JDK-8170910: Avoid 5 second localhost lookup behavior on OSX

[David Holmes]

Hi Nora,

This sounds like something to be discussed on net-dev at openjdk.java.net.

Thanks,
David

On 3/04/2019 8:35 am, Nora Howard wrote:
> On OSX 10.12 or later, when no mDNS services are registered, getaddrinfo
> fails on looking up localhost addresses[1]. The jdk’s current
> implementation falls back to getifaddrs after getaddrinfo fails[2]. When
> getaddrinfo fails in this way, it takes 5 seconds to fail [3]. This means
> that calls to InetAddress.getLocalHost() may take up to 5 seconds to run.
> 
> I’d like to change the jdk’s behavior in this instance so that instead of
> falling back to calling getifaddrs after getaddrinfo fails, it instead
> calls getifaddrs first if we’re on OSX and the hostname is localhost’s.
> 
> Doing this will eliminate the 5 second delay looking up localhost on
> machines with this network setup. When looking up non-localhost addresses,
> it’ll add a call to os:gethostname and a comparison.
> 
> I’d like to get some feedback about whether this approach sounds
> reasonable, and some guidance about next steps. I’ve read the “how to
> contribute” page[4], and the “code review” guide[5].
> 
> I’ve put together a patch that I’ve tested locally by turning off mDNS
> services on my local OSX machine and exercising the behavior. I’d like to
> submit patches that target dev trunk as well as the jdk 8 and 11 branches.
> 
> References
> 
> 1.
> 
>> On a Macintosh running 10.12 or later, if there are no apps that have a
>> mDNS services registered (for instance, iTunes) and there are no services
>> selected in the Sharing System Preferences, then the getaddrinfo will fail.
>>
> (https://bugs.openjdk.java.net/browse/JDK-8170910)
> 
> 2.
> http://hg.openjdk.java.net/jdk/jdk/file/cd3b7ad53265/src/java.base/unix/native/libnet/Inet6AddressImpl.c#l252
> http://hg.openjdk.java.net/jdk/jdk/file/cd3b7ad53265/src/java.base/unix/native/libnet/Inet4AddressImpl.c#l132
> (The lookupIfLocalhost function checks the passed hostname against
> os::get_host_name, and if they match, looks up via getifaddrs.)
> 
> 3. This comment describes how to reproduce the issue. I’ve reproduced it
> locally on jdk 8, 11 and 13 ea.
> https://bugs.openjdk.java.net/browse/JDK-8170910?focusedCommentId=14038262&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-14038262
> 
> 4. https://openjdk.java.net/contribute/
> 
> 5. https://openjdk.java.net/guide/codeReview.html
> 
> 
> Thanks,
> --
> Nora
>