The OS might also cache. > >> Thanks, >> Ben >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: [email protected] >> For additional commands, e-mail: [email protected] >> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > > --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
