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

[Michael McMahon]

Hi Nora,

At first sight, the approach sounds reasonable to me. I'd like to see 
the patch
and also do you have detailed instructions on how to reproduce the issue 
(the 5 second delay)?

Thanks,
Michael.

On 03/04/2019, 17:46, Nora Howard wrote:
> I'd initially sent this to jdk-dev, but I was asked to move it to net-dev.
>
> 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 
> <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
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