InetAddress should utilize networkaddress.cache.ttl for getLocalHost() too (original) (raw)

Deven You youdwei at linux.vnet.ibm.com
Wed Jul 11 23:59:32 PDT 2012

Hi Alan and Michael,

Thanks very much for your kind suggestions.

I agree that local host shouldn't follow the default caching mechanism because the IP may change frequently. And I also think making the cache time configurable is a better solution.

I am willing to make these changes including adding the local host caching mechanism into the java doc.

I have gone through the related code for InetAddress.java and InetAddressCachePolicy.java. And I think we could add a new security property networkaddress.cache.localhost.ttl to achieve the goal.

As far as I know, to add networkaddress.cache.localhost.ttl I need change jdk/src/share/lib/security/java.security*(include java.security, java.security-solaris, java.security-macosx and java.security-windows). Please correct me if I have any misunderstanding.

Here I have one question need your help: the static block in InetAddressCachePolicy.java will first try to get cachePolicyProp/negativeCachePolicyProp from System properties. If one of the cache values is null then the value of cachePolicyPropFallback/negativeCachePolicyProp would be got from System properties. I don't know where we declare these fallback properties so I have no idea where I can do the same thing for networkaddress.cache.localhost.ttl.

Please take a look.

Thanks a lot!

On 07/11/2012 06:55 PM, Michael McMahon wrote:

On 11/07/12 08:00, Alan Bateman wrote:

On 05/07/2012 07:10, Deven You wrote:

Hi All,

I noticed that InetAddress.getLocalHost() uses cache to improve the performance. However the default implementation is caching local host within 5 seconds. From the spec, networkaddress.cache.ttl should be used to control the cache behaviour and I think it is a better solution. For example, if the networkaddress.cache.ttl is set to -1 which means always cache the local host then we can avoid unnecessary operations on getAddressesFromNameService to improve the performance. I have made a patch for this solution, so anyone would like to take a look? [1] http://cr.openjdk.java.net/~littlee/OJDK-527/webrev.00/ <http://cr.openjdk.java.net/%7Elittlee/OJDK-527/webrev.00/> Thanks a lot! -- Best Regards, Deven I'm not sure about this one as I suspect it will cause problems in DHCP or any environments where the host addresses changes, say moving to a different wireless network or waking up a machine after hibernation. -Alan That's true. We updated the spec for the caching behavior a while back, and probably should have included this exception for the local host. I agree that we shouldn't change the behavior. Perhaps, the 5 seconds could be configurable itself, but I think it should be kept separate from the main caching behavior. - Michael.

-- Best Regards,

Deven

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